In the previous video, we understood the importance of design comprehension and how experienced designers comprehend a given design. We also interacted with the Verisim learning environment. Verisim helped us understand how to comprehend a given design by tracing various scenarios in the design. Okay, so we have modeled, created a design, comprehended and now we also have an integrated understanding of the design. Yes, along with comprehending a design, we also have to evaluate whether the design is correct. Design is correct? In what sense? Can you help me understand this with an example? Yes, let's take an example from a non-software context. It might help us understand the concept better. Let's say that you are paying money for a Tiffin service which provides you with three meals, breakfast, lunch and dinner every day. So what are different scenarios for which you will not be satisfied with the Tiffin service? You can pause this video, write down your responses and then proceed. So the first thing is that I want my food to be delivered on time and I don't want any mix ups happening. For example, the service shouldn't be giving me breakfast for lunch. Yes, exactly. So what you actually mentioned now, these are the basic requirements, right? The Tiffin service should make sure that these basic requirements are satisfied. This is known as correctness. Okay, so going back to the software design context, we need to ensure the correctness of the design. We make sure the design satisfies all the requirements. We can say that the design is correct in some sense. Yes, you're right. When you check for correctness, you ensure that the design satisfies all that your system should do. Correctness is the extent to which a program behaves according to its specification. Learners, this is what you did in verisim as well. Using design tracing, you checked whether various scenarios in the design correctly satisfied all the requirements of the automated door locking system. Correctness is one of the functional requirements of the system. Functional requirements describe what the system should do. We need to ensure that all the functional requirements are satisfied by the design. The functional requirements are satisfied is one way to evaluate the given design. But isn't the only way? Are there other perspectives we need to consider while evaluating a given design? Yes, there are several other ways to evaluate a software design. It is necessary to evaluate a design against various quality attributes. Quality attributes? Can you help me understand this with an example? Yes, let us go back to the defense service example. What else do you expect from the defense service? Okay, next, I want the service to be reliable. For example, if I miss more than 3 meals a week, I wouldn't be happy. Exactly. This is termed as reliability. Reliability is the extent to which a program behaves the same way over time in the same operating environment. In case of software, we need to ensure that it doesn't crash often. Otherwise, users will get frustrated. For example, in a mobile wallet like Amazon Pay, reliability is even more important. We must ensure that the wallet reliably handles all operations, especially important operations like withdrawal and deposit. I also want the service to handle unexpected situations reasonably well. For example, if the main chef falls safe, is there a replacement? Is there any other option to serve the customers? Okay, so this is similar to the quality attribute of being robust even in unexpected situations. Robustness is the extent to which a program can recover from errors or unexpected input. For example, in a mobile wallet system like Amazon Pay, we have to ensure that the service handles unexpected input like negative numbers and large numbers and high traffic as well. So, while checking for quality attributes like reliability and robustness, we are in a way checking how the system is behaving and not exactly checking the system requirements. So, are these quality attributes different from the functional requirements of the system? Yes, you are right. Attributes like reliability and robustness are known as the non-functional requirements of the system. Non-functional requirements essentially specify how the system should behave. For example, we looked at two non-functional requirements, reliability and robustness. Okay, so functional and non-functional requirements have to be considered while designing, creating and evaluating the system. Yes, you are right. To summarize, in this video, we discussed functional and non-functional requirements. There are other non-functional requirements such as performance, portability, security and so on. Do check out the additional resources for more information.


If you know from A Course in Miracles that there's in the manual for teachers the stages of the development of trust. And I believe it's the second stage it will seem as if, Jesus says, it will seem as if things are being taken away from you. This is what happens in the second stage of the development of trust.  And Jesus is telling us it's not really what's happening, it's just that your mind is starting to devalue the things of this world. That's why they seem to be leaving.  Are you going to take it all from me? You know, the ego is kicking and fighting and screaming about everything that it thinks it has, which it invented. So it thinks it has it, it thinks it controls it, it thinks it possesses it, it thinks it makes it happy, it thinks it will feel totally deserted. I can't live if living is without you. I can't give, I can't give anymore.  And actually the mind is just devaluing the world. That's why things seem to be going bye-bye. It could be persons, it could be things, it could be houses, it could be countries, it could be children, it could be anything. They're all part of the images and it will seem as if things are being taken away. But that's just the second stage of the development of trust. So we've had that happen.  Really good friends, close friends, and then all of a sudden like they're scooped up and you don't ever hear from them again. That happens. It seems perplexing to the ego. But again, it's just that certain things are being devalued in the mind and it's making way for more to come. What's in there saying something about when God closes the door, He always opens a window.  That's what's happening. There's no loss involved. We never lose anything actually. It's just these shifting symbols that are taking us higher and higher and higher like an ascending staircase that's just taking you higher and higher in awareness. And there's really no loss involved at all. That's just an ego interpretation.


The Jack Benny program, presented by Lucky Strike. Be happy, go lucky, be happy, go lucky, strike the day. Try every brand in this great land and you'll agree with me. The finest tasting cigarette is LSMFT. Yes, sirree, Lucky's taste better than any other cigarette. Oh, we're heading for a picnic and we'll have a lot of fun with better tasting Lucky Strikes for each and every one. Honestly, Lucky's taste better than any other cigarette. Be happy, go lucky, be happy, go lucky, strike the day. Friends, Lucky's taste better than any other cigarette. And here's the reason, fine tobacco and only fine tobacco always gives you the enjoyment of a better tasting cigarette. And LSMFT, Lucky Strike means fine tobacco. Tobacco that smokes smooth and mild, that gives you better taste with every puff. Yes, Lucky Strike and Lucky Strike alone gives you an extra measure of smoking pleasure.  You will agree, Lucky's taste better than any other cigarette. Be happy, go lucky, go lucky, strike the day. Remember, Lucky's taste better than any other cigarette. Benny with Murray Livingston, Phil Harris, Rochester, Dennis Day, and yours truly, Don Wilson. Ladies and gentlemen, our next Sunday, Jack Benny will be in New York doing another television show. And right now, he's home packing for the trip. Gee, this is my fourth trip to New York this season. I like to travel. No, Polly, you can't go with me this time. I wonder, I don't know where to live in New York. I wonder if I should stay at the Acme Plaza Hotel again. Yeah, I guess so. They're so considerate. They always give me a room with congenial people. Yeah, I guess I'll stay there. Oh, Rochester. Yes, boss. I hope you're packing enough clothes. You know, we'll be gone for 10 days. Oh, yes, I've packed enough for both of us.  No, no, Rochester, it's my tweed suit. Remember, I won it back.  But remember, I had four aces. Oh, yeah, I only had three.  Now, finish the packing and remember what I told you. Remember what I told you to put in a suitcase? Oh, boy. Rochester, I don't care what you say, I'm taking it with me. So put it in my suitcase. I want to wear it on my arrival in New York. Boss, if people want to throw ticket, they'll throw it. You don't have to wear that old army cap. Well, maybe you're right. Anyway, after you finish packing, go out and polish the car. Polish the car? Why? Why, because we're driving it to New York. That car? Rochester, there's nothing to handle. I'm driving my car to New York. And to keep the cost down, I put an ad in the paper for passengers to share expenses. In fact, I expect several people to drop in and see me. Well, I'm waiting. How come you have no comment on that? I never even fear with a plot line. Hey, maybe that's someone now. Come in. Oh, it's you, Dennis. Come on in. Thank you. Dennis, what have you got in that package? My pajamas. Can I sleep here tonight? Well, I don't see why not. Why don't you sleep at home? Oh, I don't like to be in a big house alone. Alone? Yeah, my parents did it again. Did what? Moved away and didn't tell me where. For heaven's sake, Dennis, what did you do wrong this time? Well, if I tell you, you'll only side in with them. Well, not necessarily, Dennis. What did you do? I got up early this morning and fed the goldfish. Well, why should your parents get mad at that? I fed them to our cat. Dennis, that's the most awful thing that I've ever... I knew you'd side in with them. Well, certainly, who could be on your side? The cat.  But right now, leave me alone because I'm busy packing. Oh, all right. You going someplace? Yes, I'm going to New York. See, next Sunday, I'm doing my television show. Oh, who's going to be with you this time, Mr. Benny? Well, I'm going to have Rochester and Mary and Bob Crosby and another special guest. Who? Well, I'll give you a hint. He's one of the world's greatest golfers. Uh-huh. He won the U.S. Open, the PGA, and the Masters Tournament in Augusta, Georgia. Uh-huh. And they just made a picture about him at 20th Century Fox called Follow the Sun. Now, who is it? Ben Hogan. Hey. Hey, that's right, Dennis. And the name of the actor who played his part in the picture is Glenn Schwinn. No, no, Dennis. That's Glenn Ford. That's Glenn Ford. I know, but if you mention Schwinn, they send you a bicycle. Well, Dennis, I didn't think you'd stoop so low as to tell them to put a bell on mine, will you? What's the matter there, early? Something off of your script? Well, wait, Dennis. What song? What song are you going to do on the program today? Well, I'm going to sing a wonderful number. I just recorded for RCA Victor called Mr. in Mississippi. Well, let me hear it, Dennis, before you put your on your pajamas and go. Oh, hold it a minute, kid. OK. There's the phone. Hello? Long distance? Yes. Benny? The name is Benny. Well, you are, as a matter of fact, next Sunday. Here's your party. Oh. What are you doing in San Luis Obispo? Me and my band played at one of the dance halls up here last night. You did? How did things go? Well, that's what I'm calling about. How would you like to do a little bail bond business?  I ain't calling from no drug store. Health to all from city hall. What happened at the dance that you boys got in such trouble? Well, I get this call to come up here and play for the San Luis Obispo chapter of the Society for the Prevention of Cruel Data Soft Shell Crabs. I didn't know they had a chapter in San Luis Obispo. The main office is in Pizmo Beach. Anyway, we come to the hall. We set up our instruments and start playing for the dance. Everything goes long fine until about 10.30 when it's time for the walls contest. Suddenly, someone in the crowd yells out, hey, Aris, how about singing? That's what I like about the sound. Operator, you keep out of it. Boy, I start singing that little number that made me famous. That was at 10.30. Yeah, and at 1 o'clock in the morning with 20 courses to go, somebody dyed my hair with a ripe tomato. No. And before you could say spade, coolly, everybody started throwing things at us. Them soft shell crabs are murder. Well, you mean they threw soft shell crabs at you? No, the crabs were throwing them too. That must have been quite a rubble. You ain't kidding, Dad. Everybody was in there fighting but Frankie. Frankie Remling?  Gee. At this, he jumps up, runs around at the back of the hall and pulls the main light switch. But they could still see the bandstand and we're getting it from all directions. Well, Phil, how could they see the bandstand if the lights were off? My drummer's head glows in the dark. Oh, yes, you shouldn't have painted that moon on it. All right, all right. And then about 2 o'clock when the police came in, Phil, what? Hang up. Maybe you're right, Jackson. When you come here on, it just gets ridiculous. How about that bail money? I'll send it. I'll send it. Now, for 18 men at a monster... I know how much at a monster. This is the third time this year. Goodbye. Goodbye, Jackson. That Harris can get into more trouble than anybody I ever saw. Will you keep quiet so I can sing? Oh, yes, I'm sorry, Dennis. Go ahead. Mr. and Mississippi was on Mississippi River boat. My teacher was a gambler. The slickest one afloat. My teacher was a gambler. He taught me not to gamble. Restless river, tiny village. A house, a little... I'd be... Mr. and Mississippi, are you sending me a record of it? Well, you can buy one for 85 cents. Well, what's on the other side? Fuel train by Lily Pond.  I just can't shout anymore. You know what I mean? Dennis, sometimes you say the silly... Want me to get that box? No, no, I'll get it. Oh, hello, Don. Well, hello, Jack. Just came over to say goodbye and wish you good luck on your TV show. Oh, thanks, Don. Come on in. Say, Don, you know I have a wonderful idea for a commercial on my television show. I'm going to have the quartet come on, dressed up... Well, now, wait a minute, Jack. Wait a minute. The sportsman won't be able to be with you in New York. They won't. Why not? Well, they're opening at the Chicago Theater on May 18th. Oh, for heaven's sakes, Don. How can they do a thing like that to me?  But, Jack, you booked them. Yes. Well, Don, look at it. Then you'll have to do the commercial. Me? Yes. But, Jack, just standing up doing a commercial on TV isn't funny. I won't get any laughs. Well, maybe you're... Hey, wait a minute, Don. I just thought of a wonderful idea.  Well, of course. How else can you do it? Well, just for a novelty. This'll be great on television.  And when you read the commercial, everybody'll scream. Now, wait a minute, Jack. Nobody's going to laugh at anything that corny, and I'm not going to do it. Don, it'll get laughs, believe me. Now, Don, let's try it. Now, make believe we have a shades lounge here. Now, lie down on the floor.  Don, believe me, I know what I'm doing. It'll be terrific. Now, lie down on the floor. Oh, all right. But do it gently. We don't want to disturb the seismograph at Berkeley. Now, close to your face there. Now, go ahead, Don. Read the commercial. They'll love it. They'll scream. Well, okay. L-S-M-F-T, L-S-M-F-T. Yes, lucky strike means fine demand for it. There's never a rough puff in a lucky strike, and it tastes better than any other cigarette. Yes, folks, it's lucky strike. So round, so firm, so fully packed, so free and easy on the draw. Don, Don, talk louder. The radio waves aren't getting over your stomach. Lucky strike alone gives you an extra major of smoking pleasure.  It wasn't that clever. And listen, Don, I've got a Lulu for the next television show. You're going to read the commercial while standing in quicksand. Of course, you may have to talk fast to finish it, or the last few lines will sound like Sheffield. Now, Don, if you'll excuse me, I've got to finish my packing. Oh, that's all right, Jack. I've got to run along anyway. It's Mother's Day, and I haven't got my mother present yet. Oh. See, I don't know what to buy her. Well, Don, I would suggest flowers or perfume, or maybe a box of fudge. A box of fudge? Hey, that sounds good. There you are, Don. Here, Jack. Thanks. See you along, Don. See you later. Goodbye, Jack. Rochester, put back the perfume and the flowers. He took the fudge. You know, that's really going good today, isn't it? That goes good every day. I wish we could get rid of some of these petunias. We will, we will. Now, let's see. I'll have to... Oh, Mr. Benny. Dennis, are you still here? Yeah, as long as I got my pajamas, I think I'll go upstairs and go to bed. All right, Dennis, you take the lower bunk. Yes, sir. Now, uh, let's see. Oh, if you haven't got bunks in your room, it's just a single bed. Well, he doesn't know the difference. He sleeps under it, you know? Now, come on, Rochester. Let's finish our... There's the doorbell. I'll get it. Oh. Oh, how do you do? How do you do? Are you the little old party who advertised for passengers to New York? Won't you come in? Oh, thank you. Have a seat, Miss, uh, Miss... I'm Miss Lee, Scarlett O'Hara Lee. Scarlett O'Hara... Oh, you must have been named after the heroine and gone with the wind. Yes. You see, my mother was crazy about going with the wind, and I was born while she was in the middle of it. Eating the book? No, watching the picture. Miss Lee, about the trip to New York... Excuse me, but y'all didn't tell me your name. Beanie. I mean Benny. I'm Jack Benny. Jack says something funny. Rochester, what are you doing? Getting back to the trip, but you see, I intend to leave for New York tomorrow. Well, that suits me just fine. Oh, by the way, Miss Lee, what are you going to New York for? Look for a job? Uh-huh, no. I don't need a job. I came into a lot of money when my uncle in Texas passed away. Oh, was your uncle in Texas rich? No, but when they were digging his grave, they struck oil. What a way to go. Chatanooga, Tennessee? Why? Well, that's my hometown. And next week, they're holding their annual fritter-fry-cone-pone-chitlin' the Homney Parson Bake Festival. Yeah, I wish Phil Harris were here to interpret that for me. All I understood was and and festival. Well, I'm very sorry, Miss Lee, but that's a little too far out of the way. You see, we're going to Salt Lake City, Cheyenne, Omaha, and Chicago. Wouldn't you like to go the northern route? If you weren't so cute, I'd slap your face. You're cute, too. Sorry, Mr. Benny, but I... Well, I'm sorry, too. Anyway, it was nice meeting you, Miss Lee. Goodbye. Goodbye. Gee, I'm sorry she's not making the trip with us. You were giving me someone to play gin rummy with. Well, I better finish my... Well, Mr. Benny... Dennis, I thought you went to bed. I did, but I was tossing and turning. I can't fall asleep. Why not?  Back under the bed! Yes, sir. Rochester, when he goes in the room, lock the door so he won't... I'll get it. Yes? How do you do? Are you the party that advertised about a trip to New York? Yes, yes, I am. Oh, well, I'm Mr. Parsons, and this is my wife. How do you do?  Is it a boy or a girl? A boy. Yeah, I thought so. It looks like it from here. Now, sit down, Mrs. Parsons. You must be tired carrying the baby. Thank you very much. Hello, baby.  His eyes are just like mine, aren't they? Are your eyes blue? Bluer than the right shoulder of a left-handed ice man. Now, Mr. Parsons, do you and your wife... Oh, silly me. I forgot to introduce myself. Oh, I know you. You're Jack Benny. I used to see you every Sunday afternoon. You did? Oh, are you in radio? Yes, I'm at Janitor at NBC. Well, how come you're going to New York? CBS bought me. Could we take a look at your car and see if there'd be room for the baby? Well, of course, certainly. It's right out in the driveway there. Right this way, folks. They're driving to New York? Yes, and if you'd like, I'll give you a demonstration. Oh, Rochester! Yes, boss! I want to take these people for a drive. Coming! Now, come on, folks. Jump in. We'll have to. There's no door. It's around on the other side. Come on. Now, go ahead, Rochester. Start the car. Yes, sir. Clugs this morning. I'm not on... Toward Sunset Boulevard. Wait a minute, Mr. Benny. Before you start, I'd like to change places with my wife. Why? I'm afraid she's uncomfortable. And I think I have the softer orange crate. See how nice she runs? The way she takes the bumps? Isn't it nice with the top down? Yes, it is. John! John! That's mine. It blew off. Drive so fast, Rochester. I'll take it a little easier. What was that? Our tail light just fell off. That's all it was. I guess it wasn't on very tight. Well, you see, those are things that we can easily... I'm sick. Aren't you going to stop and pick them up? No! These people are interested in taking the trip with me to New York. Mr. Benny, I don't think we'll be interested in making the trip in this car. Just a minute, Mr. Parsons. You shouldn't back out just because a few minor things went wrong. That could happen to any car. I'm sorry, but I wouldn't risk going another block in this old junk. Old junk? Look, it's not brand new, but they don't make cars like this anymore. Mr. Benny, I'm a janitor and I've swept up better things than this. Oh, yeah? Yeah. Now look, Mr. Parsons. Mr. Benny, I don't want to argue about it. Come on, honey. We'll take the bus. Yes, dear. Some people can never be satisfied. You're right, boss. You'd think that at least give the car a fair trial. A fair trial? Yeah, we... Now let's push it back into the garage. Some golfers like a seven iron and others like a three. But most of them pick lucky strike because LSMFT. Try a pack today because luckies taste better than any other cigarette. Make a smoking joy complete when buying cigarettes. You see, luckies taste better than any other cigarette. Be happy. Friends, when you smoke, you want real enjoyment. And that's exactly why you should switch to lucky strike because luckies taste better than any other cigarette. Yes, every lucky always gives you mildness, smoothness, far better taste than any other cigarette you've ever smoked. And here's why. Fine tobacco and only fine tobacco always gives you the enjoyment of a better tasting cigarette. And LSMFT, lucky strike means fine tobacco. So for complete smoking enjoyment, be happy. Go lucky. Make your next carton lucky strike. You'll find luckies taste better than any other cigarette. Be happy. Go lucky. Go lucky strike today. Remember, luckies taste better than any other cigarette. Happy Mother's Day and good night, folks. Let's be a broadcaster, folks.


Officials from local hospitals say a pregnant mother is amongst eight people who have been wounded in the airstrike in McKelley, the main city in Tigray in northern Ethiopia. The director of emergency services at the city's Aida hospital said the five of them, including the woman who is in the ninth month of pregnancy, were being treated at the hospital. He said the other three were admitted to McKelley Hospital, a central committee member of the Tigray People's Liberation Front. Professor Kindeya Ghebrehiwat said the airstrike took place in the center of the city.


It's day 82 of this 100-day art challenge, and I've been skeptical that it's It's been helpful for mental health specifically my anxiety I'm doing it for and And so one thing I notice is if you're feeling super anxious go make art and then It takes your mind off of it. So short term. It's good, but on day 80 something kind of happened on day 80.  I made art I Think or music. I was just creating stuff and setting up spaces I had I had were working on wood just making stuff making stuff art art art And as time went on I started a business and I made myself a desk job basically and It's been years and years since I've painted So doing this 100-day challenge again on day 80. I Remembered who I was and I'm an artist. I need to make art. I need to make art all the time. It's what I need to do So I'm gonna have to make some big changes in my life and it'll take time, but it can happen Anyways, that's my report Is that time making art every day? And this is so true. We are what we repeatedly do and making art for for 80 days and now I'm an artist What else do I got I had some other note Yeah, I just want to say like you should try painting Just for the bleep of it, you know Remember who you are remember who you are And I've been listening to Mac Miller a lot this album called swimming Okay, thanks for following along on day 100. I want to have everything set up in all the art I I created in one space and and a list of things that We learned for painting every day for a hundred days. I'm gonna give you some art updates This one's almost done. I'm just starting to build this part. I don't know it's gonna be but I'm building something there This one's coming along the face is starting to look starting to see her, you know So it's working and it's foot. We're working right now in this hand. I gotta do This one right here also the face is starting to look okay starting to look okay, like things are in the right place now This one, I don't know. I gotta let it sit for a bit What else and then these ones I found I Started these maybe 20 years ago, and I just added gold to all the squares There's a summer Sometimes you put your art upside down and you can see it with fresh eyes And then fall is in queue because it's almost fall next Sunday. It's fall So summer will go away and fall will be out This is what you see at the eye doctor in the machine. They have up here in Canada Thanks, Tom. All good man Artistry morning. Yeah, Donna. Yeah, so in the eye doctor you look through this machine and you have to focus on this So some people get it and I wrote focus Right there. So these are backdrops just collecting paint. I Wrote this because it seems significant. Remember who you are and then this one I Wrote a bunch of COVID masks and I've been just resonating them to art for some reason So this is a map of the world It's just the first coat of masks, but I Mean the whole frickin world had to wear masks for a Long time. It was terrible Okay, everyone I'll talk to you soon. I hope you have a good rest of the week. I Hope you're making something. Bye. Bye


Imperial College medical student Ravi Amin started feeling symptoms of COVID-19 after just eight days volunteering on the frontline of the pandemic. I got a fever and had some headaches and a little bit of joint pain. Amin is back at work on Wednesday after self-isolating for the past seven days since his fever has subsided English public health officials say he's clear to work even though his cough persists. His housemate James Eaton is also feeling sick.  But he did get it, but fortunately we both had fairly mild symptoms. Amin said he feels safe wearing his personal protective equipment, a mask, gloves, face shields and gown. Talking with his colleagues about his work, he said, helps him deal with the stress. All of the staff in the hospital have just been very, very supportive of one another. Everybody's always asking, you know, are you okay? Are you coping with it well? Amin said he helps in whatever way he can, from feeding and changing patients to monitoring their temperature and taking their blood.  So it's, those things do stick with you. Despite their symptoms, Amin and Eaton will not get tested for the coronavirus. Since they're not in the hospital, they don't get testing priority. Reporting for BU News Service, I'm Chloe Hudson.


The kid is the worst, I think, of the whole movie. How does this kid get cast? I have no idea.  Destroys the entire legacy of the whole thing.  Come on out! It's good packing snow!