title: XCOM: Enemy Unknown

text: The game can be played on higher difficulty levels: Classic (in a reference to the original game) and Impossible, each with the option to enable the "Ironman" option (which limits players to a single save file) separately for each. Jake Solomon, lead developer, stated on numerous occasions that he believes that the "truest "XCOM" experience" is playing without the ability to reload saved games. On the higher difficulty levels, the random nature of battles, where soldiers under the player's command can permanently die from one enemy attack, the against-all-odds nature of combat against the unknown and technologically superior enemy, and the requirement to sacrifice some resources – including soldiers and even entire countries – for the greater good combine to create a bleak atmosphere where the player feels the weight of command.


title: XCOM: Enemy Unknown

text: The game features a multiplayer mode for one-on-one tactical battles. Players spend a predefined points budget on assembling a squad of up to six humans, aliens, or a mixture of both. Human units are customizable in terms of weaponry, armor and gadgets. A simplified version of the single-player perk system is present. Alien units may not be customized but possess the abilities of corresponding aliens types in the single-player mode of the game.


title: XCOM: Enemy Unknown

text: Psionic combat from the original 1994 game is retained, but some gameplay features of the original have been removed or adapted. The time units system, the always-visible grid map and the inventory system of the original have been removed. The initial mission phase of disembarking from the transport has also been removed – missions now begin with troops deployed outside the craft. Unlike in the 1994 game, only one XCOM base exists, the location of which is chosen at the beginning of the game.


title: XCOM: Enemy Unknown

text: Although there are some differences in the interface between platforms, unlike other games such as Firaxis' "Civilization Revolution", the content is not simplified for the console versions. The PC version features a mouse-driven UI.


title: XCOM: Enemy Unknown

text: The game's campaign begins in the spring of 2015, as a global alien invasion begins. Prior to the start of the game, a group of countries called the Council of Nations has banded together to create XCOM (short for Extraterrestrial Combat Unit), the most elite military and scientific organization in human history, tasked with defending them from the alien attack. The player assumes the role of the commander of XCOM, and proceeds to engage in a war against an extraterrestrial enemy with overwhelming technological superiority.


title: XCOM: Enemy Unknown

text: In March 2015, a series of extraterrestrial objects land in a major German city. A squad of four soldiers is sent to investigate the incident. Upon entering a warehouse, the squad finds German soldiers being mind controlled by a small alien creature before being ambushed. All but one of the soldiers are killed before the area is secured. Alien attacks begin all over the globe.


title: XCOM: Enemy Unknown

text: After success with shooting down alien scout ships and securing the crash sites from surviving alien crews, as well as interdicting alien attempts to abduct human civilians for unknown purposes, XCOM manages to also obtain the corpses of various different alien troops. Autopsies reveal that all these types have been genetically and/or cybernetically altered, which seems to indicate they are merely foot-soldiers for unseen leaders. XCOM's head of research, Dr. Vahlen, requests that a live alien be captured for interrogation. This also involves developing a specialized weapon capable of capturing a live alien, and constructing a facility in XCOM's subterranean base capable of safely holding a live alien prisoner.


title: XCOM: Enemy Unknown

text: Capturing one of the alien troops and conducting the interrogation reveals vague information about another type of alien called the Outsiders, artificially-created crystalline beings encountered aboard UFOs, that appear to serve as pilots and navigators. Dr. Vahlen then requests that XCOM capture an Outsider for study. Upon capturing one of these, the examination reveals that the Outsiders' exotic crystalline structures behave in a manner similar to antennas, receiving a signal broadcast from a location buried underground on Earth. XCOM dispatches a team to investigate the signal; it is found to be coming from a base that the aliens have secretly established on Earth, where experiments are performed on abducted humans.


title: XCOM: Enemy Unknown

text: XCOM develops a method for gaining entry to the alien base and assaults it. During the mission, the alien serving as the base commander is discovered to have psychic abilities, but is nevertheless defeated by the soldiers. The commander's psychic communication device is recovered and reverse engineered. Tapping into the aliens' communications reveals a previously hidden, stealth "Overseer" UFO making rounds across the Earth. When the UFO is shot down, it is found to hold an alien species that had not been previously encountered, as well as a strange psionic artifact. The newly discovered species, called Ethereals, possess powerful psionic abilities.


title: XCOM: Enemy Unknown

text: Once the Overseer ship is shot down and the psionic artifact recovered, the massive enemy "Temple Ship" reveals itself in low Earth orbit over Brazil, and starts causing earthquakes even as far away as XCOM HQ. The reverse-engineering efforts enable XCOM to unlock and develop latent psionic powers that are present in certain human beings, thus enhancing their human soldiers. Out of these psychic human soldiers, the most powerful becomes the Volunteer, using the psionic artifact recovered from the Overseer UFO to tap into the aliens' psychic communication "hive", an experience that also increases his or her psionic strength. This allows them to attack and board the Temple Ship to seek out the Uber Ethereal, the leader of the alien invasion.


title: XCOM: Enemy Unknown

text: During the final battle aboard the ship, the Uber Ethereal reveals that, because of their own failure to improve their own race further, they have been testing and experimenting on other species throughout the universe in an attempt to identify a race worthy of being "Uplifted", searching for a race that is strong in both mind and body; the various species of alien troops that the player has encountered have all been failures in the Ethereals' experiments. By allowing humans to obtain their technology a few steps at a time, the Ethereals allowed humans to evolve to a fuller potential, and believe that humanity may be the culmination of their search, to find the perfect species to move on and prepare for "what lies ahead", a vaguely worded destiny that they do not describe further.


title: XCOM: Enemy Unknown

text: After slaying the Uber Ethereal, the Temple Ship begins to collapse into itself, creating a black hole, which would destroy the Earth due to its close proximity. While the psionically gifted Volunteer urges the other XCOM soldiers to rush back to their transport and escape the doomed ship, the Volunteer stays behind, using the psychic gift to take control of the ship and fly it further away from the planet, finally causing it to self-destruct and save Earth.


title: XCOM: Enemy Unknown

text: "XCOM: Enemy Unknown" went into development in early 2008 as a "very, very big budget" project with about 50–60 team members led by Jake Solomon. Its prototype was a straightforward remake of the original 1994 game "" with all the classic gameplay features. The game subsequently went through many revisions, and features were added, tested or removed to create the final result.


title: XCOM: Enemy Unknown

text: "XCOM: Enemy Unknown" was developed independently of 2K Marin's "XCOM" (later rebranded as ""), and although the two games are set in different universes, the developers of the two games were in contact with one another. "Enemy Unknown" was the first title developed by Firaxis Games not to feature the name of Sid Meier, who served as the director of creative development but was not directly involved in the game's development day to day. The designers made an internal board game to help get the "feel" of the game right.


title: XCOM: Enemy Unknown

text: The interface team was split into halves to develop separate GUIs for the PC and console releases. All members of the development team played and finished the original "Enemy Unknown" game – they were required to do so if they had not already when they joined the team. Roland Rizzo, who has been working with the "X-COM" series since the beginning, became the audio lead for the game and was tasked with reimagining and updating John Broomhall's famous original music score. Michael McCann, composer for "", was involved in creating the game's musical score. The "Civilization" series' art director Greg Foertsch was given the task of reimagining the look of "X-COM", including redesigning the classic alien species. The aim was to have the characters resemble action figures, and the result was a stylized, bright, flat-textured look.


title: XCOM: Enemy Unknown

text: "XCOM: Enemy Unknown" was revealed on January 5, 2012 by "Game Informer". A playable demo of the game was available at Electronic Entertainment Expo (E3) in June 2012. Pre-order bonuses included the "Classic X-COM Soldier" (a haircut for the player's male soldier based on the model for troops in the original 1994 X-COM) and the option to customize the aesthetic design of soldiers' armor. Those pre-ordering the PC version on Steam also received bonus items for Valve's "Team Fortress 2" and a free copy of Firaxis' 2010 strategy game "Civilization V". The game's playable demo version was released on September 24, 2012 for Steam, on October 9 for Xbox Live and on October 10 for PlayStation Network.


title: XCOM: Enemy Unknown

text: Eight custom promotional "XCOM: Enemy Unknown" arcade cabinets were produced in August 2011 by 2K Games and Bespoke Arcades. The machines were used to run tournaments of the game at various exhibitions including i47, London MCM Expo, Play Expo and Eurogamer Expo with the machines being awarded as prizes.


title: XCOM: Enemy Unknown

text: "XCOM: Enemy Unknown" was released in stores on October 9, 2012 for North American consumers and on October 12, 2012 for Australian and European consumers. The game was released for digital distribution via Steam on October 9, 2012. On PC, two editions were released: a normal edition and a special edition which includes a variety of unique items, including an art book, a fold-out poster of the XCOM headquarters, an XCOM insignia patch, and a collection of digital bonus assets such as desktop wallpapers, soundtrack and more.


title: XCOM: Enemy Unknown

text: An "Elite Edition", containing all previously released DLC, was announced for Mac OS X by Feral Interactive on February 26, 2013 and was released on April 25, 2013. An iOS port, scheduled to be released in the summer of 2013, was announced during a PAX East panel on March 23, 2013. A version for Android was released on April 2014.


title: XCOM: Enemy Unknown

text: An expansion pack, "XCOM: Enemy Within" was released worldwide on Steam and in retail stores on November 15, 2013. The pack retains the core storyline but adds a broad variety of content, including new weapons, special missions and the ability to enhance soldiers via genetic engineering or cybernetic implants. Both of those options consume an elusive substance called "Meld" that can be obtained during battles.


title: XCOM: Enemy Unknown

text: "XCOM: Enemy Unknown" greatly impressed the public and media at E3 2012, where it won a number of awards from a variety of gaming publications, such as the title of "Best Strategy Game" from GameSpy, "Game Informer", IGN, and Machinima. The game also won the titles "Best PC Game" and "Best Strategy Game" in the 2012 E3 Game Critics Awards.


title: XCOM: Enemy Unknown

text: A pre-release version of "XCOM: Enemy Unknown" received highly positive previews by, among others, "PlayStation Official Magazine", "Official Xbox Magazine" and Rock, Paper, Shotgun. The full version of the game also received a high praise from critics. Adam Biessener of "Game Informer" called it "a singular achievement that every gamer deserves to experience." Ian Dransfield of "Play" called the game "a phenomenal reimagining of a classic title and an instant classic in its own right." It was described as "a hallmark of excellence" by Destructoid and "an exemplary turn-based strategy game" by Joystiq.


title: XCOM: Enemy Unknown

text: Dan Stapleton of GameSpy wrote: "I consider the 1994 turn-based tactical masterpiece "X-COM: UFO Defense" to be the single best videogame ever made. Compared directly to that impossibly high standard, Firaxis' 2012 remake, "XCOM: Enemy Unknown", does remarkably well." "GamesTM" called it "a worthy reboot of the franchise, easily the most addictive game this year, and one of our favourite Firaxis games ever," with the final verdict of it being "fresh, yet authentic – a stunning reboot." Josh Harmon of "Electronic Gaming Monthly" ("EGM") stated that "to say that "XCOM: Enemy Unknown" is a phenomenal remake would be selling Firaxis' monumental accomplishment short. The developer hasn't just managed to capture the spirit of the original; they've also tweaked, trimmed, and innovated enough to deliver the freshest, most engaging strategy game in recent memory, if not ever."


title: XCOM: Enemy Unknown

text: Eurogamer's review by Rich Stanton described "XCOM: Enemy Unknown" as "a winner" and "a fantastic game" that "brings back and revitalises a classic." Alex Rubens of G4 called it "an exceptionally solid return for the series, and one that every turn-based tactics fan should experience," adding that "even if you never played the original, "XCOM: Enemy Unknown" is turn-based tactics and management at its finest, and a perfect introduction to the genre."


title: XCOM: Enemy Unknown

text: David Houghton of Game Revolution said that despite its flaws, the game "feels like the revival of not just a brand, but a genre." Polygon's Russ Pitts criticized the "weird dichotomy" of the game's strategy component, but praised the tactical gameplay, calling it "one of the best and most artfully designed strategy games in recent memory." Edwin Evans-Thirlwell of "Official Xbox Magazine" stated that it "isn't just Xbox 360's finest strategy experience – it's also a strategy game which changes how you think about strategy games."


title: XCOM: Enemy Unknown

text: The game's difficulty received both praise and concern. G4's review noted that "the extreme difficulty of the game might not be welcomed by all players" and "Official Xbox Magazine" described the game as "reliably unforgiving". According to "EGM", ""XCOM" hates you. "XCOM" wants you dead. And "XCOM" will see you dead, over and over again." "Game Informer" called it "one of the most challenging, intense gaming experiences of this generation." "Play"s review stated, "dying is back in fashion."


title: XCOM: Enemy Unknown

text: Several reviews commented on how addictive the game can be for the player. David Houghton of "PlayStation Official Magazine" called "XCOM" "one of the most unique and endlessly compulsive games of the year so far." Erik Kain of "Forbes" called it "one of the most addictive games I've ever played" that "falls somewhere between chocolate and crack on the scale of addictive substances." Allistair Pinsof of Destructoid, in pointing out how easily one could be absorbed in the game, told readers to "take the act of me wiping "XCOM" from my hard drive as high praise. It speaks volumes on how addictive and replayable "XCOM" is."


title: XCOM: Enemy Unknown

text: In a retrospective article about the original from 1994, Alec Meer of Eurogamer compared both games, coming to conclusion that ""X-COM" and "XCOM" are completely different games, both ingenious and both flawed in their own ways." According to Chris Schilling of VideoGamer.com, ""Enemy Unknown" is respectful of Julian Gollop's 1994 turn-based strategy classic, but it's not reverential." Charlie Hall of Ars Technica wrote that "in the end, this is not the "X-COM" that everyone was expecting. It's more. It's better. If you're merely looking for a highly competent re-skin of the original "X-COM", keep your eyes peeled for the upcoming "Xenonauts"." Gollop himself said:


title: XCOM: Enemy Unknown

text: Multiple publications including Giant Bomb, Kotaku, MTV and GameTrailers gave "XCOM: Enemy Unknown" their overall Game of the Year award for 2012. GameSpy also gave "XCOM" its Game of the Year award ("Achievements: Game of the Year, High Tension, Making Turn-Based Cool Again"), commenting that "few games can deliver the thrill of victory and the agony of defeat in the way that "XCOM" does."


title: XCOM: Enemy Unknown

text: "XCOM: Enemy Unknown" was chosen by the 2012 Spike TV Video Game Awards as a nominee in the category Best PC Game. At the 16th Annual D.I.C.E. Awards, it was nominated for three awards, including "Game of the Year", and ended up winning two for 2012's "Strategy/Simulation Game of the Year" and "Outstanding Achievement in Gameplay Engineering". Awarding the game its title of Strategy Game of the Year, "PC Gamer" wrote it can be "forging player memories that'll live as long as you play and care about games."


title: XCOM: Enemy Unknown

text: A sequel to "XCOM: Enemy Unknown", "XCOM 2", was released on February 5, 2016. It was developed by Firaxis Games and was released on Microsoft Windows, OS X and Linux. The game takes place 20 years after the events of Enemy Unknown, in an alternate scenario where XCOM failed to stop the alien invasion and humanity surrenders. The player controls a small resistance movement fighting against the alien conquerors.


title: Robert Evans (journalist)

text: Robert Evans is an American author, journalist, and podcast host who has reported on global conflicts and online extremism. A former editor at the humor website Cracked.com, Evans now writes for the investigative journalism outlet Bellingcat while working on several podcasts, including "Behind the Bastards", "Behind the Police", "Behind the Insurrections", "It Could Happen Here", "The Women's War", and "Worst Year Ever". In 2021 he published his first novel, "After The Revolution," in a serialized podcast.


title: Robert Evans (journalist)

text: Evans worked at the humor website "Cracked" as an editorial manager. In that position, Evans led a team that published "personal experience" articles. These articles fell into two main categories: journalistic pieces involving a variety of sources and personal narratives.


title: Robert Evans (journalist)

text: In 2016 Evans published his first book, "A Brief History of Vice," about the formative effects of narcotics on the development and history of civilization.


title: Robert Evans (journalist)

text: He has reported on conflicts in Iraq, Ukraine, and Rojava, as well as on far-right extremists in the United States.


title: Robert Evans (journalist)

text: In the late 2010s and early 2020s, Evans produced a variety of content about 8chan, an anonymous message board, as well as the Gamergate controversy movement, a movement he describes as largely organically generated, with some direction given by white supremacists and extremists with long experience in radicalizing people on internet forums.


title: Robert Evans (journalist)

text: Following the March 2019 Christchurch mosque shootings, news outlets including "Rolling Stone", "Vox", and "The Atlantic" referenced Evans' warning about the nature of the shooter's manifesto. Evans argued that the manifesto was merely a red herring, full of references and memes meant to distract observers. Following the 2019 Poway synagogue shooting, "Vox" relied on Evans' work to explain how the shooter's manifesto again constituted a 74-page in-joke meant to further radicalize other 4chan /pol/ users.


title: Robert Evans (journalist)

text: In a 2020 "Bellingcat" article, Evans discussed the emergence and qualities of the boogaloo movement, a loose-knit group of individuals who express interest in fomenting American civil unrest. Evans says that he became aware of the boogaloo movement when he observed members at 2020 Virginia Citizens Defence League Lobby Day.


title: Robert Evans (journalist)

text: Starting in late May 2020, Evans covered the George Floyd protests in Portland, Oregon. He began reporting in the first days of the protests by taking footage of protesters, counter-protesters, and police. His reporting on the protests was highlighted in the "New York Times" opinion section, which published an interview with Evans after the 50th day of protests about covering the events.


title: Robert Evans (journalist)

text: In July, Evans joined a class-action lawsuit against the City of Portland for police use of force at the protests. The suit is non-monetary, seeking instead "declaratory and injunctive relief — asking the court to find the plaintiffs within their rights and to order police to stop brutalizing and unlawfully arresting protesters." Evans joined freelance journalist Bea Lake and housing services specialist Sadie Oliver-Grey as a plaintiff. The suit alleges that police officers were unlawfully violent, stopped journalists from reporting, and interfered with the right to free speech. The suit describes incidents that occurred to Evans including the "police allegedly threatening him with arrest if he did not leave the area, shooting him in the foot with a tear gas grenade and spraying him, and repeatedly shoving him".


title: Robert Evans (journalist)

text: On Saturday, August 22, a right-wing protester wielding a baton broke Evans' hand while he was filming. In an interview with "The Guardian", Evans said the right-wing counter-protesters "absolutely came prepared to fight", were "very aggressive from the jump", and were equipped with "knives, guns, paintball guns with frozen pellets, batons".


title: Robert Evans (journalist)

text: In August, the song "No Cock Like Horse Cock" became a popular protest song in the Pacific Northwest. It was unclear exactly how it became popularized, but Pepper Coyote, the artist who produced the song, surmised that protesters became aware of his work through a cover song that appeared on Evans' "Behind the Bastards".


title: Robert Evans (journalist)

text: Evans is the host of the podcast "Behind the Bastards" and one of three co-hosts of the podcast "Worst Year Ever".


title: Robert Evans (journalist)

text: In 2019, Evans completed the podcast series "The War on Everyone", a podcast about how white supremacy and fascism have developed and spread into the American consciousness in the modern age, as well as "It Could Happen Here", a podcast about the possibility of a Second American Civil War.


title: Robert Evans (journalist)

text: Evans published a new podcast series titled "The Women's War" in March and April 2020 about the primarily Kurdish autonomous region in Syria known as Rojava.


title: Robert Evans (journalist)

text: Evans also published a "Behind the Bastards" podcast miniseries titled "Behind the Police" in June and July 2020, covering the history of policing in the United States to inform the present time of civil unrest.


title: Robert Evans (journalist)

text: Behind the Police was cohosted by Jason Petty. In November 2020 through early 2021, Evans published "Uprising: A Guide From Portland", a podcast detailing first-hand accounts of the 2020 George Floyd protests in Portland, Oregon.


title: Robert Evans (journalist)

text: In August 2021, iHeartMedia announced a launch of a new podcast network "Cool Zone Media" helmed by Evans, who would become its head of content. The network would unite under one umbrella both existing and upcoming podcasts from Evans and his frequent collaborators such as Jake Hanrahan and Jason "Propaganda" Petty.


title: Pershing II

text: The Pershing II Weapon System was a solid-fueled two-stage medium-range ballistic missile designed and built by Martin Marietta to replace the Pershing 1a Field Artillery Missile System as the United States Army's primary nuclear-capable theater-level weapon. The U.S. Army replaced the Pershing 1a with the Pershing II Weapon System in 1983, while the German Air Force retained Pershing 1a until all Pershings were eliminated in 1991. The U.S. Army Missile Command (MICOM) managed the development and improvements, while the Field Artillery Branch deployed the systems and developed tactical doctrine.


title: Pershing II

text: Development began in 1973 for an updated Pershing. The Pershing 1a had a 400 kt warhead, which was greatly over-powered for the Quick Reaction Alert (QRA) tactical role the weapon system filled. Reducing warhead yield, however, required a significant increase in accuracy to match Pershing 1a's ability to kill hard targets like command bunkers. The contract went to Martin Marietta in 1975 with the first development launches in 1977. Pershing II was to use the new W85 warhead with a 5 to 80 kt variable yield or an earth-penetrator W86 warhead. The warhead was packaged in a maneuverable reentry vehicle (MARV) with active radar guidance and would use the existing rocket motors. Requests from Israel to buy the new Pershing II were rejected in 1975.


title: Pershing II

text: The Soviet Union began deployment of the RSD-10 Pioneer (NATO designation SS-20 Saber) in 1976. Since the first version of the RSD-10 had a range of and two warheads, the Pershing II requirement was changed to increase the range to , giving the ability to reach targets in eastern Ukraine, Belarus or Lithuania. The NATO Double-Track Decision was made to deploy both the medium-range Pershing and the longer-range, but slower BGM-109G Ground Launched Cruise Missile (GLCM) to strike potential targets farther to the east. The Pershing II with the longer-range motors was initially referred to as Pershing II Extended Range (PIIXR), then reverting to Pershing II.


title: Pershing II

text: Both the hard-target capability and W86 nuclear warhead were canceled in 1980, and all production Pershing II missiles carried the W85. A concept warhead using kinetic energy penetrators for counter-airfield operations never materialized.


title: Pershing II

text: Because of SALT II agreements, no new launchers could be built, therefore the Pershing 1a M790 launchers were modified into the Pershing II M1003 launchers. The functions of the vehicle-mounted programmer test station needed for the older systems were consolidated into the Launch Control Assembly (LCA) in the Ground Integrated Electronics Unit (GIEU) on the side of the launcher. The warhead and radar sections were carried as an assembly on a pallet that rotated to mate with the main missile.


title: Pershing II

text: There were two prime movers for the launcher, both with a crane used for missile assembly and a generator to provide power for the launcher and missile. The U.S units used the M983 HEMTT with a Hiab 8001 crane and a 30 kW generator. Tactical units in Germany used the M1001 MAN tractor with an Atlas Maschinen GmbH AK4300 M5 crane and a 30 kW generator. Since the new guidance system was self-orienting, the launcher could be emplaced on any surveyed site and the missile launched within minutes.


title: Pershing II

text: The new rocket motors were built by Hercules: To minimize airframe weight, the rocket cases were spun from Kevlar with aluminum attachment rings. The Pershing 1a cable mast was replaced by a conduit attached to each motor containing two cables: Cables internally connected from motor to motor and to the G&C: The aft end of the first stage had two tail plugs that connected to the GIEU.


title: Pershing II

text: The reentry vehicle (RV) was structurally and functionally divided into three sections: the radar section (RS), the warhead section (WHS), and the guidance and control/adapter (G&C/A) section.


title: Pershing II

text: The guidance and control/adapter (G&C/A) section consisted of two separate portions, the G&C and the adapter connected by a manufactured splice. At the forward end of the G&C there was a quick access splice for attachment to the warhead section. At the aft end, the adapter was grooved to accept the V-band that spliced the propulsion section to the G&C section. The RV separation system consisted of a linear shaped charge ring assembly bolted to the G&C section so that separation occurred just forward of the G&C manufactured splice. A protective collar on the outer surface of the adapter, mounted over the linear shaped charge, provided personnel protection during G&C/A handling operations.


title: Pershing II

text: The G&C portion contained two guidance systems. The Singer-Kearfott inertial navigation system that provided guidance through the terminal phase. The primary terminal guidance system was a Goodyear Aerospace active radar guidance system. Using radar maps of the target area, the Pershing II had an accuracy of circular error probable. If the radar guidance failed, the inertial guidance would keep the missile on-target with a lower accuracy. The G&C also contained the Pershing Airborne Computer (PAC), the digital correlator unit (DCU) and actuators to drive the air fins.


title: Pershing II

text: The warhead section contained the W85 warhead, the rate gyro unit and the cables that passed from the G&C section to the RS.


title: Pershing II

text: The radar section consisted of the Goodyear radar unit with the antenna enclosed in an ablative radome. The radar unit transmitted radio waves to the target area during the terminal phase, received altitude and video information and sent the detected video and altitude data to the data correlator unit (DCU) in the G&C section.


title: Pershing II

text: The highly accurate terminal guidance technique used by the Pershing II RV was radar area correlation, using a Goodyear Aerospace active radar homing system. This technique compared live radar video return to pre-stored reference scenes of the target area and determined RV position errors with respect to its trajectory and target location. These position errors updated the inertial guidance system, which in turn sent commands to the vane control system to guide the RV to the target.


title: Pershing II

text: At a predetermined altitude, the radar unit activated to provide altitude update data and begin scanning the target area. The analog radar video return was digitized into two-bit pixels by the correlator unit and was formatted into a 128 by 128 array. The target reference scene data, loaded prior to launch via the ground and missile data links, were also encoded as two-bit pixels and placed in reference memory formatted in a 256 by 256 array. The reference scene resolution necessary to correspond to the decreasing altitude of the RV was effected by placing four reference data arrays in memory, each representing a given altitude band. This correlation process was performed several times during each of four altitude bands and continued to update the inertial guidance system until just before the impact.


title: Pershing II

text: If for some reason the correlator system failed to operate or if the correlation data quality was faulty the inertial guidance system continued to operate and guided the RV to the target area with inertial accuracy only.


title: Pershing II

text: Goodyear also developed the Reference Scene Generation Facility, a truck-mounted shelter containing the equipment required to program the missile targeting controlled by a DEC PDP-11/70. Radar maps of target areas were stored on disk, then specific targeting data was transferred to a quarter-inch cartridge in a hardened carrier. During countdown operations, the cartridge was plugged into the launcher control panel to program the missile with targeting data.


title: Pershing II

text: Prior to launch, the missile was referenced in azimuth by its gyrocompass inertial platform. After launch, the missile followed an inertially guided trajectory until RV separation. Attitude and guidance commands during powered flight (except for roll attitude) were executed via the swivel nozzles in the two propulsion sections. Roll control was provided by two movable air vanes on the first stage during first stage flight and by the RV air vanes during second stage flight. The first stage also had two fixed air vanes for stability during first stage powered flight.


title: Pershing II

text: The midcourse phase of the trajectory was initiated at RV separation and continued until the terminal phase began. At the beginning of the midcourse phase, the RV was pitched down to orient it for reentry and to reduce its radar cross-section. The midcourse attitude was then controlled by the RV vane control system during atmospheric exit and reentry, and by a reaction control system during exoatmospheric flight.


title: Pershing II

text: At a predetermined altitude above the target, the terminal phase would begin. A velocity control maneuver (pull up, pull down) was executed under inertial guidance control to slow down the RV and achieve the proper impact velocity. The radar correlator system was activated and the radar scanned the target area. Radar return data was compared to pre-stored reference data and the resulting position fix information was used to update the inertial guidance system and generate RV steering commands. The RV was then maneuvered to the target by the RV vane control system.


title: Pershing II

text: Soviet estimates put the system's range at and they also believed that the missile was armed with an earth-penetrating warhead. These two errors contributed to Soviet fears of the weapon, believing it could be used to decapitate the Soviet Union. In reality, from positions in West Germany the system could not target Moscow.


title: Pershing II

text: On 12 December 1979, the military commander of NATO decided to deploy 572 new nuclear missiles in Western Europe: 108 Pershing II Missiles and 464 Ground Launched Cruise Missiles. Of the cruise missiles, 160 were to be placed in England, 96 in West Germany, 112 in Italy (in Sicily), 48 in the Netherlands, and 48 in Belgium. All 108 Pershing II missiles were to be emplaced in West Germany replacing the current Pershing 1a missiles. The German Air Force planned to replace their 72 Pershing 1a missiles with the short-range Pershing 1b, but this never happened.


title: Pershing II

text: The second significant aspect of the NATO decision was the readiness to trade with the Soviet Union for the reduction or total elimination of these missiles against similar reductions or elimination of the Soviet SS-20 missiles. NATO's condition for not carrying out its plans for missile deployment would be the willingness of the U.S.S.R. to halt the deployment of the mobile SS-20 missiles that could be aimed at Western Europe and to remove the SS-20s that had already been deployed. In 1979, when the decision to deploy new NATO nuclear missiles was made, the Warsaw Pact had fourteen SS-20 launch sites selected, with one operational. According to estimates by NATO, at the beginning of 1986, the Warsaw Pact had deployed 279 SS-20 mobile missile launchers with a total of 837 nuclear warheads based in the eastern U.S.S.R.


title: Pershing II

text: The first Pershing II missiles were deployed in West Germany beginning in late November 1983 and completed in late 1985 with a total of 108 launchers. Initial Operational Status (IOS) was achieved on 15 December 1983 when A Battery, 1st Battalion, 41st Field Artillery Regiment rotated onto operational status with the Pershing II at its site in Mutlangen. By 1986 all three missile battalions were deployed with 108 Pershing II missiles, stationed in West Germany at Neu-Ulm, Mutlangen and Neckarsulm.


title: Pershing II

text: The deployment of Pershing II and GLCM missiles was a cause of significant protests in Europe and the US, many organized by the Campaign for Nuclear Disarmament.


title: Pershing II

text: Protests against the short-range MGM-52 Lance nuclear missile began in July 1981 in Engstingen, West Germany. In October 1981, 300,000 protesters assembled in Bonn. European Nuclear Disarmament began a campaign for nuclear disarmament in 1982. The Seneca Women's Encampment for a Future of Peace and Justice was formed in 1983 to protest the deployment. In 1983, protesters went to court to stop the Pershing II deployment as a violation of Article 26(1) of the Basic Law for the Federal Republic of Germany, which prohibited West Germany from preparing for an offensive war. The Federal Constitutional Court rejected these claims. Again in Bonn in October 1983, as many as 500,000 people protested the deployment and a human chain was formed from the US Army headquarters in Stuttgart to the gates of Wiley Barracks in Neu-Ulm, the site of one of the Pershing battalions. Due to accessibility, the protests focused on the Mutlangen Missile Storage Area from Easter 1983 until the signing of the Intermediate-Range Nuclear Forces Treaty in 1987. The 56th Field Artillery Command worked closely with the local police to ensure that the protesters interacted peacefully with the U.S. soldiers.


title: Pershing II

text: The Plowshares movement was active in actions against the deployment. 14 July 1983, Plowshare activists entered the Avco plant in Wilmington, Massachusetts and damaged equipment related to Pershing II and MX missiles. On 4 December 1983, four Plowshare activists cut through a fence in Schwäbisch Gmünd and damaged a truck. On 22 April 1984, eight Plowshare activists associated entered the Martin Marietta Aerospace plant in Orlando, Florida where they damaged Pershing II components and a Patriot missile launcher and poured containers of their own blood on equipment. Four Plowshare activists entered the missile storage area (MSA) at Schwäbisch Gmünd, West Germany on 12 December 1986 and damaged the tractor of a Pershing II erector launcher and hung a banner over the truck.


title: Pershing II

text: On 24 September 1984, elements of 1st Battalion, 41st Field Artillery were on a field exercise near Mutlangen. A launcher and MAN tractor were parked on the edge of a dirt road when it slid off and rolled over into deep snow. The equipment was recovered after a six-hour operation.


title: Pershing II

text: On 11 January 1985, three soldiers of C Battery, 3rd Battalion, 84th Field Artillery Regiment were killed in an explosion at Camp Redleg, the CAS site near Heilbronn. The explosion occurred while removing a missile stage from the storage container during an assembly operation. An investigation revealed that the Kevlar rocket bottle had accumulated a triboelectric charge in the cold dry weather; as the motor was removed from the container, the electrical charge began to flow and created a hot spot that ignited the propellant. A moratorium on missile movement was enacted through late 1986, when new grounding and handling procedures were put into place. Ballistic covers were later added to the Pershing II missiles and to the Pershing 1a missiles still in use by the German Air Force.


title: Pershing II

text: The incident gave the protesters a new issue: safety. The 56th Field Artillery Command worked closely with local authorities, the press and representatives of the protest groups to keep them informed.


title: Pershing II

text: Pershing 1b was a single-stage, reduced-range version of Pershing II with the same range as the Pershing 1a. The Pershing II launcher was designed so that the cradle could be easily repositioned to handle the shorter missile airframe. The intent was to replace the German Air Force's Pershing 1a systems with Pershing 1b, since SALT II limited the range of German-owned missiles. The German government agreed to destroy its Pershing 1a systems when the U.S. and the U.S.S.R. signed the INF Treaty, thus the Pershing 1b was never deployed. The single-stage missile was used for launches from White Sands Missile Range due to range limitations.


title: Pershing II

text: Pershing II Reduced Range (RR) was a follow-on concept that would have modified the launchers to hold two single-stage missiles.


title: Pershing II

text: Pershing III was a proposal for a four-stage version that would have replaced the LGM-118 Peacekeeper.


title: Pershing II

text: Pershing III is also a proposal for a coast-based missile system to counter the Chinese DF-21D anti-ship ballistic missile.


title: Pershing II

text: The Pershing systems were eliminated after the ratification of the Intermediate-Range Nuclear Forces Treaty on 27 May 1988. The missiles began to be withdrawn in October 1988 and the last of the missiles were destroyed by the static burn of their motors and subsequently crushed in May 1991 at the Longhorn Army Ammunition Plant near Caddo Lake, Texas. Although not covered by the treaty, West Germany agreed unilaterally to the removal of the Pershing 1a missiles from its inventory in 1991, and the missiles were destroyed in the United States.


title: Pershing II

text: The INF treaty only covered the destruction of the launchers and rocket motors. The W-85 warheads used in the Pershing II missiles were removed, modified, and reused in the B61 nuclear bomb.


title: Pershing II

text: The Orbital Sciences Storm I target missile used air vanes from the Pershing 1a. The Pershing II guidance section was re-used in the Coleman Aerospace Hera and the Orbital Sciences Corporation Storm II target missiles.


title: Pershing II

text: The INF Treaty allowed for seven inert Pershing II missiles to be retained for display purposes. One is now on display in the Smithsonian Institution's National Air and Space Museum in Washington, D.C., alongside a Soviet SS-20 missile. Another is at the Central Armed Forces Museum in Moscow, Russia, also with an SS-20. A number of inert Pershing 1 and Pershing 1a missiles are displayed in the U.S. and Germany.


title: Pershing II

text: Scrap material from the Pershing II and SS-20 missiles was used in several projects. Zurab Tsereteli created a sculpture called "Good Defeats Evil", a , monumental bronze statue of Saint George fighting the dragon of nuclear war, with the dragon being made from sections of the Pershing II and SS-20 missiles. The sculpture was donated to the United Nations by the Soviet Union in 1990 and is located on the grounds of the United Nations Headquarters in New York City.


title: Pershing II

text: In 1991, Leonard Cheshire's World Memorial Fund for Disaster Relief sold badges of the group logo made of scrap material. The Parker Pen Company created a series of pens with a Memorial Fund badge made of scrap missile material, with half the proceeds going to the fund.


title: Pershing II

text: On 4 November 1991 the Ronald Reagan Presidential Library opened in Simi Valley, California. The then five living presidents, Richard Nixon, Gerald Ford, George Bush, Jimmy Carter and Ronald Reagan were present at the opening. Parker presented them each with a black ballpoint Duofold Centennial with the Presidential seal on the crown formed from scrap Pershing and SS-20 material, and engraved signatures of the presidents. The pen was also offered in a walnut box also with the names of all five presidents and the Presidential seal.


title: Pershing II

text: In 2000, a number of U.S. Army Pershing missile veterans decided to seek out their fellow veterans and to start acquiring information and artifacts on the Pershing systems. In 2004, the Pershing Professionals Association was incorporated to meet the long-term goals—to preserve, interpret and encourage interest in the history of the Pershing missile systems and the soldiers who served, and to make such information accessible to present and future generations to foster a deeper appreciation of the role that Pershing played in world history.


title: Pershing II

text: Veterans of the 2nd Battalion, 4th Infantry Regiment, who had performed the security for the Pershing systems formed a subchapter known as the Pershing Tower Rats. The two German Air Force missile squadrons also formed veterans groups known as the Flugkörpergeschwader 1 eV.


title: Eyeshield 21

text: The manga was originally serialized in Shueisha's "Weekly Shōnen Jump" from July 2002 to June 2009. The series consists of 333 chapters collected in 37 "tankōbon" volumes. An anime adaptation consisting of 145 television episodes was co-produced by TV Tokyo, NAS, and Gallop. The television series first aired on Japan's TV Tokyo network from April 2005 to March 2008. The "Eyeshield 21" franchise has spawned two original video animations (OVAs), audio albums, video games, and other merchandise.


title: Eyeshield 21

text: In North America, the manga was released by Viz Media from April 2005 to October 2011. The anime series was later licensed in North America by Toonami Jetstream as a joint effort with Viz Media and aired in December 2007, on its site, but before its completion, the streaming service was shut down. The whole series was streamed in English by Crunchyroll, while Sentai Filmworks licensed the series, with distribution from Section23 Films on DVDs.


title: Eyeshield 21

text: In Japan, the "Eyeshield 21" manga has sold over 20 million volumes. The manga and anime have been featured at various times in weekly top ten lists of best-selling in their respective media. The anime has been watched by a large number of television viewers in Japan, helping to raise American football's popularity in the country. Publications for manga, anime, and others have commented on "Eyeshield 21", which received positive comments for its artwork and characters, and negative responses to its non-football scenes.


title: Eyeshield 21

text: In Tokyo, a weak, unassertive boy named Sena Kobayakawa enters the Deimon Private Senior High School. Sena's only remarkable physical abilities are his running speed and agility, which are noted by the school's American football team captain Yoichi Hiruma. Hiruma forces Sena to join the Deimon Devil Bats as its running back. To protect his identity from other teams who want to recruit him, Sena is forced to publicly assume the role of the team secretary and enter the field under the pseudonym of "Eyeshield 21" wearing a helmet with an eyeshield to hide his features. The makeshift team initially takes part in the spring football tournament hoping to win through the strength of their new "secret weapon". However, the extremely weak team is eliminated early by the Ojo White Knights, one of the best football teams in Japan.


title: Eyeshield 21

text: After Deimon's defeat, the spring tournament is revealed as secondary in importance to the fall tournament, where the teams compete for the chance to play in the Christmas Bowlthe high school football league championship. Hiruma, Sena, and Ryokan Kurita regroup and slowly build a real team from misfits and students looking to define themselves, such as Tarō "Monta" Raimona baseball player who can only catchand the bullies collectivelly known as Ha-Ha Brothers. Other characters slowly join the team, and the series follows the building and growth of the Deimon Devil Bats and its members, and rival teams as they all strive to achieve their goal of playing in the Christmas Bowl.


title: Eyeshield 21

text: Some time after the Deimon Devil Bats win the Christmas Bowl and they become the best team in the country, Japan begins to gather the best football players to form a team to represent it at the American Football Youth World Championship, where a Most Valuable Player (MVP) will be awarded an NFL contract and $3 million. Team Japan reaches the final against Team America, in which the game ends as a tie, and both teams are declared winners. Both teams are unsatisfied with this and return to the field for their own, improvised "overtime", causing chaos with officials. It is unclear which team wins the unofficial extra period, but Panther of Team America holds the MVP trophy aloft, winning the professional contract with the San Antonio Armadillos.


title: Eyeshield 21

text: The series concludes with Sena becoming the captain of the Devil Bats after Hiruma and Kurita leave school to attend college. In his final year of high school, Sena is invited to Notre Dame High School. In the final chapter, the main characters are in college or playing amateur-league football while employed.


title: Eyeshield 21

text: Before the series was published regularly, Riichiro Inagaki and Yusuke Murata published two one-shots called and on March 5 and 12, 2002 in "Weekly Shōnen Jump". When it would become a serial, the editorial department asked if Inagaki wanted to both write and draw the series, but Inagaki felt he was "so rookie", so he asked Murata to be the illustrator. Before being asked to work on "Eyeshield 21", Murata had read some of Inagaki's manga and noted that they "had many cool design concepts of uniforms and equipment". He said, "it could be turned into a great manga story" and he would "be happy to take the challenge"; eventually he was chosen.


title: Eyeshield 21

text: During "Eyeshield 21" original run in the magazine, Inagaki went to the United States to see college football matches, and National Football League games. Despite having never played American football, Inagaki chose this theme after deciding that he wanted to create "a protagonist that was wimpy at the beginning, yet could perform outstandingly in a sports game", and with this premise in mind he decided that American football would be "a very suitable material." When originally creating "Eyeshield 21", Inagaki said he was wary because he did not want his manga becoming "a simulator of football". The fact that football is not a popular sport in Japan also worried Inagaki. As last resort, he thought to turn the series into a ""Kamen Rider"-style masked hero story" if it could not met the popularity required for the magazine. However, it was such a popular series that online commentators said that, considering the series' final length, the editors may have insisted that "Eyeshield" be kept going due to business reasons. However, Inagaki declared that the manga was "exactly how [he] wanted to tell the story" and that Murata also seconded it.


title: Eyeshield 21

text: The "Eyeshield 21" manga series was written by Riichiro Inagaki, illustrated by Yusuke Murata, and originally serialized by Shueisha in the "shōnen" manga magazine "Weekly Shōnen Jump" from July 23, 2002, to June 15, 2009. The manga consists of 333 chapters spanning 37 "tankōbon" (collected volumes), released from December 20, 2002, to October 2, 2010. "Eyeshield 21" has also been published as part of the "Shueisha Jump Remix" series of magazine-style books. Fourteen volumes were released between June 28, 2010, and February 14, 2011.


title: Eyeshield 21

text: An English translation of the manga was published in North America by Viz Media under the "Shonen Jump Advanced" label between April 5, 2005, and October 4, 2011.


title: Eyeshield 21

text: The manga has also been licensed in some countries such as in France by Glénat, in Hong Kong by Culturecom, in Indonesia by Elex Media Komputindo, in Italy by Panini Comics, in South Korea by Daewon Media, and in Taiwan by Tong Li Publishing.


title: Eyeshield 21

text: Two original video animations (OVA) based on the "Eyeshield 21" manga series were developed. The first one, named , was developed by Production I.G and shown as part of the Jump Festa Anime Tour in September 2003 and in Jump Festa 2004. The second OVA, titled , was shown at Jump Festa 2005. The two OVAs were later released on DVD; the first was released with the second OVA of "Naruto" in a compilation called "Jump Festa 2004 Super DVD". The other was released by Bandai Visual as an extra track on the sixth DVD of the "Eyeshield 21" anime series.


title: Eyeshield 21

text: The "Eyeshield 21" anime adaptation was co-produced by TV Tokyo, NAS, and Gallop, and was directed by Masayoshi Nishida until episode 103, and by Shin Katagai from 104 to 145. The series of 145 television episodes aired in Japan from April 6, 2005, to March 19, 2008, on TV Tokyo. In Japan, Bandai Visual distributed the anime in DVD format; thirty-six volumes were released between July 26, 2006, and June 26, 2007. Some changes were done in comparison to the manga; for example, swearings and guns or gambling references were reduced.


title: Eyeshield 21

text: Initially, Viz Media and Cartoon Network planned to air a dubbed version of "Eyeshield 21" on the internet video streaming service Toonami Jetstream, and on NFL Rush site as a joint effort with National Football League (NFL). The anime was eventually posted only on Toonami Jetstream, with the first episode, which condensed three episodes, being available on December 17, 2007. However, it was not completed due to Toonami Jetstream's cancellation and shutdown. In December 2008, the video streaming service Crunchyroll announced that it would begin to stream "Eyeshield 21" subtitled on its site on January 2, 2009. The last episode was available on November 1, 2009, for premium users, and on March 7, 2010, for free users. On February 26, 2010, Section23 Films announced that Sentai Filmworks received the license to the anime. The first fifty-two episodes were released on four subtitled-only DVDs between May 18, 2010, and February 8, 2011.


title: Eyeshield 21

text: The music for the "Eyeshield 21" anime adaptation was composed by Kō Ōtani. The series use twelve pieces of theme music, five opening and seven ending themes. The opening themes are "Breakthrough" and "Innocence" by V6, "Dang Dang" by ZZ, "Blaze Line" by Back-On, and by Short Leg Summer. The ending themes are "Be Free" by Ricken's, "Blaze Away" by The Trax, "Goal" by Beni Arashiro, "Run to Win" by Aya Hirano, Miyu Irino, Koichi Nagano and Kappei Yamaguchi, "A day dreaming..." by Back-On, "Flower" by Back-On, and "Song of Power" by Short Leg Summer.


title: Eyeshield 21

text: A number of audio CDs linked to the anime series have been released in Japan. The original soundtrack was released on two discs by Avex Mode on March 5, 2008, under the title "Eyeshield 21 Complete Best Album". Three compilation albums, "Eyeshield 21 Original Soundtrack Sound Field 1", "Eyeshield 21 Sound Field Especial", and "Eyeshield 21 Song Best", featuring opening and ending themes, insertion songs, and character and team songs were released on August 31, 2005, December 21, 2005, and March 23, 2006, respectively. Six maxi singles containing character songs have also been published. The first three, for Sena Kobayakawa, Mamori Anezaki, and Monta, were released on October 26, 2005. The other three, with the songs of Haruto Sakuraba, Seijurou Shin, and Suzuna Taki, were released on January 25, 2006. In addition to the musical CDs, "Eyeshield 21 Drama Field 1", an audio drama CD, was released by Avex on September 21, 2005.


title: Eyeshield 21

text: Konami produced "Eyeshield 21" games for Sony video game systems; it released for the PlayStation 2 on December 22, 2005, and for the PlayStation Portable on March 2, 2006. Nintendo secured the rights to the "Eyeshield 21" video game license for its systems in December 2004, releasing "Eyeshield 21: Max Devil Power" for the Nintendo DS on February 2, 2006, and "Eyeshield 21: Devilbats Devildays" for the Game Boy Advance on April 6, 2006. Another game was scheduled for release on the Nintendo GameCube, but it was later canceled. Nintendo published an "Eyeshield 21" game for the Wii, entitled , which was released in Japan on March 8, 2007. Two non-football games, "Jump Super Stars" and "Jump Ultimate Stars", released for the Nintendo DS, have featured characters from the series. Various Devil Bats, Shin and Sakuraba from the White Knights appear in support cameos.


title: Eyeshield 21

text: Two art books based on "Eyeshield 21" were released. The first, , was published on November 2, 2006. The second, entitled "Paint Jump: Art of Eyeshield 21", was released on December 19, 2008. , a databook, was published on October 4, 2005. A pair of light novels were launched; the first, written by Katsumi Hasegawa, based on and named for the first OVA, was published on March 24, 2004. The second, , written by Eijima Jun, was published on May 26, 2006. The only original creator of the series who worked on these light novels was Murata, who illustrated them.


title: Eyeshield 21

text: In Japan, jigsaw puzzles, action figures, plush dolls, calendars, key chains, and a medal game machine were sold as merchandise for the series. Konami also released a collectible card game series.


title: Eyeshield 21

text: The manga has sold more than 20 million copies in Japan; individual volumes frequently appeared on top ten lists of best-selling manga there ("see table"). Individual volumes have appeared in Diamond Comic Distributors's lists of 300 best-selling graphic novels in North America several times. In 2011, the Japanese website Ameba conducted a "Top 10" online web poll of the "Best "Shōnen Jump" Manga of the 21st Century" and "Eyeshield 21" was placed seventh, although in another poll of the best "Shōnen Jump" titles that the readers nonetheless did not want to continue reading, "Eyeshield 21" ranked twentieth. The anime adaptation was also featured several times in Japanese television rankings, with the first episode having a 7.5 percent television viewership rating. In 2006, Japanese television network TV Asahi conducted a poll for the top hundred anime, and "Eyeshield 21" was placed 47th. Moreover, "Eyeshield 21"s series is credited with increasing the number of Japanese teenagers playing American football. However, commenting on its genre lack of popularity in the United States, Jason Thompson wrote in Anime News Network that "Even "Eyeshield 21", a sports manga which is practically made for Americans, wasn't a big hit here."


title: Eyeshield 21

text: Critics have generally given the "Eyeshield 21" manga positive reviews. Deb Aoki from About.com wrote that tying with "Bleach", "Eyeshield 21" was the best continuing "shōnen" manga of 2007, because it "has well-written characters, dynamic artwork, nail-biting cliffhangers, plus a winning mix of comedy, action and drama". On the 2008 list, Aoki listed "Eyeshield 21" as the best continuing "shōnen", as it was able to "[come] into its own" from other "shōnen" series. In that same year, Pop Culture Shock's Sam Kusek elected it the best continuing manga series. Chris Zimmerman of Comic Book Bin was positive on his review of the volumes 30–33; he affirmed it is "one of the best shonen titles out there" and described it as "a superb series, with well developed characters, intense action, and touching humor." Scott Campbell of Active Anime commented it is an "action-filled" series with great artwork and humor, and that it "has managed to continually get more and more dynamic with each volume".


title: Eyeshield 21

text: Jarred Pine from Mania.com praised the humor and how the creators "bring out the energy and excitement of the game for the readers". June Shimonishi, reviewing for "School Library Journal", wrote that it "delivers a fresh and entertaining take on all the standard sports clichés". She also said that its art is "superb ... with every inch filled with details and no gag left unseen". Zac Bertschy from Anime News Network (ANN) declared "Eyeshield 21" "defies convention" by turning what most might consider "a really ridiculously bad idea" into "something most everyone would be able to enjoy". Carlo Santos from ANN called it a "typical sports story", writing that what make it an above average series are its characters and artwork. He also wrote that people who think American football is boring "may change their minds after seeing the action sequences in "Eyeshield 21"." Later, Santos said, "[a] lot of familiar clichés show themselves" in "Eyeshield 21", and that "[t]he storyline also does a sloppy job of keeping track of the game ... making it even less believable than it already is". However, overall, he considered the story has good art, action and pace, featuring "pure sports storytelling at its finest".


title: Eyeshield 21

text: The anime adaptation of "Eyeshield 21" received positive and mixed responses. Bobby Cooper from DVD Talk praised how the rules of American football are "explained to a foreign audience that has no clue what it's all about", adding that instructions at the commercial breaks "were informative and similar to the Go lessons of "Hikaru No Go"." He also said the explanations were "hilarious", but that ""Eyeshield 21" is an excellent introduction to football". The on-field action was also praised, with he saying the sports action is "where "Eyeshield" 21 truly shines", although he criticized the scenes away from the football field, "the pacing slows to a crawl and the storyline gets a little boring". In her review, Erin Finnegan from Anime News Network stated, "[t]he pace of "Eyeshield 21" is its saving grace. It's way less boring than all the time outs and commercial breaks in a regular NFL game. Football is hard to understand, but "Eyeshield 21" explains the Byzantine rules ... in an entertaining way. We're never left waiting for the ref's decision for long minutes like in real life. A lot of dramatic tension carries the action between plays." Finnegan also criticized the artwork, saying, "any episode [of the show] without a game is clearly farmed out to an inferior animation studio". Chris Beveridge from Mania Entertainment wrote that "Eyeshield 21" "has a good solid story idea, showing a young man finding his way through sports by finding friends and realizing he has potential, but it is so sidelined so often that it's frustrating to see it deal with situations as it does."


title: Twelve Years a Slave

text: Twelve Years a Slave is an 1853 memoir and slave narrative by American Solomon Northup as told to and written by David Wilson. Northup, a black man who was born free in New York state, details himself being tricked to go to Washington, D.C., where he was kidnapped and sold into slavery in the Deep South. He was in bondage for 12 years in Louisiana before he was able to secretly get information to friends and family in New York, who in turn secured his release with the aid of the state. Northup's account provides extensive details on the slave markets in Washington, D.C. and New Orleans, and describes at length cotton and sugar cultivation and slave treatment on major plantations in Louisiana.


title: Twelve Years a Slave

text: The work was published eight years before the Civil War by Derby & Miller of Auburn, New York, soon after Harriet Beecher Stowe's best-selling novel about slavery, "Uncle Tom's Cabin" (1852), to which it lent factual support. Northup's book, dedicated to Stowe, sold 30,000 copies, making it a bestseller in its own right.


title: Twelve Years a Slave

text: After being published in several editions in the 19th century and although later cited by specialist scholarly works on slavery in the United States, the memoir fell into public obscurity for nearly 100 years. It was re-discovered on separate occasions by two Louisiana historians, Sue Eakin (Louisiana State University at Alexandria) and Joseph Logsdon (University of New Orleans). In the early 1960s, they researched and retraced Solomon Northup's journey and co-edited a historically annotated version that was published by Louisiana State University Press (1968).


title: Twelve Years a Slave

text: The memoir has been adapted as two film versions, produced as the 1984 PBS television film "Solomon Northup's Odyssey" and the 2013 film "12 Years a Slave", which won multiple Oscars including Best Picture.


title: Twelve Years a Slave

text: In his home town of Saratoga Springs, New York, Solomon Northup, a free negro and a skilled carpenter and violinist, was approached by two circus promoters, Brown and Hamilton. They offered him a brief, high-paying job as a musician with their traveling circus. Without informing his wife, who was away at work in a nearby town, he traveled with the strangers to downstate New York and Washington, D.C. Soon after arriving in the capital, he awoke to find himself drugged, bound, and in the cell of a slave pen. When Northup asserted his rights as a free man, he was beaten and warned never again to mention his free life in New York.


title: Twelve Years a Slave

text: Transported by ship to New Orleans, Northup and other enslaved black people contracted smallpox and one died. In transit, Northup implored a sympathetic sailor to send a letter to his family. The letter arrived safely, but, lacking knowledge of his final destination, Northup's family was unable to effect his rescue.


title: Twelve Years a Slave

text: Northup's first owner was William Prince Ford, who ran a lumber mill on a bayou of the Red River. Northup subsequently had several other owners, less humane than Ford, during his twelve-year bondage. At times, his carpentry and other skills contributed to his being treated relatively well, but he also suffered extreme cruelty. On two occasions, he was attacked by John Tibeats, a white man he was leased to, and defended himself, for which he suffered severe reprisals. After about two years of enslavement, Northup was sold to Edwin Epps, a notoriously cruel cotton planter. Epps held Northup enslaved for 10 years, during which time he assigned the New Yorker to various roles from cotton picker, to hauler to driver, which required Northup to oversee the work of fellow slaves and punish them for undesirable behavior. While on Epps' plantation, Northup became friends with a slave girl named Patsey, whom he writes about briefly in the book.


title: Twelve Years a Slave

text: After being beaten for claiming his free status in Washington, D.C., Northup in the ensuing 12 years did not reveal his true history again to a single person, slave or owner. Finally he confided his story to Samuel Bass, a white carpenter and abolitionist from Canada working at the Epps plantation (to build the Edwin Epps House). Bass, at great risk to himself, sent letters to Northup's wife and friends in Saratoga. Parker, a white shopkeeper, received one of the letters and sought assistance from Henry B. Northup, a white attorney and politician whose family had held and freed Solomon Northup's father and with whom Solomon had a longtime friendship. Henry contacted New York state officials. As the state had passed a law in 1840 to provide financial resources for the rescue of citizens kidnapped into slavery, the Governor appointed Henry Northup as an agent to travel to Louisiana and work with law enforcement to free Solomon. Once in Louisiana, Henry Northup hired local Avoyelles Parish attorney, John P. Waddill, to assist in securing Solomon Northup's freedom. After a variety of bureaucratic measures and searches were undertaken, the attorney succeeded in locating Solomon and freeing him from the plantation. Northup later filed charges against the men who sold him into slavery but was unsuccessful in his suit. He returned to New York and reunited with his family there.


title: Twelve Years a Slave

text: Questions were often raised about accuracy or authenticity of books about slavery, including slave narratives. Similarities between Northup's book and Harriet Beecher Stowe's novel "Uncle Tom's Cabin" have been noted by critics. Stowe's book was published a year before Northup's memoir but by the time she published her rebuttal to critics about accuracy in her "A Key to Uncle Tom's Cabin", she referred to his story, which had been publicized in newspaper accounts. Stowe wrote,


title: Twelve Years a Slave

text: It is a singular coincidence that this man was carried to a plantation in the Red River country, that same region where the scene of Tom's captivity was laid; and his account of this plantation, his mode of life there, and some incidents which he describes, form a striking parallel to that history.


title: Twelve Years a Slave

text: Northup's account confirms Stowe's fictional portrayal of conditions in Louisiana, as the area where Northup was enslaved was close to the fictional setting of Simon Legree's plantation on the Red River. Northup expresses other arguments against slavery. For instance, "Uncle Tom's Cabin" focuses on how the legal system prevents even kind owners from treating slaves well and how it releases cruel owners from liabilities for their treatment of slaves.


title: Twelve Years a Slave

text: Such themes appear in Northup's narrative, too. Writing about this work, Eric Herschtal noted that "Slave narratives were never intended to give an unbiased view. They were antislavery polemics meant to bring down the institution." The fact that these works had a purpose was similar to other published works.


title: Twelve Years a Slave

text: Herschtal emphasizes that Northup expressed compassion in his account, quoting him: "It is not the fault of the slaveholder that he is cruel," Northup writes, "so much as it is the fault of the system under which he lives."


title: Twelve Years a Slave

text: Northup's first-person account of his twelve years of bondage captured attention in the national political debate over slavery that took place in the years leading up to the Civil War. It drew endorsements from major Northern newspapers, anti-slavery organizations, and evangelical groups. It "sold three times as many copies as Frederick Douglass's slave narrative in its first two years."


title: Twelve Years a Slave

text: Northup's account describes the daily life of slaves at Bayou Boeuf in Louisiana, their diet and living conditions, the relationship between master and slave, and the means that slave catchers used to recapture runaways. His account shares some details similar to those of authors who were escaped slaves, such as Frederick Douglass, Harriet Jacobs, and William Wells Brown. However, Northup was unique in documenting his being kidnapped as a free man from the North and sold into slavery. His perspective was always to compare what he saw to what he knew before while living as a free man in a free state. While there were hundreds of such kidnappings, he was among the few persons who gained freedom again.


title: Twelve Years a Slave

text: Early and mid-twentieth century historians of slavery, Kenneth Stampp, Stanley Elkins, and Ulrich Bonnell Phillips, endorsed the historical accuracy of the book. Eakin and Logsdon in 1968, wrote: "In the last analysis, [the] narrative deserves to be believed, not simply because [Northup] seems to be talking reasonably, not merely because he adorns his tale with compelling and persuasive details. At every point where materials exist for checking his account, it can be verified." These materials include trial records, correspondence, diary, and slave sale records.


title: Twelve Years a Slave

text: While "Twelve Years a Slave" is the best-known example of someone who was kidnapped and later freed – albeit through extraordinary efforts – historians have begun to research and present other cases. Most of the known court cases of freedom suits related to kidnapping victims were filed in New Orleans, although some were in border states such as Missouri. One such suit took place in Tuscaloosa, Alabama, where Cornelius Sinclair, a free black man from Philadelphia, Pennsylvania, had been sold after being kidnapped in August 1825 and transported South with some younger free blacks. A total of about 20 young blacks disappeared from the Philadelphia area that summer, some survivors sold into slavery in Mississippi. Helped by the intervention of Philadelphia mayor Joseph Watson, most of those kidnapped were returned free to Philadelphia by June 1826, but Sinclair's odyssey was longer. He was freed in 1827 by a unanimous verdict of an all-white jury.


title: Twelve Years a Slave

text: After additional printings in the 19th century, the book went out of print until 1968, when historians Joseph Logsdon and Sue Eakin restored it to prominence. Eakin discovered the story as a child growing up in Louisiana plantation countrythe owner of a first edition showed her the book, after finding it in a former plantation home.


title: Twelve Years a Slave

text: Years later, Logsdon had a student from an old Louisiana family who brought a copy of the original 1853 book to class; her family had owned it for more than a century. Together Logsdon and Eakin studied Northup's account, documenting it through the slave sales records of Washington, D.C. and New Orleans, by retracing his journey and bondage in Bayou Boeuf plantation country in central Louisiana and through its records, and documenting his New York State origins. They found his father's freeman's decree, and the case files for the legal work that restored Northup's freedom and prosecuted his abductors. In 1968, Eakin and Logsdon's thoroughly annotated edition of the original book was published by Louisiana State University Press, shedding new light on Northup's account and establishing its historic significance. That book has been widely used by scholars and in classrooms for more than 40 years, and is still in print.


title: Twelve Years a Slave

text: In 1998, Logsdon was invited by scholars in upstate New York to participate in a search for Solomon's grave. However, bad weather prevented the search that year, and Logsdon died the following June 1999. In 2007, shortly before her death at age 90, Eakin completed an updated and expanded version of their book; it includes more than 150 pages of new background material, maps, and photographs. In 2013, e-book and audiobook versions of her final definitive edition were released in her honor. With permission, scholars may use Eakin's lifetime archives through The Sue Eakin Collection, Louisiana State University at Alexandria, Louisiana. The Joseph Logsdon Archives are available at the University of New Orleans.


title: Twelve Years a Slave

text: Historian Jesse Holland noted in a 2009 interview that he had relied on Northup's memoir and detailed description of Washington in 1841 to identify the location of some slave markets in the capital. Holland has also researched the roles of African-American slaves who, as skilled laborers, helped build some of the important public buildings in Washington, including the Capitol and part of the original Executive Mansion.


title: Francesinha

text: Francesinha ( meaning "Frenchie") is a Portuguese sandwich originally from Porto, made with bread, wet-cured ham, linguiça, fresh sausage like chipolata, steak or roast meat, and covered with melted cheese and a hot and thick spiced tomato and beer sauce. It is typically served with french fries.


title: Francesinha

text: Daniel David de Silva, a returned French emigrant from France and Belgium, tried to adapt the croque-monsieur to the Portuguese taste when he moved to Porto. He first made the sandwich with local meats and his special sauce in 1953 at 'A "Regaleira"', a restaurant in Rua do Bonjardim, Porto; the francesinha quickly became a very popular dish and deeply associated with the city, although it can be found in many other places in Portugal. A classic francesinha meal would include the sandwich, surrounded on a bed of French fries doused in the famous , and complemented with a "fino", a draught beer.


title: Francesinha

text: There is no standard recipe for the francesinha. Different restaurants in Portugal have special variations, such as:


title: Francesinha

text: The (special francesinha) is a francesinha with egg and/or potato chips. Other variations of the original include fillings such as pork, chicken, pastrami, tuna, cod and vegetarian options.


title: Francesinha

text: Francesinha sauce varies, with each establishment having its variation. The only common ingredient is beer. Most, though not all, sauces are tomato based and vary in their degree of spiciness. The color is usually red or orange.


title: Francesinha

text: "Francesinha poveira" is a form of francesinha distinctive to Póvoa de Varzim, north of Porto, created in the early 1960s. The poveira form uses different bread and sauce to form a sandwich that can be eaten by hand.


title: Francesinha

text: "Pica-pau" is a breadless variant in which a steak is cut into bite-sized pieces and covered with sauce. The name "pica-pau" (woodpecker) references the traditional means of consumption with small skewers or toothpicks—making the diner "peck" at the dish.


title: Francesinha

text: "The Daily Meal" included the francesinha in their article "12 Life-Changing Sandwiches You've Never Heard Of".


title: Expert system

text: In artificial intelligence, an expert system is a computer system emulating the decision-making ability of a human expert.


title: Expert system

text: Expert systems are designed to solve complex problems by reasoning through bodies of knowledge, represented mainly as if–then rules rather than through conventional procedural code. The first expert systems were created in the 1970s and then proliferated in the 1980s. Expert systems were among the first truly successful forms of artificial intelligence (AI) software.


title: Expert system

text: An expert system is divided into two subsystems: the inference engine and the knowledge base. The knowledge base represents facts and rules. The inference engine applies the rules to the known facts to deduce new facts. Inference engines can also include explanation and debugging abilities.


title: Expert system

text: Soon after the dawn of modern computers in the late 1940s and early 1950s, researchers started realizing the immense potential these machines had for modern society. One of the first challenges was to make such machines capable of “thinking” like humans – in particular, making these machines capable of making important decisions the way humans do. The medical/healthcare field presented the tantalizing challenge of enabling these machines to make medical diagnostic decisions.


title: Expert system

text: Thus, in the late 1950s, right after the information age had fully arrived, researchers started experimenting with the prospect of using computer technology to emulate human decision making. For example, biomedical researchers started creating computer-aided systems for diagnostic applications in medicine and biology. These early diagnostic systems used patients’ symptoms and laboratory test results as inputs to generate a diagnostic outcome.


title: Expert system

text: These systems were often described as the early forms of expert systems. However, researchers realized that there were significant limitations when using traditional methods such as flow charts,


title: Expert system

text: This previous situation gradually led to the development of expert systems, which used knowledge-based approaches. These expert systems in medicine were the MYCIN expert system, the INTERNIST-I expert system and later, in the middle of the 1980s, the CADUCEUS.


title: Expert system

text: Expert systems were formally introduced around 1965 by the Stanford Heuristic Programming Project led by Edward Feigenbaum, who is sometimes termed the "father of expert systems"; other key early contributors were Bruce Buchanan and Randall Davis. The Stanford researchers tried to identify domains where expertise was highly valued and complex, such as diagnosing infectious diseases (Mycin) and identifying unknown organic molecules (Dendral). The idea that "intelligent systems derive their power from the knowledge they possess rather than from the specific formalisms and inference schemes they use" – as Feigenbaum said – was at the time a significant step forward, since the past research had been focused on heuristic computational methods, culminating in attempts to develop very general-purpose problem solvers (foremostly the conjunct work of Allen Newell and Herbert Simon). Expert systems became some of the first truly successful forms of artificial intelligence (AI) software.


title: Expert system

text: Research on expert systems was also active in France. While in the US the focus tended to be on rules-based systems, first on systems hard coded on top of LISP programming environments and then on expert system shells developed by vendors such as Intellicorp, in France research focused more on systems developed in Prolog. The advantage of expert system shells was that they were somewhat easier for nonprogrammers to use. The advantage of Prolog environments was that they were not focused only on "if-then" rules; Prolog environments provided a much better realization of a complete first order logic environment.


title: Expert system

text: In the 1980s, expert systems proliferated. Universities offered expert system courses and two-thirds of the Fortune 500 companies applied the technology in daily business activities. Interest was international with the Fifth Generation Computer Systems project in Japan and increased research funding in Europe.


title: Expert system

text: In 1981, the first IBM PC, with the PC DOS operating system, was introduced. The imbalance between the high affordability of the relatively powerful chips in the PC, compared to the much more expensive cost of processing power in the mainframes that dominated the corporate IT world at the time, created a new type of architecture for corporate computing, termed the client–server model. Calculations and reasoning could be performed at a fraction of the price of a mainframe using a PC. This model also enabled business units to bypass corporate IT departments and directly build their own applications. As a result, client-server had a tremendous impact on the expert systems market. Expert systems were already outliers in much of the business world, requiring new skills that many IT departments did not have and were not eager to develop. They were a natural fit for new PC-based shells that promised to put application development into the hands of end users and experts. Until then, the main development environment for expert systems had been high end Lisp machines from Xerox, Symbolics, and Texas Instruments. With the rise of the PC and client-server computing, vendors such as Intellicorp and Inference Corporation shifted their priorities to developing PC-based tools. Also, new vendors, often financed by venture capital (such as Aion Corporation, Neuron Data, Exsys, and many others), started appearing regularly.


title: Expert system

text: The first expert system to be used in a design capacity for a large-scale product was the SID (Synthesis of Integral Design) software program, developed in 1982. Written in LISP, SID generated 93% of the VAX 9000 CPU logic gates. Input to the software was a set of rules created by several expert logic designers. SID expanded the rules and generated software logic synthesis routines many times the size of the rules themselves. Surprisingly, the combination of these rules resulted in an overall design that exceeded the capabilities of the experts themselves, and in many cases out-performed the human counterparts. While some rules contradicted others, top-level control parameters for speed and area provided the tie-breaker. The program was highly controversial but used nevertheless due to project budget constraints. It was terminated by logic designers after the VAX 9000 project completion.


title: Expert system

text: During the years before the middle of the 1970s, the expectations of what expert systems can accomplish in many fields tended to be extremely optimistic. At the beginning of these early studies, researchers were hoping to develop entirely automatic (i.e., completely computerized) expert systems. The expectations of people of what computers can do were frequently too idealistic. This situation radically changed after Richard M. Karp published his breakthrough paper: “Reducibility among Combinatorial Problems” in the early 1970s. Thanks to Karp's work, together with other scholars, like Hubert L. Dreyfus, it became clear that there are certain limitations and possibilities when one designs computer algorithms. His findings describe what computers can do and what they cannot do. Many of the computational problems related to this type of expert systems have certain pragmatic limitations. These findings laid down the groundwork that led to the next developments in the field.


title: Expert system

text: In the 1990s and beyond, the term "expert system" and the idea of a standalone AI system mostly dropped from the IT lexicon. There are two interpretations of this. One is that "expert systems failed": the IT world moved on because expert systems did not deliver on their over hyped promise. The other is the mirror opposite, that expert systems were simply victims of their success: as IT professionals grasped concepts such as rule engines, such tools migrated from being standalone tools for developing special purpose "expert" systems, to being one of many standard tools. Other researchers suggest that Expert Systems caused inter-company power struggles when the IT organization lost its exclusivity in software modifications to users or Knowledge Engineers. Many of the leading major business application suite vendors (such as SAP, Siebel, and Oracle) integrated expert system abilities into their suite of products as a way of specifying business logic – rule engines are no longer simply for defining the rules an expert would use but for any type of complex, volatile, and critical business logic; they often go hand in hand with business process automation and integration environments.


title: Expert system

text: The limitations of the previous type of expert systems have urged researchers to develop new types of approaches. They have developed more efficient, flexible, and powerful approaches in order to simulate the human decision-making process. Some of the approaches that researchers have developed are based on new methods of artificial intelligence (AI), and in particular in machine learning and data mining approaches with a feedback mechanism. Recurrent neural networks often take advantage of such mechanisms. Related is the discussion on the disadvantages section.


title: Expert system

text: Modern systems can incorporate new knowledge more easily and thus update themselves easily. Such systems can generalize from existing knowledge better and deal with vast amounts of complex data. Related is the subject of big data here. Sometimes these type of expert systems are called "intelligent systems."


title: Expert system

text: An expert system is an example of a knowledge-based system. Expert systems were the first commercial systems to use a knowledge-based architecture. In general view, an expert system includes the following components: a knowledge base, an inference engine, an explanation facility, a knowledge acquisition facility, and a user interface.


title: Expert system

text: The knowledge base represents facts about the world. In early expert systems such as Mycin and Dendral, these facts were represented mainly as flat assertions about variables. In later expert systems developed with commercial shells, the knowledge base took on more structure and used concepts from object-oriented programming. The world was represented as classes, subclasses, and instances and assertions were replaced by values of object instances. The rules worked by querying and asserting values of the objects.


title: Expert system

text: The inference engine is an automated reasoning system that evaluates the current state of the knowledge-base, applies relevant rules, and then asserts new knowledge into the knowledge base. The inference engine may also include abilities for explanation, so that it can explain to a user the chain of reasoning used to arrive at a particular conclusion by tracing back over the firing of rules that resulted in the assertion.


title: Expert system

text: There are mainly two modes for an inference engine: forward chaining and backward chaining. The different approaches are dictated by whether the inference engine is being driven by the antecedent (left hand side) or the consequent (right hand side) of the rule. In forward chaining an antecedent fires and asserts the consequent. For example, consider the following rule:


title: Expert system

text: A simple example of forward chaining would be to assert Man(Socrates) to the system and then trigger the inference engine. It would match R1 and assert Mortal(Socrates) into the knowledge base.


title: Expert system

text: Backward chaining is a bit less straight forward. In backward chaining the system looks at possible conclusions and works backward to see if they might be true. So if the system was trying to determine if Mortal(Socrates) is true it would find R1 and query the knowledge base to see if Man(Socrates) is true. One of the early innovations of expert systems shells was to integrate inference engines with a user interface. This could be especially powerful with backward chaining. If the system needs to know a particular fact but does not, then it can simply generate an input screen and ask the user if the information is known. So in this example, it could use R1 to ask the user if Socrates was a Man and then use that new information accordingly.


title: Expert system

text: The use of rules to explicitly represent knowledge also enabled explanation abilities. In the simple example above if the system had used R1 to assert that Socrates was Mortal and a user wished to understand why Socrates was mortal they could query the system and the system would look back at the rules which fired to cause the assertion and present those rules to the user as an explanation. In English, if the user asked "Why is Socrates Mortal?" the system would reply "Because all men are mortal and Socrates is a man". A significant area for research was the generation of explanations from the knowledge base in natural English rather than simply by showing the more formal but less intuitive rules.


title: Expert system

text: As expert systems evolved, many new techniques were incorporated into various types of inference engines. Some of the most important of these were:


title: Expert system

text: The goal of knowledge-based systems is to make the critical information required for the system to work explicit rather than implicit. In a traditional computer program the logic is embedded in code that can typically only be reviewed by an IT specialist. With an expert system the goal was to specify the rules in a format that was intuitive and easily understood, reviewed, and even edited by domain experts rather than IT experts. The benefits of this explicit knowledge representation were rapid development and ease of maintenance.


title: Expert system

text: Ease of maintenance is the most obvious benefit. This was achieved in two ways. First, by removing the need to write conventional code, many of the normal problems that can be caused by even small changes to a system could be avoided with expert systems. Essentially, the logical flow of the program (at least at the highest level) was simply a given for the system, simply invoke the inference engine. This also was a reason for the second benefit: rapid prototyping. With an expert system shell it was possible to enter a few rules and have a prototype developed in days rather than the months or year typically associated with complex IT projects.


title: Expert system

text: A claim for expert system shells that was often made was that they removed the need for trained programmers and that experts could develop systems themselves. In reality, this was seldom if ever true. While the rules for an expert system were more comprehensible than typical computer code, they still had a formal syntax where a misplaced comma or other character could cause havoc as with any other computer language. Also, as expert systems moved from prototypes in the lab to deployment in the business world, issues of integration and maintenance became far more critical. Inevitably demands to integrate with, and take advantage of, large legacy databases and systems arose. To accomplish this, integration required the same skills as any other type of system.


title: Expert system

text: The most common disadvantage cited for expert systems in the academic literature is the knowledge acquisition problem. Obtaining the time of domain experts for any software application is always difficult, but for expert systems it was especially difficult because the experts were by definition highly valued and in constant demand by the organization. As a result of this problem, a great deal of research in the later years of expert systems was focused on tools for knowledge acquisition, to help automate the process of designing, debugging, and maintaining rules defined by experts. However, when looking at the life-cycle of expert systems in actual use, other problems – essentially the same problems as those of any other large system – seem at least as critical as knowledge acquisition: integration, access to large databases, and performance.


title: Expert system

text: Performance could be especially problematic because early expert systems were built using tools (such as earlier Lisp versions) that interpreted code expressions without first compiling them. This provided a powerful development environment, but with the drawback that it was virtually impossible to match the efficiency of the fastest compiled languages (such as C). System and database integration were difficult for early expert systems because the tools were mostly in languages and platforms that were neither familiar to nor welcome in most corporate IT environments – programming languages such as Lisp and Prolog, and hardware platforms such as Lisp machines and personal computers. As a result, much effort in the later stages of expert system tool development was focused on integrating with legacy environments such as COBOL and large database systems, and on porting to more standard platforms. These issues were resolved mainly by the client–server paradigm shift, as PCs were gradually accepted in the IT environment as a legitimate platform for serious business system development and as affordable minicomputer servers provided the processing power needed for AI applications.


title: Expert system

text: Another major challenge of expert systems emerges when the size of the knowledge base increases. This causes the processing complexity to increase. For instance, when an expert system with 100 million rules was envisioned as the ultimate expert system, it became obvious that such system would be too complex and it would face too many computational problems. An inference engine would have to be able to process huge numbers of rules to reach a decision.


title: Expert system

text: How to verify that decision rules are consistent with each other is also a challenge when there are too many rules. Usually such problem leads to a satisfiability (SAT) formulation. This is a well-known NP-complete problem Boolean satisfiability problem. If we assume only binary variables, say n of them, and then the corresponding search space is of size 2formula_2. Thus, the search space can grow exponentially.


title: Expert system

text: There are also questions on how to prioritize the use of the rules in order to operate more efficiently, or how to resolve ambiguities (for instance, if there are too many else-if sub-structures within a single rule) and so on.


title: Expert system

text: Other problems are related to the overfitting and overgeneralization effects when using known facts and trying to generalize to other cases not described explicitly in the knowledge base. Such problems exist with methods that employ machine learning approaches too.


title: Expert system

text: Another problem related to the knowledge base is how to make updates of its knowledge quickly and effectively. Also how to add a new piece of knowledge (i.e., where to add it among many rules) is challenging. Modern approaches that rely on machine learning methods are easier in this regard.


title: Expert system

text: Because of the above challenges, it became clear that new approaches to AI were required instead of rule-based technologies. These new approaches are based on the use of machine learning techniques, along with the use of feedback mechanisms.


title: Expert system

text: The key challenges that expert systems in medicine (if one considers computer-aided diagnostic systems as modern expert systems), and perhaps in other application domains, include issues related to aspects such as: big data, existing regulations, healthcare practice, various algorithmic issues, and system assessment.


title: Expert system

text: Hayes-Roth divides expert systems applications into 10 categories illustrated in the following table. The example applications were not in the original Hayes-Roth table, and some of them arose well afterward. Any application that is not footnoted is described in the Hayes-Roth book. Also, while these categories provide an intuitive framework to describe the space of expert systems applications, they are not rigid categories, and in some cases an application may show traits of more than one category.


title: Expert system

text: Hearsay was an early attempt at solving voice recognition through an expert systems approach. For the most part this category of expert systems was not all that successful. Hearsay and all interpretation systems are essentially pattern recognition systems—looking for patterns in noisy data. In the case of Hearsay recognizing phonemes in an audio stream. Other early examples were analyzing sonar data to detect Russian submarines. These kinds of systems proved much more amenable to a neural network AI solution than a rule-based approach.


title: Expert system

text: CADUCEUS and MYCIN were medical diagnosis systems. The user describes their symptoms to the computer as they would to a doctor and the computer returns a medical diagnosis.


title: Expert system

text: Dendral was a tool to study hypothesis formation in the identification of organic molecules. The general problem it solved—designing a solution given a set of constraints—was one of the most successful areas for early expert systems applied to business domains such as salespeople configuring Digital Equipment Corporation (DEC) VAX computers and mortgage loan application development.


title: Expert system

text: GARVAN-ES1 was a medical expert system, developed at the Garvan Institute of Medical Research, that provided automated clinical diagnostic comments on endocrine reports from a pathology laboratory. It was one of the first medical expert systems to go into routine clinical use internationally and the first expert system to be used for diagnosis daily in Australia. The system was written in "C" and ran on a PDP-11 in 64K of memory. It had 661 rules that were compiled; not interpreted.