A Survey of Mobile Transactions
---
paper_title: A Mobile Transaction Model That Captures Both The Data And Movement Behavior

paper_content:

Unlike distributed transactions, mobile transactions do not originate and end at the same site. The implication of the movement of such transactions is that classical atomicity, concurrency and recovery solutions must be revisited to capture the movement behavior. As an effort in this direction, we define a model of mobile transactions by building on the concepts of split transactions and global transactions in a multidatabase environment. Our view of mobile transactions, called Kangaroo Transactions, incorporates the property that transactions in a mobile computing system hop from one base station to another as the mobile unit moves through cells. Our model is the first to capture this movement behavior as well as the data behavior which reflects the access to data located in databases throughout the static network. The mobile behavior is dynamic and is realized in our model via the use of split operations. The data access behavior is captured by using the idea of global and local transactions in a multidatabase system.
---
paper_title: Data Consistency in Intermittently Connected Distributed Systems

paper_content:

Mobile computing introduces a new form of distributed computation in which communication is most often intermittent, low-bandwidth, or expensive, thus providing only weak connectivity. We present a replication scheme tailored for such environments. Bounded inconsistency is defined by allowing controlled deviation among copies located at weakly connected sites. A dual database interface is proposed that in addition to read and write operations with the usual semantics supports weak read and write operations. In contrast to the usual read and write operations that read consistent values and perform permanent updates, weak operations access only local and potentially inconsistent copies and perform updates that are only conditionally committed. Exploiting weak operations supports disconnected operation since mobile clients can employ them to continue to operate even while disconnected. The extended database interface coupled with bounded inconsistency offers a flexible mechanism for adapting replica consistency to the networking conditions by appropriately balancing the use of weak and normal operations. Adjusting the degree of divergence among copies provides additional support for adaptivity. We present transaction-oriented correctness criteria for the proposed schemes, introduce corresponding serializability-based methods, and outline protocols for their implementation. Then, some practical examples of their applicability are provided. The performance of the scheme is evaluated for a range of networking conditions and varying percentages of weak transactions by using an analytical model developed for this purpose.
---
paper_title: A Framework for Analyzing Mobile Transaction Models

paper_content:

Currently, mobile technology is undergoing a high growth stage, allowing an increasing plethora of mobile devices (handheld PCs, handsets, etc.) to daily access to distributed resources and information. This availability entails the requirement for transactional capabilities adapted to the specific characteristics of the mobile environment without losing the consistency and reliability guarantees of traditional OLTP systems. This paper surveys the definition and extension of transactional models to a mobile environment, starting with an explanation of this environment and a review of transactional systems applied to mobile computing. Afterwards, a framework for analyzing competing mobile models is defined. This framework allows for different constraints to be imposed to the most general "motion independence" requirement. Finally, existing mobile transaction proposals are assessed against the framework and classified, highlighting their relative strengths and weaknesses in different situations.
---
paper_title: The dangers of replication and a solution

paper_content:

Update anywhere-anytime-anyway transactional replication has unstable behavior as the workload scales up: a ten-fold increase in nodes and traffic gives a thousand fold increase in deadlocks or reconciliations. Master copy replication (primary copy) schemes reduce this problem. A simple analytic model demonstrates these results. A new two-tier replication algorithm is proposed that allows mobile (disconnected) applications to propose tentative update transactions that are later applied to a master copy. Commutative update transactions avoid the instability of other replication schemes.
---
paper_title: Transaction processing in mobile computing environment

paper_content:

Distributed systems are expected to support mobile computations executed over a computer network of fixed and mobile hosts. The authors examine the requirements for structuring such mobile computations that access shared data in a database, argue that open-nesting can better facilitate these requirements, and propose an Open-Nested Transaction model in a mobile environment using the notion of Reporting Transactions and Co-Transactions.
---
paper_title: Data Management for Mobile Computing

paper_content:

From the Publisher: ::: The focus of Data Management for Mobile Computing is on the impact of mobile computing on data management beyond the networking level. The purpose is to provide a thorough and cohesive overview of recent advances in wireless and mobile data management. The book is written with a critical attitude. This volume probes the new issues introduced by wireless and mobile access to data and what are both their conceptual and practical consequences. Data Management for Mobile Computing provides a single source for researchers and practitioners who want to keep current on the latest innovations in the field. It can also serve as a textbook for an advanced course on mobile computing or as a companion text for a variety of courses including courses on distributed systems, database management, transaction management, operating or file systems, information retrieval or dissemination, and web computing.
---
paper_title: Principles of Distributed Database Systems

paper_content:

This third edition of a classic textbook can be used to teach at the senior undergraduate and graduate levels. The material concentrates on fundamental theories as well as techniques and algorithms. The advent of the Internet and the World Wide Web, and, more recently, the emergence of cloud computing and streaming data applications, has forced a renewal of interest in distributed and parallel data management, while, at the same time, requiring a rethinking of some of the traditional techniques. This book covers the breadth and depth of this re-emerging field. The coverage consists of two parts. The first part discusses the fundamental principles of distributed data management and includes distribution design, data integration, distributed query processing and optimization, distributed transaction management, and replication. The second part focuses on more advanced topics and includes discussion of parallel database systems, distributed object management, peer-to-peer data management, web data management, data stream systems, and cloud computing. New in this Edition: New chapters, covering database replication, database integration, multidatabase query processing, peer-to-peer data management, and web data management. Coverage of emerging topics such as data streams and cloud computing Extensive revisions and updates based on years of class testing and feedback Ancillary teaching materials are available.
---
paper_title: Submission of transactions from mobile workstations in a cooperative multidatabase processing environment

paper_content:

In a multidatabase environment with mobile computers involved, the nature of computing is such that the user may not wait for the submitted global transaction to complete before disconnecting from the network. In this paper, a basic architectural framework to support transaction management in multidatabase systems is proposed and discussed. A simple message and queuing facility is suggested which provides a common communication and data exchange protocol to effectively manage global transactions submitted by mobile workstations (MWS). The state of global transactions is modelled through the use of transaction sub-queues. The proposed strategy allows an MWS to submit global transactions and then disconnect itself from the network to perform some other tasks, thereby increasing processing parallelism and independence. >
---
paper_title: Supporting semantics-based transaction processing in mobile database applications

paper_content:

Advances in computer and telecommunication technologies have made mobile computing a reality. However, greater mobility implies a more tenuous network connection and a higher rate of disconnection. In order to tolerate disconnections as well as to reduce the delays and cost of wireless communication, it is necessary to support autonomous mobile operations on data shared by stationary hosts. This would allow the part of a computation executing on a mobile host to continue executing while the mobile host is not connected to the network. In this paper, we examine whether object semantics can be exploited to facilitate autonomous and disconnected operation in mobile database applications. We define the class of fragmentable objects which may be split among a number of sites, operated upon independently at each site, and then recombined in a semantically consistent fashion. A number of objects with such characteristics are presented and an implementation of fragmentable stacks is shown and discussed.
---
paper_title: Moflex transaction model for mobile heterogeneous multidatabase systems

paper_content:

Users on mobile hosts can access information from heterogeneous multidatabase systems by mobile transactions via wireless communication. Hence, a mobile transaction model should include not only features for heterogeneous multidatabase systems but also those for a mobile computing environment. In this paper, we propose a mobile transaction model to support the requirements of mobile heterogeneous multidatabase systems. The proposed Moflex (Mobile flexible) transaction model is able to support the management of mobility, heterogeniety and flexibility in the definition and execution of mobile transactions. Hence, the Moflex transaction model can be suitable for mobile heterogeneous multidatabase systems that have low power capability, low bandwidth and a high possibility of communication failure.
---
paper_title: Scalable processing of read-only transactions in broadcast push

paper_content:

Recently, push-based delivery has attracted considerable attention as a means of disseminating information to large client populations in both wired and wireless settings. We address the problem of ensuring the consistency and currency of client read-only transactions in the presence of updates. To this end, additional control information is broadcast. A suite of methods is proposed that vary in the complexity and volume of the control information transmitted and subsequently differ in response times, degrees of concurrency, and space and processing overheads. The proposed methods are combined with caching to improve query latency. The relative advantages of each method are demonstrated through both simulation results and qualitative arguments. Read-only transactions are processed locally at the client without contacting the server and thus the proposed approaches are scalable, i.e., their performance is independent of the number of clients.
---
paper_title: Client-server computing in mobile environments

paper_content:

Recent advances in wireless data networking and portable information appliances have engendered a new paradigm of computing, called mobile computing , in which users carrying portable devices have access to data and information services regardless of their physical location or movement behavior. In the meantime, research addressing information access in mobile environments has proliferated. In this survey, we provide a concrete framework and categorization of the various ways of supporting mobile client-server computing for information access. We examine characteristics of mobility that distinguish mobile client-server computing from its traditional counterpart. We provide a comprehensive analysis of new paradigms and enabler concepts for mobile client-server computing, including mobile-aware adaptation, extended client-server model, and mobile data access. A comparative and detailed review of major research prototypes for mobile information access is also presented.
---
paper_title: Mobile Information Access

paper_content:

Abstract : The ability to access information on demand at any location confers competitive advantage on individuals in an increasingly mobile world. As users become more dependent on this ability, the span of access of data repositories will have to grow. The increasing social acceptance of the home or any other location as a place of work is a further impetus to the development of mechanisms for mobile information access. These considerations imply that data from shared file systems, relational databases, object-oriented databases, and other repositories must be accessible to programs running on mobile computers. For example, a technician servicing a jet engine on a parked aircraft needs access to engineering details of that model of engine as well as past repair records of that specific engine. Similarly, a businessman who is continuing his work on the train home from Manhattan needs access to his business records. Yet another example involves emergency medical response to a case of poisoning: the responding personnel will need rapid access to medical databases describing poison symptoms and antidotes, as well as access to the specific patient s medical records to determine drug sensitivity. This article is a status report on the work being done by my colleagues and myself toward meeting such challenges. It begins by describing a scenario that offers a tantalizing glimpse of the power of mobile information access. The major obstacles on the path toward this vision are then examined. The rest of the article is a summary of research on overcoming these obstacles in the context of the Coda and Odyssey systems.
---
paper_title: Broadcast protocols to support efficient retrieval from databases by mobile users

paper_content:

Mobile computing has the potential for managing information globally. Data management issues in mobile computing have received some attention in recent times, and the design of adaptive braodcast protocols has been posed as an important probllem. Such protocols are employed by database servers to decide on the content of bbroadcasts dynamically, in response to client mobility and demand patterns. In this paper we design such protocols and also propose efficient retrieval strategies that may be employed by clients to download information from broadcasts. The goal is to design cooperative strategies between server and client to provide access to information in such a way as to minimize energy expenditure by clients. We evaluate the performance of our protocols both analytically and through simulation.
---
paper_title: Building information systems for mobile environments

paper_content:

It is expected that in the near future, tens of millions of users will have access to distributed information systems through wireless connections. The technical characteristics of the wireless medium and the resulting mobility of both data resources and data consumers raise new challenging questions regarding the development of information systems appropriate for mobile environments. In this paper, we report on the development of such a system. First, we describe the general architecture of the information system and the main considerations of our design. Then, based on these considerations, we present our system support for maintaining the consistency of replicated data and for providing transaction schemas that account for the frequent but predictable disconnections, the mobility, and the vulnerability of the wireless environment.
---
paper_title: Location dependent data and its management in mobile databases

paper_content:

In traditional ways of managing data, the relationship between the data and the geographical location of the organization it represents, is usually ignored. In wireless computing this property of "location transparency" is in fact often replaced by a "location dependency" property. Furthermore, the mode of issuing queries (the geographical location where the queries originate, the way they are issued, etc.) on such data determines the outcome. Location dependent data is data whose value depends on its location. The objective of the paper is to introduce this topic and spawn further related research.
---
paper_title: A critique of ANSI SQL isolation levels

paper_content:

ANSI SQL-92 [MS, ANSI] defines Isolation Levels in terms of phenomena: Dirty Reads, Non-Repeatable Reads, and Phantoms. This paper shows that these phenomena and the ANSI SQL definitions fail to properly characterize several popular isolation levels, including the standard locking implementations of the levels covered. Ambiguity in the statement of the phenomena is investigated and a more formal statement is arrived at; in addition new phenomena that better characterize isolation types are introduced. Finally, an important multiversion isolation type, called Snapshot Isolation, is defined.
---
paper_title: Principles of transaction-oriented database recovery

paper_content:

In this paper, a terminological framework is provided for describing different transactionoriented recovery schemes for database systems in a conceptual rather than an implementation-dependent way. By introducing the terms materialized database, propagation strategy, and checkpoint, we obtain a means for classifying arbitrary implementations from a unified viewpoint. This is complemented by a classification scheme for logging techniques, which are precisely defined by using the other terms. It is shown that these criteria are related to all relevant questions such as speed and scope of recovery and amount of redundant information required. The primary purpose of this paper, however, is to establish an adequate and precise terminology for a topic in which the confusion of concepts and implementational aspects still imposes a lot of problems.
---
paper_title: Transaction Processing: Concepts and Techniques

paper_content:

From the Publisher: ::: The key to client/server computing. ::: Transaction processing techniques are deeply ingrained in the fields of databases and operating systems and are used to monitor, control and update information in modern computer systems. This book will show you how large, distributed, heterogeneous computer systems can be made to work reliably. Using transactions as a unifying conceptual framework, the authors show how to build high-performance distributed systems and high-availability applications with finite budgets and risk. ::: ::: The authors provide detailed explanations of why various problems occur as well as practical, usable techniques for their solution. Throughout the book, examples and techniques are drawn from the most successful commercial and research systems. Extensive use of compilable C code fragments demonstrates the many transaction processing algorithms presented in the book. The book will be valuable to anyone interested in implementing distributed systems or client/server architectures.
---
paper_title: Concurrency Control and Recovery in Database Systems

paper_content:

This book is an introduction to the design and implementation of concurrency control and recovery mechanisms for transaction management in centralized and distributed database systems. Concurrency control and recovery have become increasingly important as businesses rely more and more heavily on their on-line data processing activities. For high performance, the system must maximize concurrency by multiprogramming transactions. But this can lead to interference between queries and updates, which concurrency control mechanisms must avoid. In addition, a satisfactory recovery system is necessary to ensure that inevitable transaction and database system failures do not corrupt the database.
---
paper_title: The dangers of replication and a solution

paper_content:

Update anywhere-anytime-anyway transactional replication has unstable behavior as the workload scales up: a ten-fold increase in nodes and traffic gives a thousand fold increase in deadlocks or reconciliations. Master copy replication (primary copy) schemes reduce this problem. A simple analytic model demonstrates these results. A new two-tier replication algorithm is proposed that allows mobile (disconnected) applications to propose tentative update transactions that are later applied to a master copy. Commutative update transactions avoid the instability of other replication schemes.
---
paper_title: An algorithm for concurrency control and recovery in replicated distributed databases

paper_content:

In a one-copy distributed database, each data item is stored at exactly one site. In a replicated database, some data items may be stored at multiple sites. The main motivation is improved reliability: by storing important data at multiple sites, the DBS can operate even though some sites have failed. This paper describes an algorithm for handling replicated data, which allows users to operate on data so long as one copy is “available.” A copy is “available” when (i) its site is up, and (ii) the copy is not out-of-date because of an earlier crash. The algorithm handles clean, detectable site failures, but not Byzantine failures or network partitions.
---
paper_title: Data Consistency in Intermittently Connected Distributed Systems

paper_content:

Mobile computing introduces a new form of distributed computation in which communication is most often intermittent, low-bandwidth, or expensive, thus providing only weak connectivity. We present a replication scheme tailored for such environments. Bounded inconsistency is defined by allowing controlled deviation among copies located at weakly connected sites. A dual database interface is proposed that in addition to read and write operations with the usual semantics supports weak read and write operations. In contrast to the usual read and write operations that read consistent values and perform permanent updates, weak operations access only local and potentially inconsistent copies and perform updates that are only conditionally committed. Exploiting weak operations supports disconnected operation since mobile clients can employ them to continue to operate even while disconnected. The extended database interface coupled with bounded inconsistency offers a flexible mechanism for adapting replica consistency to the networking conditions by appropriately balancing the use of weak and normal operations. Adjusting the degree of divergence among copies provides additional support for adaptivity. We present transaction-oriented correctness criteria for the proposed schemes, introduce corresponding serializability-based methods, and outline protocols for their implementation. Then, some practical examples of their applicability are provided. The performance of the scheme is evaluated for a range of networking conditions and varying percentages of weak transactions by using an analytical model developed for this purpose.
---
paper_title: Maintaining consistency of data in mobile distributed environments

paper_content:

To deal with the frequent, foreseeable and variable disconnections that occur in a mobile environment, we introduce a flexible, two-level consistency model. Semantically related or closely located data are grouped together to form a cluster. While all data inside a cluster are mutually consistent, degrees of inconsistency are allowed among data at different clusters. To take advantage of the predictability of disconnections, and to accommodate mobility, the cluster configuration is dynamic. We allow transactions to exhibit certain degrees of tolerance for inconsistencies by introducing strict and weak operations. Weak operations are operations that can be executed under weaker consistency requirements. We define correctness criteria for schedules that involve weak operations and compare them with traditional serializability criteria. Finally, we argue that our model is appropriate for a variety of other environments including very large databases and multidatabases.
---
paper_title: An algorithm for concurrency control and recovery in replicated distributed databases

paper_content:

In a one-copy distributed database, each data item is stored at exactly one site. In a replicated database, some data items may be stored at multiple sites. The main motivation is improved reliability: by storing important data at multiple sites, the DBS can operate even though some sites have failed. This paper describes an algorithm for handling replicated data, which allows users to operate on data so long as one copy is “available.” A copy is “available” when (i) its site is up, and (ii) the copy is not out-of-date because of an earlier crash. The algorithm handles clean, detectable site failures, but not Byzantine failures or network partitions.
---
paper_title: The dangers of replication and a solution

paper_content:

Update anywhere-anytime-anyway transactional replication has unstable behavior as the workload scales up: a ten-fold increase in nodes and traffic gives a thousand fold increase in deadlocks or reconciliations. Master copy replication (primary copy) schemes reduce this problem. A simple analytic model demonstrates these results. A new two-tier replication algorithm is proposed that allows mobile (disconnected) applications to propose tentative update transactions that are later applied to a master copy. Commutative update transactions avoid the instability of other replication schemes.
---
paper_title: HiCoMo: High Commit Mobile Transactions

paper_content:

We introduce a new mobile transaction model applicable to decisionmaking applications over aggregate data warehoused on mobile hosts. The model allows the aggregate data to be updated in disconnection mode, while guaranteeing a very high rate of commitment on reconnection. We name such transactions High Commit Mobile Transactions, or HiCoMo. At reconnectiontime, HiCoMo's are analyzed and several base (fixed network) transactions are generated in order to bring the same effect upon the base tables from which the aggregates are derived. In this paper, we provide a formal definition for the concepts related to HiCoMo's, and a transformation algorithm that is used to analyze them and generate base transactions. We provide a simple example scenario to demonstrate the usefulness of this transaction model. Finally, we compare the commit behavior of HiCoMo's to that of the two-tier model using simulation and a mobile transaction benchmark drawn from an inventory application domain.
---
paper_title: Improving data consistency in mobile computing using isolation-only transactions

paper_content:

Disconnected operation is an important technique for providing mobile access to shared data in distributed file systems. However, data inconsistency resulting from partitioned sharing remains a serious concern. This paper presents a new mechanism called isolation-only transaction (IOT) that uses serializability constraints to automatically detect read/write conflicts. The IOT consistency model provides a set of options for automatic and manual conflict resolution. In addition, application-specific knowledge can be incorporated to detect and resolve conflicts. To preserve upward Unix compatibility, the IOT mechanism is provided as an optional file system facility and its flexible interfaces allow any existing Unix application to be executed as an IOT. This paper describes high-level system design and implementation and concludes with related work and current status.
---
paper_title: Isolation-only transactions for mobile computing

paper_content:

The Unix File System(UFS) has historically offered a shared-memory consistency model. The lack of concurrency control makes this model susceptible to read/write conflicts, i.e., unexpected read/write sharing between two different processes. For example, the update of a header file by one user while another user is performing a long-runningmake can cause inconsistencies in the compilation results. In practice, read/write conflicts are rare for two reasons. First, the window of vulnerability is relatively small because read/write conflicts only occur when the executions of two processes overlap. Second, they are often prevented via explicit user-level coordination.
---
paper_title: Transaction processing in mobile computing environment

paper_content:

Distributed systems are expected to support mobile computations executed over a computer network of fixed and mobile hosts. The authors examine the requirements for structuring such mobile computations that access shared data in a database, argue that open-nesting can better facilitate these requirements, and propose an Open-Nested Transaction model in a mobile environment using the notion of Reporting Transactions and Co-Transactions.
---
paper_title: PRO-MOTION: management of mobile transactions

paper_content:

In order to provide data consistency in the presence of failures and concurrency, database methods will continue to be important to the processing of shared information in a mobile computing environment. It is important, therefore, that we develop transaction processing systems that accommodate the limitations of mobile computing, such as frequent disconnection, limited battery life, low-bandwidth communication and reduced storage capacity, so that we can migrate existing database applications to mobile environments. In this paper, motivated by these needs, we propose a mobile transaction processing system that supports disconnected transaction processing in a mobile client-server environment. The proposed system employs compacts, which encapsulate access methods, state informationand consistency constraints, to allow for local management of database transactions. Finally, we discuss the basic infrastructure needed to support this transaction processing system.
---
paper_title: Using semantic knowledge for transaction processing in a distributed database

paper_content:

This paper investigates how the semantic knowledge of an application can be used in a distributed database to process transactions efficiently and to avoid some of the delays associated with failures. The main idea is to allow nonserializable schedules which preserve consistency and which are acceptable to the system users. To produce such schedules, the transaction processing mechanism receives semantic information from the users in the form of transaction semantic types, a division of transactions into steps, compatibility sets, and countersteps. Using these notions, we propose a mechanism which allows users to exploit their semantic knowledge in an organized fashion. The strengths and weaknesses of this approach are discussed.
---
paper_title: Synthesis of extended transaction models using ACTA

paper_content:

ACTA is a comprehensive transaction framework that facilitates the formal description of properties of extended transaction models. Specifically, using ACTA, one can specify and reason about (1) the effects of transactions on objects and (2) the interactions between transactions. This article presents ACTA as a tool for the synthesis of extended transaction models , one which supports the development and analysis of new extended transaction models in a systematic manner. Here, this is demonstrated by deriving new transaction definitions (1) by modifying the specifications of existing transaction models, (2) by combining the specifications of existing models, and (3) by starting from first principles. To exemplify the first, new models are synthesized from atomic transactions and join transactions . To illustrate the second, we synthesize a model that combines aspect of the nested - and split-transaction models. We demonstrate the latter by deriving the specification of an open-nested-transaction model from high-level requirements.
---
paper_title: Transaction processing in mobile computing environment

paper_content:

Distributed systems are expected to support mobile computations executed over a computer network of fixed and mobile hosts. The authors examine the requirements for structuring such mobile computations that access shared data in a database, argue that open-nesting can better facilitate these requirements, and propose an Open-Nested Transaction model in a mobile environment using the notion of Reporting Transactions and Co-Transactions.
---
paper_title: Split-Transactions for Open-Ended Activities

paper_content:

Open-ended activities such as CAD/CAM, VLSI layout and software development require consistent concurrent access and fault tolerance associated with database transactions, but their uncertain duration, uncertain developments during execution and long interactions with other concurrent activities break traditional transaction atomicity boundaries. We propose splittransaction as a new database operation that solves the above problems by permitting transactions to commit data that will not change. Thus an open-ended activity can release the committed data and serialize interactions with other concurrent activities through the committed data.
---
paper_title: Supporting semantics-based transaction processing in mobile database applications

paper_content:

Advances in computer and telecommunication technologies have made mobile computing a reality. However, greater mobility implies a more tenuous network connection and a higher rate of disconnection. In order to tolerate disconnections as well as to reduce the delays and cost of wireless communication, it is necessary to support autonomous mobile operations on data shared by stationary hosts. This would allow the part of a computation executing on a mobile host to continue executing while the mobile host is not connected to the network. In this paper, we examine whether object semantics can be exploited to facilitate autonomous and disconnected operation in mobile database applications. We define the class of fragmentable objects which may be split among a number of sites, operated upon independently at each site, and then recombined in a semantically consistent fashion. A number of objects with such characteristics are presented and an implementation of fragmentable stacks is shown and discussed.
---
paper_title: A Mobile Transaction Model That Captures Both The Data And Movement Behavior

paper_content:

Unlike distributed transactions, mobile transactions do not originate and end at the same site. The implication of the movement of such transactions is that classical atomicity, concurrency and recovery solutions must be revisited to capture the movement behavior. As an effort in this direction, we define a model of mobile transactions by building on the concepts of split transactions and global transactions in a multidatabase environment. Our view of mobile transactions, called Kangaroo Transactions, incorporates the property that transactions in a mobile computing system hop from one base station to another as the mobile unit moves through cells. Our model is the first to capture this movement behavior as well as the data behavior which reflects the access to data located in databases throughout the static network. The mobile behavior is dynamic and is realized in our model via the use of split operations. The data access behavior is captured by using the idea of global and local transactions in a multidatabase system.
---
paper_title: Database transaction models for advanced applications

paper_content:

1 Transaction Management in Database Systems 2 Introduction to Advanced Transaction Models 3 A Cooperative Transaction Model for Design Databases 4 A Flexible Framework for Transaction Management in Engineering Environments 5 A Transaction Model for Active Distributed Object Systems 6 A Transaction Model for an Open Publication Environment 7 The ConTract Model 8 Dynamic Restructuring of Transactions 9 Multidatabase Transaction and Query Processing in Logic 10 ACTA: The Saga Continues 11 A Transaction Manager Development Facility for Non Standard Database Systems 12 The S-Transaction Model 13 Concepts and Applications of Multilevel Transactions and Open Nested Transactions 14 Using Polytransactions to Manage Interdependent Data
---
paper_title: Split-Transactions for Open-Ended Activities

paper_content:

Open-ended activities such as CAD/CAM, VLSI layout and software development require consistent concurrent access and fault tolerance associated with database transactions, but their uncertain duration, uncertain developments during execution and long interactions with other concurrent activities break traditional transaction atomicity boundaries. We propose splittransaction as a new database operation that solves the above problems by permitting transactions to commit data that will not change. Thus an open-ended activity can release the committed data and serialize interactions with other concurrent activities through the committed data.
---
paper_title: Submission of transactions from mobile workstations in a cooperative multidatabase processing environment

paper_content:

In a multidatabase environment with mobile computers involved, the nature of computing is such that the user may not wait for the submitted global transaction to complete before disconnecting from the network. In this paper, a basic architectural framework to support transaction management in multidatabase systems is proposed and discussed. A simple message and queuing facility is suggested which provides a common communication and data exchange protocol to effectively manage global transactions submitted by mobile workstations (MWS). The state of global transactions is modelled through the use of transaction sub-queues. The proposed strategy allows an MWS to submit global transactions and then disconnect itself from the network to perform some other tasks, thereby increasing processing parallelism and independence. >
---
paper_title: Location dependent data and its management in mobile databases

paper_content:

In traditional ways of managing data, the relationship between the data and the geographical location of the organization it represents, is usually ignored. In wireless computing this property of "location transparency" is in fact often replaced by a "location dependency" property. Furthermore, the mode of issuing queries (the geographical location where the queries originate, the way they are issued, etc.) on such data determines the outcome. Location dependent data is data whose value depends on its location. The objective of the paper is to introduce this topic and spawn further related research.
---
paper_title: A Multidatabase Transaction Model for InterBase

paper_content:

The management of multidatabase transactions presents new and interesting challenges, due mainly to the requirement of the autonomy of local database systems. In this paper, we present an extended transaction model which provides the following features useful in a multidatabase environment: (1) It allows the composition of flexi.ble transactions which can tolerate failures of individual sub transactions by taking advantage of the fact that a given function can frequently be accomplished by more than one database system; (2) It supports the concept of mixed transactions allowing compensatable and non-compensatable subtransactions to coexist within a single global transaction; and (3) It incorporates the concept of time jn both the subtransaction and global transaction processing, thus allowing more flexibility in transaction scheduling. We formally define the extended transaction model and discuss its transaction scheduling mechanism.
---
paper_title: Moflex transaction model for mobile heterogeneous multidatabase systems

paper_content:

Users on mobile hosts can access information from heterogeneous multidatabase systems by mobile transactions via wireless communication. Hence, a mobile transaction model should include not only features for heterogeneous multidatabase systems but also those for a mobile computing environment. In this paper, we propose a mobile transaction model to support the requirements of mobile heterogeneous multidatabase systems. The proposed Moflex (Mobile flexible) transaction model is able to support the management of mobility, heterogeniety and flexibility in the definition and execution of mobile transactions. Hence, the Moflex transaction model can be suitable for mobile heterogeneous multidatabase systems that have low power capability, low bandwidth and a high possibility of communication failure.
---
paper_title: A Pre-Serialization Transaction Management Technique for Mobile Multidatabases

paper_content:

Rapid advances in hardware and wireless communication technology have made the concept of mobile computing a reality. Thus, evolving database technology needs to address the requirements of the future mobile user. The frequent disconnection and migration of the mobile user violate underlying presumptions about connectivity that exist in wired database systems and introduce new issues that affect transaction management. In this paper, we present the Pre-Serialization (PS) transaction management technique for the mobile multidatabase environment. This technique addresses disconnection and migration and enforces a range of atomicity and isolation criteria. We also develop an analytical model to compare the performance of the PS technique to that of the Kangaroo model.
---
paper_title: PicoDBMS: Scaling down database techniques for the smartcard

paper_content:

Smartcards are the most secure portable computing device today. They have been used successfully in applications involving money, and proprietary and personal data (such as banking, healthcare, insurance, etc.). As smartcards get more powerful (with 32-bit CPU and more than 1 MB of stable memory in the next versions) and become multi-application, the need for database management arises. However, smartcards have severe hardware limitations (very slow write, very little RAM, constrained stable memory, no autonomy, etc.) which make traditional database technology irrelevant. The major problem is scaling down database techniques so they perform well under these limitations. In this paper, we give an in-depth analysis of this problem and propose a PicoDBMS solution based on highly compact data structures, query execution without RAM, and specific techniques for atomicity and durability. We show the effectiveness of our techniques through performance evaluation.
---
paper_title: GnatDb: A Small-Footprint, Secure Database System

paper_content:

This paper describes GnatDb, which is an embedded database system that provides protection against both accidental and malicious corruption of data. GnatDb is designed to run on a wide range of appliances, some of which have very limited resources. Therefore, its design is heavily driven by the need to reduce resource consumption. GnatDb employs atomic and durable updates to protect the data against accidental corruption. It prevents malicious corruption of the data using standard cryptographic techniques that leverage the underlying log-structured storage model. We show that the total memory consumption of GnatDb, which includes the code footprint, the stack and the heap, does not exceed 11 KB, while its performance on a typical appliance platform remains at an acceptable level.
---
paper_title: Principles of transaction-oriented database recovery

paper_content:

In this paper, a terminological framework is provided for describing different transactionoriented recovery schemes for database systems in a conceptual rather than an implementation-dependent way. By introducing the terms materialized database, propagation strategy, and checkpoint, we obtain a means for classifying arbitrary implementations from a unified viewpoint. This is complemented by a classification scheme for logging techniques, which are precisely defined by using the other terms. It is shown that these criteria are related to all relevant questions such as speed and scope of recovery and amount of redundant information required. The primary purpose of this paper, however, is to establish an adequate and precise terminology for a topic in which the confusion of concepts and implementational aspects still imposes a lot of problems.
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paper_title: TCOT - A Timeout-based Mobile Transaction Commitment Protocol

paper_content:

We present a transaction commit protocol, "Transaction Commit On Timeout (TCOT)," based on a "timeout" approach for Mobile Database Systems (MDS), which can be universally used to reach a final transaction termination decision (e.g., commit, abort, etc.) in any message-oriented system. Particularly suited for a wireless environment, a timeout mechanism is the only way to minimize the impact of the slow and unreliable wireless link. We compare TCOT to a modified version of 2PC to show its superiority based on commit time.
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paper_title: PicoDBMS: Scaling down database techniques for the smartcard

paper_content:

Smartcards are the most secure portable computing device today. They have been used successfully in applications involving money, and proprietary and personal data (such as banking, healthcare, insurance, etc.). As smartcards get more powerful (with 32-bit CPU and more than 1 MB of stable memory in the next versions) and become multi-application, the need for database management arises. However, smartcards have severe hardware limitations (very slow write, very little RAM, constrained stable memory, no autonomy, etc.) which make traditional database technology irrelevant. The major problem is scaling down database techniques so they perform well under these limitations. In this paper, we give an in-depth analysis of this problem and propose a PicoDBMS solution based on highly compact data structures, query execution without RAM, and specific techniques for atomicity and durability. We show the effectiveness of our techniques through performance evaluation.
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paper_title: TCOT - A Timeout-based Mobile Transaction Commitment Protocol

paper_content:

We present a transaction commit protocol, "Transaction Commit On Timeout (TCOT)," based on a "timeout" approach for Mobile Database Systems (MDS), which can be universally used to reach a final transaction termination decision (e.g., commit, abort, etc.) in any message-oriented system. Particularly suited for a wireless environment, a timeout mechanism is the only way to minimize the impact of the slow and unreliable wireless link. We compare TCOT to a modified version of 2PC to show its superiority based on commit time.
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paper_title: A Timeout-Based Mobile Transaction Commitment Protocol

paper_content:

We investigate transaction commit in Mobile Database Systems (MDS) and develop a commitment protocol based on "timeout" approach. Timeout approach is universally used to reach a decision as a last option in all message oriented systems. With this approach we have minimized the use of wireless message cost in commiting transactions.
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paper_title: A critique of ANSI SQL isolation levels

paper_content:

ANSI SQL-92 [MS, ANSI] defines Isolation Levels in terms of phenomena: Dirty Reads, Non-Repeatable Reads, and Phantoms. This paper shows that these phenomena and the ANSI SQL definitions fail to properly characterize several popular isolation levels, including the standard locking implementations of the levels covered. Ambiguity in the statement of the phenomena is investigated and a more formal statement is arrived at; in addition new phenomena that better characterize isolation types are introduced. Finally, an important multiversion isolation type, called Snapshot Isolation, is defined.
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paper_title: On Optimistic Methods For Concurrency Control

paper_content:

Most current approaches to concurrency control in database systems rely on locking of data objects as a control mechanism. In this paper, two families of non-locking concurrency controls are presented. The methods used are "optimistic" in the sense that they rely mainly on transaction backup as a control mechanism, "hoping" that conflicts between transactions will not occur. Applications where these methods should be more efficient than locking are discussed.
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paper_title: Principles of Distributed Database Systems

paper_content:

This third edition of a classic textbook can be used to teach at the senior undergraduate and graduate levels. The material concentrates on fundamental theories as well as techniques and algorithms. The advent of the Internet and the World Wide Web, and, more recently, the emergence of cloud computing and streaming data applications, has forced a renewal of interest in distributed and parallel data management, while, at the same time, requiring a rethinking of some of the traditional techniques. This book covers the breadth and depth of this re-emerging field. The coverage consists of two parts. The first part discusses the fundamental principles of distributed data management and includes distribution design, data integration, distributed query processing and optimization, distributed transaction management, and replication. The second part focuses on more advanced topics and includes discussion of parallel database systems, distributed object management, peer-to-peer data management, web data management, data stream systems, and cloud computing. New in this Edition: New chapters, covering database replication, database integration, multidatabase query processing, peer-to-peer data management, and web data management. Coverage of emerging topics such as data streams and cloud computing Extensive revisions and updates based on years of class testing and feedback Ancillary teaching materials are available.
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paper_title: An algorithm for concurrency control and recovery in replicated distributed databases

paper_content:

In a one-copy distributed database, each data item is stored at exactly one site. In a replicated database, some data items may be stored at multiple sites. The main motivation is improved reliability: by storing important data at multiple sites, the DBS can operate even though some sites have failed. This paper describes an algorithm for handling replicated data, which allows users to operate on data so long as one copy is “available.” A copy is “available” when (i) its site is up, and (ii) the copy is not out-of-date because of an earlier crash. The algorithm handles clean, detectable site failures, but not Byzantine failures or network partitions.
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paper_title: Concurrency Control and Recovery in Database Systems

paper_content:

This book is an introduction to the design and implementation of concurrency control and recovery mechanisms for transaction management in centralized and distributed database systems. Concurrency control and recovery have become increasingly important as businesses rely more and more heavily on their on-line data processing activities. For high performance, the system must maximize concurrency by multiprogramming transactions. But this can lead to interference between queries and updates, which concurrency control mechanisms must avoid. In addition, a satisfactory recovery system is necessary to ensure that inevitable transaction and database system failures do not corrupt the database.
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paper_title: Distributed lock management for mobile transactions

paper_content:

We present a new lock management scheme which allows a read unlock for an item to be executed at any copy site of that item; the site may be different from the copy site on which the read lock is set. The scheme utilizes the replicated copies of data items to reduce the message costs incurred by the mobility of the transaction host. We demonstrate this idea in an optimistic locking algorithm called O2PL-MT (Optimistic Two Phase Locking for Mobile Transactions). Like its counterpart algorithm O2PL (Optimistic Two Phase Locking), O2PL-MT grants read locks immediately on demand and defers write locks until the commitment time. However, O2PL-MT requires the transmission of fewer messages than O2PL in a mobile environment in which data items are replicated.
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paper_title: A taxonomy of correctness criteria in database applications

paper_content:

Whereas serializability captures database consistency requirements and transaction correctness properties via a single notion, recent research has attempted to come up with correctness criteria that view these two types of requirements independently. The search for more flexible correctness criteria is partily motivated by the introduction of new transaction models that extend the traditional atomic transaction model. These extensions came about because the atomic transaction model in conjunction with serializability is found to be very constraining when used in advanced applications (e.g., design databases) that function in distributed, cooperative, and heterogeneous environments.In this article we develop a taxonomy of various correctness criteria that focus on database consistency requirements and transaction correctness properties from the viewpoint of what the different dimensions of these two are. This taxonomy allows us to categorize correctness criteria that have been proposed in the literature. To help in this categorization, we have applied a uniform specification technique, based on ACTA, to express the various criteria. Such a categorization helps shed light on the similarities and differences between different criteria and places them in perspective.
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paper_title: Flexible Integration of Optimistic and Pessimistic Concurrency Control in Mobile Environments

paper_content:

Limited execution capability, weak connections with the fixed network, frequent disconnections, and mobility dictate naturally an optimistic mode for transaction execution at mobile hosts (MH): the relevant computation is performed at MHs with cached data to provide quick response to the user, but the execution is validated against concurrent transactions and ACID properties maintained at the fixed network. Some of the proposals in the literature to reduce the likelihood of invalidation and thus increase the meaningfulness of computation at MH are: (i) If the validation fails, the transaction could be re-executed and accepted even when the results differ from the original ones but within certain limits; (ii) Validation/re-execution idea can be extended to several intermediate stages and the computation at MH adjusted with respect to changes in the database state at the fixed network. In this paper, we strengthen the computation at MH further by facilitating partial guarantee against invalidation. This is accomplished by switching the computation to a pessimistic mode. Varying degrees of pessimism are provided. They balance the guarantee against its effect on other transactions' executions.
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paper_title: PicoDBMS: Scaling down database techniques for the smartcard

paper_content:

Smartcards are the most secure portable computing device today. They have been used successfully in applications involving money, and proprietary and personal data (such as banking, healthcare, insurance, etc.). As smartcards get more powerful (with 32-bit CPU and more than 1 MB of stable memory in the next versions) and become multi-application, the need for database management arises. However, smartcards have severe hardware limitations (very slow write, very little RAM, constrained stable memory, no autonomy, etc.) which make traditional database technology irrelevant. The major problem is scaling down database techniques so they perform well under these limitations. In this paper, we give an in-depth analysis of this problem and propose a PicoDBMS solution based on highly compact data structures, query execution without RAM, and specific techniques for atomicity and durability. We show the effectiveness of our techniques through performance evaluation.
---
paper_title: An algorithm for concurrency control and recovery in replicated distributed databases

paper_content:

In a one-copy distributed database, each data item is stored at exactly one site. In a replicated database, some data items may be stored at multiple sites. The main motivation is improved reliability: by storing important data at multiple sites, the DBS can operate even though some sites have failed. This paper describes an algorithm for handling replicated data, which allows users to operate on data so long as one copy is “available.” A copy is “available” when (i) its site is up, and (ii) the copy is not out-of-date because of an earlier crash. The algorithm handles clean, detectable site failures, but not Byzantine failures or network partitions.
---
paper_title: Disconnected operation in the Coda file system

paper_content:

Disconnected operation is a mode of operation that enables a client to continue accessing critical data during temporary failures of a shared data repository. An important, though not exclusive, application of disconnected operation is in supporting portable computers. In this paper, we show that disconnected operation is feasible, efficient and usable by describing its design and implementation in the Coda File System. The central idea behind our work is that caching of data, now widely used for performance, can also be exploited to improve availability.
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paper_title: Using tickets to enforce the serializability of multidatabase transactions

paper_content:

To enforce global serializability in a multidatabase environment the multidatabase transaction manager must take into account the indirect (transitive) conflicts between multidatabase transactions caused by local transactions. Such conflicts are difficult to resolve because the behavior or even the existence of local transactions is not known to the multidatabase system. To overcome these difficulties, we propose to incorporate additional data manipulation operations in the subtransactions of each multidatabase transaction. We show that if these operations create direct conflicts between subtransactions at each participating local database system, indirect conflicts can be resolved even if the multidatabase system is not aware of their existence. Based on this approach, we introduce optimistic and conservative multidatabase transaction management methods that require the local database systems to ensure only local serializability. The proposed methods do not violate the autonomy of the local database systems and guarantee global serializability by preventing multidatabase transactions from being serialized in different ways at the participating database systems. Refinements of these methods are also proposed for multidatabase environments where the participating database systems allow schedules that are cascadeless or transactions have analogous execution and serialization orders. In particular, we show that forced local conflicts can be eliminated in rigorous local systems, local cascadelessness simplifies the design of a global scheduler, and that local strictness offers no significant advantages over cascadelessness. >
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paper_title: Location dependent data and its management in mobile databases

paper_content:

In traditional ways of managing data, the relationship between the data and the geographical location of the organization it represents, is usually ignored. In wireless computing this property of "location transparency" is in fact often replaced by a "location dependency" property. Furthermore, the mode of issuing queries (the geographical location where the queries originate, the way they are issued, etc.) on such data determines the outcome. Location dependent data is data whose value depends on its location. The objective of the paper is to introduce this topic and spawn further related research.
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paper_title: Defining an Adaptable Mobile Transaction Service

paper_content:

Mobile environments are characterized by frequent variations in connection and bandwidth rates as well as by restrained resources on portable devices. This variability complicates data management and in particular, transaction execution. We consider that to deal with environment variability it is necessary to be adaptable. This paper proposes both a Mobile Transaction Service (MTS) and an Adaptable Mobile Transaction model (AMT) which offer environment awareness and transaction execution adaptability. The MTS is a middleware that besides coordinating the execution of mobile transactions, supports mobile environment awareness. The AMT allows the description of different semantical equivalent ways of executing mobile transactions. Thus, depending on the environment mobile transactions will be executed.
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Title: A Survey of Mobile Transactions
Section 1: Introduction
Description 1: This section introduces the prevalence of mobile devices and networks, discusses the need for adapted transaction models, and outlines the structure of the paper.

Section 2: Mobile transaction context
Description 2: This section discusses features related to mobile transactions, including system architecture, operation modes, execution models, and the limitations of traditional techniques in mobile contexts.

Section 3: Architectural context
Description 3: This section explains the client-server architecture in mobile environments and introduces different architectural approaches for transaction execution.

Section 4: Operation modes of a mobile host
Description 4: This section presents different operation modes for mobile hosts under varying connectivity conditions, such as strong and weak connections, disconnected and doze modes.

Section 5: Execution models
Description 5: This section defines various execution models for mobile transactions, ranging from complete execution on the wired network to distributed execution among multiple mobile hosts.

Section 6: Unsuitability of classical ACID techniques
Description 6: This section examines why classical ACID properties are challenging to maintain in mobile environments and discusses alternatives like commit protocols and concurrency control mechanisms.

Section 7: Mobile transaction proposals
Description 7: This section introduces and analyzes major research projects that propose transaction processing models adapted to mobile environments.

Section 8: Commercial products
Description 8: This section describes some commercial products that offer database solutions for mobile environments, including their capabilities and limitations.

Section 9: Summary and discussion
Description 9: This section summarizes and discusses the findings from the research projects and commercial products, identifying trends and common techniques.

Section 10: Ensuring ACID properties for mobile transactions
Description 10: This section presents approaches to ensure ACID properties in mobile transactions, discussing commit protocols, semantic information, isolation, durability, and logging.

Section 11: Movement and disconnection management
Description 11: This section examines how existing models handle mobile host movement and disconnections, comparing different strategies and their effectiveness.

Section 12: Conclusions and research directions
Description 12: This section concludes the paper, highlighting the importance of mobile transactions, discussing the challenges in maintaining ACID properties, and suggesting areas for future research.