A survey of transactional issues for Web Service composition and recovery
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paper_title: Service-Oriented Computing: Semantics, Processes, Agents

paper_content:

About the Authors.Preface.Note to the Reader.Acknowledgments.Figures.Tables.Listings.I Basics.1. Computing with Services.2. Basic Standards for Web Services.3. Programming Web Services.4. Enterprise Architectures.5. Principles of Service-Oriented Computing.II Description.6. Modeling and Representation.7. Resource Description Framework.8. Web Ontology Language.9. Ontology Management.III Engagement.10. Execution Models.11. Transaction Concepts.12. Coordination Frameworks for Web Services.13. Process Specifications.14. Formal Specification and Enactment.IV Collaboration.15. Agents.16. Multiagent Systems.17. Organizations.18. Communication.V Solutions.19. Semantic Service Solutions.20. Social Service Selection.21. Economic Service Selection.VI Engineering.22. Building SOC Applications.23. Service Management.24. Security.VII Directions.25. Challenge and Extensions.VIII Appendices.Appendix A: XML and XML Schema.Appendix B: URI, URN, URL and UUID.Appendix C: XML Namespace Abbreviations.Glossary.About the Authors.Bibliography.Index.
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paper_title: Fundamentals of Database Systems

paper_content:

From the Publisher: ::: Fundamentals of Database Systems combines clear explanations of theory and design, broad coverage of models and real systems, and excellent examples with up-to-date introductions to modern database technologies. This edition is completely revised and updated, and reflects the latest trends in technological and application development. Professors Elmasri and Navathe focus on the relational model and include coverage of recent object-oriented developments. They also address advanced modeling and system enhancements in the areas of active databases, temporal and spatial databases, and multimedia information systems. This edition also surveys the latest application areas of data warehousing, data mining, web databases, digital libraries, GIS, and genome databases. New to the Third Edition ::: Reorganized material on data modeling to clearly separate entity relationship modeling, extended entity relationship modeling, and object-oriented modeling Expanded coverage of the object-oriented and object/relational approach to data management, including ODMG and SQL3 Uses examples from real database systems including OracleTM and Microsoft AccessAE Includes discussion of decision support applications of data warehousing and data mining, as well as emerging technologies of web databases, multimedia, and mobile databases Covers advanced modeling in the areas of active, temporal, and spatial databases Provides coverage of issues of physical database tuning Discusses current database application areas of GIS, genome, and digital libraries
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paper_title: Workflow and Process Automation: Concepts and Technology

paper_content:

Preface. 1. Introduction. 2. Process Technology. 3. Workflow Technology. 4. Transactional Aspects of Workflows. 5. Ongoing Research in Workflow and Process Automation. 6. State of the Industry. References. Index.
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paper_title: Principles and realization strategies of multilevel transaction management

paper_content:

One of the demands of database system transaction management is to achieve a high degree of concurrency by taking into consideration the semantics of high-level operations. On the other hand, the implementation of such operations must pay attention to conflicts on the storage representation levels below. To meet these requirements in a layered architecture, we propose a multilevel transaction management utilizing layer-specific semantics. Based on the theoretical notion of multilevel serializability, a family of concurrency control strategies is developed. Suitable recovery protocols are investigated for aborting single transactions and for restarting the system after a crash. The choice of levels involved in a multilevel transaction strategy reveals an inherent trade-off between increased concurrency and growing recovery costs. A series of measurements has been performed in order to compare several strategies. Preliminary results indicate considerable performance gains of the multilevel transaction approach.
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paper_title: Nested Transactions An Approach To Reliable Distributed Computing

paper_content:

Thank you for reading nested transactions an approach to reliable distributed computing. Maybe you have knowledge that, people have search hundreds times for their chosen novels like this nested transactions an approach to reliable distributed computing, but end up in harmful downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they cope with some malicious virus inside their laptop.
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paper_title: Transaction Management Support for Cooperative Applications

paper_content:

Foreword. 1. Introduction W. Klas, et al. 2. The TransCoop Paradigm J. Veijalainen, et al. 3. Transaction Models in Cooperative Work - An Overview J. Veijalainen, et al. 4. Application Requirements T. Tesch, et al. 5. The TransCoop Architecture A. Lehtola, et al. 6. The TransCoop Specification Environment F.J. Faase, et al. 7. The TransCoop Transaction Model J. Klingemann, et al. 8. The TransCoop Demonstrator System J. Klingemann, S. Even. 9. Conclusions S. Even, et al. References. Index.
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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
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paper_title: Log-Based Recovery for Nested Transactions

paper_content:

Techniques similar to shadow pages have been suggested for use in rollback and crash recovery for nested transactions. However, undo/redo log methods have not been presented, though undo/redo logs are widely used for transaction recovery, and perhaps preferable to shadow methods. We develop a scheme of log-based recovery for nested transactions. The resulting design is promising because it requires a relatively small number of extensions to a similar scheme of recovery for single-level transactions.
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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.
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paper_title: The Workflow Activity Model WAMO

paper_content:

Workflow technology has not yet lived up to its expectations not only because of social problems but also because of technical problems, like inflexible and rigid process specification and execution mechanisms and insufficient possibilities to handle exceptions. The aim of this paper is to present a workflow model which significantly facilitates the design and reliable management of complex business processes supported by an automatic mechanism to handle exceptions. The strength of the model is its simplicity and the application independent transaction facility (advanced control mechanism for workflow units) which guarantees reliable execution of workflow activities.
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paper_title: The Mentor project: steps towards enterprise-wide workflow management

paper_content:

Enterprise-wide workflow management where workflows may span multiple organizational units require particular consideration of scalability, heterogeneity, and availability issues. The Mentor project, introduced in this paper, aims to reconcile a rigorous workflow specification method with a distributed middleware architecture as a step towards enterprise-wide solutions. The project uses the formalism of state and activity charts and a commercial tool, Statemate, for workflow specification. A first prototype of Mentor has been built which allows executing specifications in a distributed manner. A major contribution of this paper is the method for transforming a centralized state chart specification into a form that is amenable to a distributed execution and to incorporate the necessary synchronization between different processing entities. Fault tolerance issues are addressed by coupling Mentor with the Tuxedo TP monitor.
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paper_title: Failure handling and coordinated execution of concurrent workflows

paper_content:

Workflow management systems (WFMSs) coordinate the execution of applications distributed over networks. In WFMSs, data inconsistencies can arise due to: the interaction between steps of concurrent threads within a workflow (intra-workflow coordination); the interaction between steps of concurrent workflows (inter-workflow coordination); and the presence of failures. Since these problems have not received adequate attention, this paper focuses on developing the necessary concepts and infrastructure to handle them. First, to deal with inter- and intra-workflow coordination requirements we have identified a set of high level building blocks. Secondly, to handle failures we propose a novel and pragmatic approach called opportunistic compensation and re-execution that allows a workflow designer to customize workflow recovery from correctness as well as performance perspectives. Thirdly based on these concepts we have designed a workflow specification language that expresses new requirements for workflow executions and implemented a run-time system for managing workflow executions while satisfying the new requirements. These ideas are geared towards improving the modeling and correctness properties offered by WFMSs and making them more robust and flexible.
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paper_title: 1 TRANSACTIONS IN TRANSACTIONAL WORKFLOWS

paper_content:

Workflow management systems (WFMSs) are finding wide applicability in small and large organizational settings. Advanced transaction models (ATMs) focus on maintaining data consistency and have provided solutions to many problems such as correctness, consistency, and reliability in transaction processing and database management environments. While such concepts have yet to be solved in the domain of workflow systems, database researchers have proposed to use, or attempted to use ATMs to model workflows. In this paper we survey the work done in the area of transactional workflow systems. We then argue that workflow requirements in large-scale enterprise-wide applications involving heterogeneous and distributed environments either differ or exceed the modeling and functionality support provided by ATMs. We propose that an ATM is unlikely to provide the primary basis for modeling of workflow applications, and subsequently workflow management. We discuss a framework for error handling and recovery in the METEOR2 WFMS that borrows from relevant work in ATMs, distributed systems, software engineering, and organizational sciences. We have also presented various connotations of transactions in real-world organizational processes today. Finally, we point out the need for looking beyond ATMs and using a multi-disciplinary approach for modeling large-scale workflow applications of the future.
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paper_title: A distributed object oriented framework to offer transactional support for long running business processes

paper_content:

Many business processes are both long running and transactional in nature. They are also mostly multi-user processes. Implementations such as the CORBA OTS (Object Transaction Services) modeled on the lock-based systems used for classic transactions do not fully support the requirements of such processes, and as a result, application developers must develop custom-built infrastructure — on an application-by-application basis — to support users' transactional expectations. This paper presents a novel approach to implementing long-lived transactions within distributed object environments. We propose the use of the unit-of-work (UOW) transaction model and framework, an advanced nested transaction model that enables concurrent access to shared data without locking resources. The UOW approach describes a well-structured distributed object architecture that can easily be integrated with distributed object systems. The framework offers uniform (i.e., application independent) structural transaction support for long running business processes and provides them with the semantics of traditional, short, transactions. Use of the framework enables object developers to focus on business logic, with the framework infrastructure providing functions required to support the desired semantics. We discuss the framework programming model, how it provides transactional behavior to long running business processes and some of the research challenges still ahead of us.
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paper_title: Service-oriented computing

paper_content:

Service-oriented computing (SOC) is the computing paradigm that uses software services (or simply se…
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paper_title: Rule-Based Coordination of Distributed Web Service Transactions

paper_content:

Current approaches to transactional support of distributed processes in service-oriented environments are limited to scenarios where the participant initiating the process maintains a controlling position throughout the lifetime of the process. This constraint impedes support of complex processes where participants may only possess limited local views on the overall process. Furthermore, there is little support of dynamic aspects: failure or exit of participants usually leads to cancelation of the whole process. In this paper, we address these limitations by introducing a framework that strengthens the role of the coordinator and allows for largely autonomous coordination of dynamic processes. We first discuss motivating examples and analyze existing approaches to transactional coordination. Subsequently, we present our framework TracG, which is based on WS-BusinessActivity. It contains at its core a set of rules for deciding on the ongoing confirmation or cancelation status of participants' work and protocol extensions for monitoring the progress of a process. Various types of participant vitality for a process are distinguished, facilitating the controlled exit of nonvital participants as well as continuation of a process in case of tolerable failures. The implementation of the framework is presented and discussed regarding interoperability issues.
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paper_title: Revisiting the Behavior of Fault and Compensation Handlers in WS-BPEL

paper_content:

When automating work, it is often desirable to compensate completed work by undoing the work done by one or more activities. In the context of workflow, where compensation actions are defined on nested 'scopes' that group activities, this requires a model of nested compensation---based transactions. The model must enable the automatic determination of compensation order by considering not only the nesting of scopes but also the control dependencies between them. The current standard for Web services workflows, Business Process Execution Language for Web Services (WS-BPEL), has such compensation capabilities. In this paper, we show that the current mechanism in WS-BPEL shows compensation processing anomalies, such as neglecting control link dependencies between nested non-isolated scopes. We then propose an alternate approach that through elimination of default handlers as well as the complete elimination of termination handlers not only removes those anomalies but also relaxes current WS-BPEL restrictions on control links. The result is a new and deterministic model for handling default compensation for scopes in structures where: (1)both fault handling and compensation handling are present and (2)the relationships between scopes include both structured nesting and graph---based links.
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paper_title: Web Service Composition Transaction Management

paper_content:

The development of new web services by composition of existing services is becoming an extensive approach. This has resulted in transactions that span in multiple web services. These business transactions may be unpredictable and long in duration. Thus they may not be acceptable to lock resources exclusively for such long period. Two-phase commit is also not suitable for transactions with some long sub-transactions. Compensation is a way to ensure transaction reliability. However, rolling back a previously completed transaction is potentially expensive. Thus, tentative holding is another option. This paper presents a transaction management model for web service composition. We apply the approach of tentative hold and compensation for the composite transaction. We also present a multi-dimension negotiation model for the service composition.
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paper_title: A reservation-based coordination protocol for Web services

paper_content:

Traditional transaction semantics are not appropriate for business activities that involve long-running transactions in a loosely-coupled distributed environment, in particular, for Web services that operate between different enterprises over the Internet. In this paper we describe a novel reservation-based extended transaction protocol that can be used to coordinate such business activities. The protocol avoids the use of compensating transactions, which can result in undesirable effects. In our protocol, each task within a business activity is executed as two steps. The first step involves an explicit reservation of resources. The second step involves the confirmation or cancellation of the reservation. Each step is executed as a separate traditional short-running transaction. We show how our protocol can be implemented as a reservation protocol on top of the Web services transaction specification or, alternatively, as a coordination protocol on top of the Web services coordination specification.
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paper_title: Delivering Promises for Web Services Applications

paper_content:

Among the problems facing designers of complex multi-participant Web services-based applications is dealing with the consequences of the lack of suitable isolation mechanisms. This deficiency means that concurrent applications can interfere with each other, resulting in race conditions and lost updates. This paper considers a proposed solution to this problem based on 'promises' and shows that this model can be implemented in practice. We consider implementation issues that need to be handled in promise-based systems and discuss a proof of concept prototype that supports promise-based isolation without requiring changes to existing applications and resources.
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paper_title: Decentralized data dependency analysis for concurrent process execution

paper_content:

This paper presents our results with the investigation of decentralized data dependency analysis among concurrently executing processes in a service-oriented environment. Distributed Process Execution Agents (PEXAs) are responsible for controlling the execution of processes that are composed of web services. PEXAs are also associated with specific distributed sites for the purpose of capturing data changes that occur at those sites in the context of service executions using Delta-Enabled Grid Services. PEXAs then exchange this information with other PEXAs to dynamically discover data dependencies that can be used to enhance recovery activities for concurrent processes that execute with relaxed isolation properties. This paper outlines the functionality of PEXAs, describing the data structures and communication mechanisms that are used to support decentralized construction of distributed process dependency graphs, demonstrating a more dynamic and intelligent approach to identifying how the failure of one process can potentially affect other concurrently executing processes.
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paper_title: Using Rules and Data Dependencies for the Recovery of Concurrent Processes in a Service-Oriented Environment

paper_content:

This paper presents a recovery algorithm for service execution failure in the context of concurrent process execution. The recovery algorithm was specifically designed to support a rule-based approach to user-defined correctness in execution environments that support a relaxed form of isolation for service execution. Data dependencies are analyzed from data changes that are extracted from database transaction log files and generated as a stream of deltas from Delta-Enabled Grid Services. The deltas are merged by time stamp to create a global schedule of data changes that, together with the process execution context, are used to identify processes that are read and write dependent on failed processes. Process interference rules are used to express semantic conditions that determine if a process that is dependent on a failed process should recover or continue execution. The recovery algorithm integrates a service composition model that supports nested processes, compensation, contingency, and rollback procedures with the data dependency analysis process and rule execution procedure to provide a new approach for addressing consistency among concurrent processes that access shared data. We present the recovery algorithm and also discuss our results with simulation and evaluation of the concurrent process recovery algorithm.
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paper_title: Using deltas to analyze data dependencies and semantic correctness in the recovery of concurrent process execution

paper_content:

This research has developed an approach for analyzing data dependencies in a distributed environment, providing a rule-based mechanism to support semantic correctness in the recovery of concurrently executing processes over Grid Services. Delta-Enabled Grid Services are used to capture incremental data changes, known as deltas, from processes that execute over distributed services. Deltas are forwarded to a Process History Capture System (PHCS) that constructs a global process execution history to support the analysis of data dependencies when process failure occurs. An abstract execution model has been developed that is composed of three sub-models: (1) a service composition and recovery model defining the hierarchical composition structure with recovery features for backward recovery and forward execution; (2) a process dependency model defining and analyzing read and write dependencies among concurrently executing processes; and, (3) a rule-based model that uses process interference rules to specify how failure recovery of one process can potentially affect other process execution based on application semantics. A Process Recovery System (PRS) implements the recovery algorithms associated with the abstract execution model. A simulation framework has been developed to demonstrate the functionality of the PHCS and PRS for concurrent process recovery and to conduct performance evaluation on the PHCS and PRS. The results of this research support relaxed isolation and application-dependent semantic correctness for concurrent process execution, with a unique approach to resolving the impact of process failure and recovery on other concurrently executing processes, using data dependencies derived from distributed, autonomous services.
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paper_title: Concurrency control issues in Grid databases

paper_content:

Grid architecture is a fast evolving distributed computing architecture. The working of databases in the Grid architecture is not well understood. In view of changing distributed architecture we strongly feel that concurrency control issues should be revisited and reassessed for this new and evolving architecture. Implementing global lock table and global log records may not be practically possible in the Grid architecture due to the scalability issues. In this paper, we propose a correctness criterion and the Grid concurrency control protocol, which has the capability to deal with heterogeneity, autonomy, distribution and high volume of data in Grids. We then prove the correctness of the protocol followed by performance evaluation of the protocol.
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paper_title: High-Performance Parallel Database Processing and Grid Databases

paper_content:

This book targets the theoretical/conceptual details needed to form a base of understanding and then delivers information on development, implementations, and analytical modeling of parallel databases. It includes key information on new developments with grid databases. Also uses a theoretical and practical balance to support in-depth study of parallel query processing offered by modern DBMS as well as hands on experience of parallel query algorithms development, implementation, and analysis.
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paper_title: Monitoring Data Dependencies in Concurrent Process Execution through Delta-Enabled Grid Services

paper_content:

This paper presents our results with monitoring data dependencies among concurrently executing, distributed processes that execute over grid services. The research has been conducted in the context of the DeltaGrid project, focusing on the development of a semantically robust execution environment for the composition of grid services. Delta-Enabled Grid Services (DEGS) are a foundational aspect of the DeltaGrid environment, extending grid services with the capability of recording incremental data changes, known as deltas. Deltas generated by DEGS are forwarded to a Process History Capture System (PHCS) that organises deltas from distributed sources into a global, time-sequenced schedule of data changes. The design and construction of DEGS is presented, along with the storage and indexing techniques for merging deltas from multiple DEGS to create a global schedule of data changes that can be analysed to determine how the failure and recovery of one process can potentially affect other data-dependent processes. The paper also summarises the performance results for the global history construction and retrieval process.
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paper_title: Process Dependencies and Process Interference Rules for Analyzing the Impact of Failure in a Service Composition Environment

paper_content:

This paper presents a process dependency model for dynamically analyzing data dependencies among concurrently executing processes in an autonomous, distributed service composition environment. Data dependencies are derived from incremental data changes captured at each service execution site. Deltas are then used within a rule-based recovery model to specify how failure recovery of one process can potentially affect another process execution based on application semantics. This research supports relaxed isolation and application-dependent semantic correctness for concurrent process execution, with a unique approach to resolving the impact of process failure recovery on other processes, using data dependencies that are dynamically derived from distributed, autonomous services.
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paper_title: The dynamics of process modeling: new directions for the use of events and rules in service-oriented computing

paper_content:

The introduction of service-oriented computing has created a more dynamic environment for the composition of software applications, where processes are affected by events and data changes and also pose data consistency issues that must be considered in application design and development. This chapter addresses the need to develop a more effective means to model the dynamic aspects of processes in contemporary, distributed applications, especially in the context of concurrently executing processes that access shared data and cannot enforce traditional transaction properties. After an assessment of current tools for process modeling, we outline four approaches for the use of events and rules to support dynamic behavior associated with constraint checking, exception handling, and recovery. The specific techniques include the use of integration rules, assurance points, application exception rules, and invariants. The chapter concludes with a discussion of future research directions for the integrated modeling of events, rules, and processes.
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paper_title: Using Rules and Data Dependencies for the Recovery of Concurrent Processes in a Service-Oriented Environment

paper_content:

This paper presents a recovery algorithm for service execution failure in the context of concurrent process execution. The recovery algorithm was specifically designed to support a rule-based approach to user-defined correctness in execution environments that support a relaxed form of isolation for service execution. Data dependencies are analyzed from data changes that are extracted from database transaction log files and generated as a stream of deltas from Delta-Enabled Grid Services. The deltas are merged by time stamp to create a global schedule of data changes that, together with the process execution context, are used to identify processes that are read and write dependent on failed processes. Process interference rules are used to express semantic conditions that determine if a process that is dependent on a failed process should recover or continue execution. The recovery algorithm integrates a service composition model that supports nested processes, compensation, contingency, and rollback procedures with the data dependency analysis process and rule execution procedure to provide a new approach for addressing consistency among concurrent processes that access shared data. We present the recovery algorithm and also discuss our results with simulation and evaluation of the concurrent process recovery algorithm.
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paper_title: Using deltas to analyze data dependencies and semantic correctness in the recovery of concurrent process execution

paper_content:

This research has developed an approach for analyzing data dependencies in a distributed environment, providing a rule-based mechanism to support semantic correctness in the recovery of concurrently executing processes over Grid Services. Delta-Enabled Grid Services are used to capture incremental data changes, known as deltas, from processes that execute over distributed services. Deltas are forwarded to a Process History Capture System (PHCS) that constructs a global process execution history to support the analysis of data dependencies when process failure occurs. An abstract execution model has been developed that is composed of three sub-models: (1) a service composition and recovery model defining the hierarchical composition structure with recovery features for backward recovery and forward execution; (2) a process dependency model defining and analyzing read and write dependencies among concurrently executing processes; and, (3) a rule-based model that uses process interference rules to specify how failure recovery of one process can potentially affect other process execution based on application semantics. A Process Recovery System (PRS) implements the recovery algorithms associated with the abstract execution model. A simulation framework has been developed to demonstrate the functionality of the PHCS and PRS for concurrent process recovery and to conduct performance evaluation on the PHCS and PRS. The results of this research support relaxed isolation and application-dependent semantic correctness for concurrent process execution, with a unique approach to resolving the impact of process failure and recovery on other concurrently executing processes, using data dependencies derived from distributed, autonomous services.
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paper_title: Supporting data consistency in concurrent process execution with assurance points and invariants

paper_content:

This research has developed the concept of invariant rules for monitoring data in a service-oriented environment that allows concurrent data accessibility with relaxed isolation. The invariant rule approach is an extension of the assurance point concept, where an assurance point is a logical and physical checkpoint that is used to store critical data values and to check pre and post conditions related to service execution. Invariant rules provide a stronger way of monitoring constraints and guaranteeing that a condition holds for a specific duration of execution as defined by starting and ending assurance points, using the change notification capabilities of Delta-Enabled Grid Services. This paper outlines the specification of invariant rules as well as the invariant monitoring system for activating invariants, evaluating invariant rule conditions, and deactivating invariants. The system is supported by an invariant evaluation web service that uses materialized views for more efficient re-evaluation of invariant rule conditions. The research includes a performance analysis of the invariant evaluation Web Service. The strength of the invariant rule technique is that it provides a way to monitor data consistency in an environment where the coordinated locking of data items across multiple service executions is not possible.
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paper_title: Monitoring Data Dependencies in Concurrent Process Execution through Delta-Enabled Grid Services

paper_content:

This paper presents our results with monitoring data dependencies among concurrently executing, distributed processes that execute over grid services. The research has been conducted in the context of the DeltaGrid project, focusing on the development of a semantically robust execution environment for the composition of grid services. Delta-Enabled Grid Services (DEGS) are a foundational aspect of the DeltaGrid environment, extending grid services with the capability of recording incremental data changes, known as deltas. Deltas generated by DEGS are forwarded to a Process History Capture System (PHCS) that organises deltas from distributed sources into a global, time-sequenced schedule of data changes. The design and construction of DEGS is presented, along with the storage and indexing techniques for merging deltas from multiple DEGS to create a global schedule of data changes that can be analysed to determine how the failure and recovery of one process can potentially affect other data-dependent processes. The paper also summarises the performance results for the global history construction and retrieval process.
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paper_title: Transparent Fault Tolerance for Web Services Based Architectures

paper_content:

Service-based architectures enable the development of new classes of Grid and distributed applications. One of the main capabilities provided by such systems is the dynamic and flexible integration of services, according to which services are allowed to be a part of more than one distributed system and simultaneously serve different applications. This increased flexibility in system composition makes it difficult to address classical distributed system issues such as fault-tolerance. While it is relatively easy to make an individual service fault-tolerant, improving fault-tolerance of services collaborating in multiple application scenarios is a challenging task. In this paper, we look at the issue of developing fault-tolerant service-based distributed systems, and propose an infrastructure to implement fault tolerance capabilities transparent to services.
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paper_title: The DeltaGrid Service Composition and Recovery Model

paper_content:

This research has defined an abstract execution model for establishing user-defined correctness and recovery in a service composition environment. The service composition model defines a flexible, hierarchical service composition structure, where a service is composed of atomic and/or composite groups. The model provides multi-level protection against service execution failure by using compensation and contingency at different composition granularity levels, thus maximizing the potential for forward recovery of a process when failure occurs. The recovery procedures also include rollback as a recovery option, where incremental data changes known as deltas are extracted from service executions and externalized by streaming data changes to a Process History Capture System. Deltas can then be used to backward recover an operation through a process known as Delta-Enabled Rollback. This article defines the semantics of the service composition model and the manner in which compensation, contingency, and Delta-Enabled-rollback are used together to recover process execution. The authors also present a case study and describe a simulation and evaluation framework for demonstrating the functionality of the recovery algorithm and for evaluating the performance of the recovery command generation process.
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paper_title: Checkpointing for workflow recovery

paper_content:

Workflow technology targets supporting reliable and scaleable execution, for workflow management systems (WfMS) to support large-scale multi-system applications, involving both humans and legacy systems, in distributed and often heterogeneous environments. In case of failures, workflow processes usually need to resume their executions from one of their saved states, called a checkpoint, achieved by saving the states from time to time persistently. The activity of restoring a checkpoint and resuming the execution from the checkpoint is called rollback. Those techniques have long been used in database systems. A checkpoint is an action consistent checkpoint if it represents a state between complete update operations. A consistent state in the database domain is a state when no update transactions were active. This checkpoint representing a consistent state is a transaction consistent checkpoint. A checkpoint does not need to satisfy any consistency constraints. But recovery after failure must always guarantee that the resultant state is transaction consistent even though any checkpoint used may not be. A checkpoint can be either local or global. A local checkpoint is a checkpoint taken locally, with or without cooperation with any other local checkpointing activities at different sites. A local checkpoint can be a fuzzy or consistent checkpoint. During global reconstruction, a set of local checkpoints, usually taken at different site, will be used to find global consistent state. To facilitate the global reconstruction, a global checkpoint, derived from a set of local checkpoints taken at different site, provides a rollback boundary, thus reducing the recovery time
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paper_title: The Assurance Point Model for Consistency and Recovery in Service Composition

paper_content:

This research has defined an abstract execution model for establishing user-defined correctness and recovery in a service composition environment. The service composition model defines a hierarchical service composition structure, where a service is composed of atomic and/or composite groups. The model provides multi-level protection against service execution failure by using compensation and contingency at different composition granularity levels. The model is enhanced with the concept of assurance points (APS) and integration rules, where APs serve as logical and physical checkpoints for user-defined consistency checking, invoking integration rules that check pre and post conditions at different points in the execution process. The unique aspect of APs is that they provide intermediate rollback points when failures occur, thus allowing a process to be compensated to a specific AP for the purpose of rechecking pre-conditions before retry attempts. APs also support a dynamic backward recovery process, known as cascaded contingency, for hierarchically nested processes in an attempt to recover to a previous AP that can be used to invoke contingent procedures or alternate execution paths for failure of a nested process. As a result, the assurance point approach provides flexibility with respect to the combined use of backward and forward recovery options. Petri Nets have been used to define the semantics of the assurance point approach to service composition and recovery. A comparison to the BPEL fault handler is also provided.
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paper_title: Achieving recovery in service composition with assurance points and integration rules

paper_content:

This paper defines the concept of Assurance Points (APs) together with the use of integration rules to provide a flexible way of checking constraints and responding to execution errors in service composition. An AP is a combined logical and physical checkpoint, providing an execution milestone that stores critical data and interacts with integration rules to alter program flow and to invoke different forms of recovery depending on the execution status. During normal execution, APs invoke rules that check pre-conditions, postconditions, and other application rules. When execution errors occur, APs are also used as rollback points. Integration rules can invoke backward recovery to specific APs using compensation as well as forward recovery through rechecking of preconditions before retry attempts or through execution of contingencies and alternative execution paths. APs together with integration rules provide an increased level of consistency checking as well as backward and forward recovery actions.
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paper_title: Process Dependencies and Process Interference Rules for Analyzing the Impact of Failure in a Service Composition Environment

paper_content:

This paper presents a process dependency model for dynamically analyzing data dependencies among concurrently executing processes in an autonomous, distributed service composition environment. Data dependencies are derived from incremental data changes captured at each service execution site. Deltas are then used within a rule-based recovery model to specify how failure recovery of one process can potentially affect another process execution based on application semantics. This research supports relaxed isolation and application-dependent semantic correctness for concurrent process execution, with a unique approach to resolving the impact of process failure recovery on other processes, using data dependencies that are dynamically derived from distributed, autonomous services.
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paper_title: An Overview of AspectJ

paper_content:

Aspect] is a simple and practical aspect-oriented extension to Java With just a few new constructs, AspectJ provides support for modular implementation of a range of crosscutting concerns. In AspectJ's dynamic join point model, join points are well-defined points in the execution of the program; pointcuts are collections of join points; advice are special method-like constructs that can be attached to pointcuts; and aspects are modular units of crosscutting implementation, comprising pointcuts, advice, and ordinary Java member declarations. AspectJ code is compiled into standard Java bytecode. Simple extensions to existing Java development environments make it possible to browse the crosscutting structure of aspects in the same kind of way as one browses the inheritance structure of classes. Several examples show that AspectJ is powerful, and that programs written using it are easy to understand.
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paper_title: Aspect-Oriented Workflow Languages

paper_content:

Most available aspect-oriented languages today are extensions to programming languages However, aspect-orientation, which is a paradigm for decomposition and modularization, is not only applicable in that context In this paper, we introduce aspect-oriented software development concepts to workflow languages in order to improve the modularity of workflow process specifications with respect to crosscutting concerns and crosscutting changes In fact, crosscutting concerns such as data validation and security cannot be captured in a modular way when using the constructs provided by current workflow languages We will propose a concern-based decomposition of workflow process specifications and present the main concepts of aspect-oriented workflow languages using AO4BPEL, which is an aspect-oriented workflow language for Web Service composition.
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paper_title: AO4BPEL: An Aspect-oriented Extension to BPEL

paper_content:

Process-oriented composition languages such as BPEL allow Web Services to be composed into more sophisticated services using a workflow process. However, such languages exhibit some limitations with respect to modularity and flexibility. They do not provide means for a well-modularized specification of crosscutting concerns such as logging, persistence, auditing, and security. They also do not support the dynamic adaptation of composition at runtime. In this paper, we advocate an aspect-oriented approach to Web Service composition and present the design and implementation of AO4BPEL, an aspect-oriented extension to BPEL. We illustrate through examples how AO4BPEL makes the composition specification more modular and the composition itself more flexible and adaptable.
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paper_title: Web services orchestration and choreography

paper_content:

Combining Web services to create higher level, cross-organizational business processes requires standards to model the interactions. Several standards are working their way through industry channels and into vendor products.
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paper_title: The Assurance Point Model for Consistency and Recovery in Service Composition

paper_content:

This research has defined an abstract execution model for establishing user-defined correctness and recovery in a service composition environment. The service composition model defines a hierarchical service composition structure, where a service is composed of atomic and/or composite groups. The model provides multi-level protection against service execution failure by using compensation and contingency at different composition granularity levels. The model is enhanced with the concept of assurance points (APS) and integration rules, where APs serve as logical and physical checkpoints for user-defined consistency checking, invoking integration rules that check pre and post conditions at different points in the execution process. The unique aspect of APs is that they provide intermediate rollback points when failures occur, thus allowing a process to be compensated to a specific AP for the purpose of rechecking pre-conditions before retry attempts. APs also support a dynamic backward recovery process, known as cascaded contingency, for hierarchically nested processes in an attempt to recover to a previous AP that can be used to invoke contingent procedures or alternate execution paths for failure of a nested process. As a result, the assurance point approach provides flexibility with respect to the combined use of backward and forward recovery options. Petri Nets have been used to define the semantics of the assurance point approach to service composition and recovery. A comparison to the BPEL fault handler is also provided.
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paper_title: Transparent Fault Tolerance for Web Services Based Architectures

paper_content:

Service-based architectures enable the development of new classes of Grid and distributed applications. One of the main capabilities provided by such systems is the dynamic and flexible integration of services, according to which services are allowed to be a part of more than one distributed system and simultaneously serve different applications. This increased flexibility in system composition makes it difficult to address classical distributed system issues such as fault-tolerance. While it is relatively easy to make an individual service fault-tolerant, improving fault-tolerance of services collaborating in multiple application scenarios is a challenging task. In this paper, we look at the issue of developing fault-tolerant service-based distributed systems, and propose an infrastructure to implement fault tolerance capabilities transparent to services.
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paper_title: The Assurance Point Model for Consistency and Recovery in Service Composition

paper_content:

This research has defined an abstract execution model for establishing user-defined correctness and recovery in a service composition environment. The service composition model defines a hierarchical service composition structure, where a service is composed of atomic and/or composite groups. The model provides multi-level protection against service execution failure by using compensation and contingency at different composition granularity levels. The model is enhanced with the concept of assurance points (APS) and integration rules, where APs serve as logical and physical checkpoints for user-defined consistency checking, invoking integration rules that check pre and post conditions at different points in the execution process. The unique aspect of APs is that they provide intermediate rollback points when failures occur, thus allowing a process to be compensated to a specific AP for the purpose of rechecking pre-conditions before retry attempts. APs also support a dynamic backward recovery process, known as cascaded contingency, for hierarchically nested processes in an attempt to recover to a previous AP that can be used to invoke contingent procedures or alternate execution paths for failure of a nested process. As a result, the assurance point approach provides flexibility with respect to the combined use of backward and forward recovery options. Petri Nets have been used to define the semantics of the assurance point approach to service composition and recovery. A comparison to the BPEL fault handler is also provided.
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paper_title: Handling faults in decentralized orchestration of composite web services

paper_content:

Composite web services can be orchestrated in a decentralized manner by breaking down the original service specification into a set of partitions and executing them on a distributed infrastructure. The infrastructure consists of multiple service engines communicating with each other over asynchronous messaging. Decentralized orchestration yields performance benefits by exploiting concurrency and reducing the data on the network. Further, decentralized orchestration may be necessary to orchestrate certain composite web services due to privacy and data flow constraints. However, decentralized orchestration also results in additional complexity due to absence of a centralized global state, and overlapping or different life cycles of the various partitions. This makes handling of faults arising from composite service partitions or from the failure of component web services, a challenging task. In this paper we propose a mechanism for handling faults in decentralized orchestration of composite web services. The mechanism includes a strategy for placement of fault handlers and compensation handlers, and schemes for fault propagation and fault recovery. The mechanism is designed to maintain the semantics of the original specification while ensuring minimal overheads.
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paper_title: Automated discovery, interaction and composition of Semantic Web Services

paper_content:

In this paper we introduce a vision for Semantic Web Services, which combine the growing Web services architecture and the Semantic Web and we will propose DAML-S as a prototypical example of an ontology for describing Semantic Web services.
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paper_title: The Assurance Point Model for Consistency and Recovery in Service Composition

paper_content:

This research has defined an abstract execution model for establishing user-defined correctness and recovery in a service composition environment. The service composition model defines a hierarchical service composition structure, where a service is composed of atomic and/or composite groups. The model provides multi-level protection against service execution failure by using compensation and contingency at different composition granularity levels. The model is enhanced with the concept of assurance points (APS) and integration rules, where APs serve as logical and physical checkpoints for user-defined consistency checking, invoking integration rules that check pre and post conditions at different points in the execution process. The unique aspect of APs is that they provide intermediate rollback points when failures occur, thus allowing a process to be compensated to a specific AP for the purpose of rechecking pre-conditions before retry attempts. APs also support a dynamic backward recovery process, known as cascaded contingency, for hierarchically nested processes in an attempt to recover to a previous AP that can be used to invoke contingent procedures or alternate execution paths for failure of a nested process. As a result, the assurance point approach provides flexibility with respect to the combined use of backward and forward recovery options. Petri Nets have been used to define the semantics of the assurance point approach to service composition and recovery. A comparison to the BPEL fault handler is also provided.
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paper_title: LTSA-WS: a tool for model-based verification of web service compositions and choreography

paper_content:

In this paper we describe a tool for a model-based approach to verifying compositions of web service implementations. The tool supports verification of properties created from design specifications and implementation models to confirm expected results from the viewpoints of both the designer and implementer. Scenarios are modeled in UML, in the form of Message Sequence Charts (MSCs), and then compiled into the Finite State Process (FSP) process algebra to concisely model the required behavior. BPEL4WS implementations are mechanically translated to FSP to allow an equivalence trace verification process to be performed. By providing early design verification and validation, the implementation, testing and deployment of web service compositions can be eased through the understanding of the behavior exhibited by the composition. The approach is implemented as a plug-in for the Eclipse development environment providing cooperating tools for specification, formal modeling, verification and validation of the composition process.
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paper_title: Enhancing BPEL scenarios with Dynamic Relevance-Based Exception Handling

paper_content:

Web services have become the key technology in business processes management. Business processes can be self-contained or be composed from sub-processes; the latter category is typically specified using the Web services business process execution language (WS-BPEL) and executed by a Web services orchestrator (WSO). During the execution however of such a composite service, a number of faults stemming from the distributed nature of the SOA architecture, e.g. network or server failures may occur. WS-BPEL includes provisions for exception handling, which can be exploited for detecting such failures; once detected, a failure can be resolved by invoking alternate Web service implementations that perform the same business task as the failed one. However, the inclusion of such provisions is a tedious assignment for the business process designer, while additional effort would be required to maintain the BPEL scenarios in cases that some alternate WS implementations cease to exist or new ones are introduced. In our research we are developing a framework for automating handling of that kind of exceptions. The proposed solution employs a pre-processor that enhances BPEL scenarios with code that detects failures, discovers alternate WS implementations and invokes them, fully thus resolving the exception. Alternate WS implementation discovery is based on service relevance, which takes into account both functional and qualitative properties of Web services.
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paper_title: Periodic Checkpointing for Strong Mobility of Orchestrated Web Services

paper_content:

Web service composition allows a fast and modular creation of applications by orchestrating several Web services. Such applications are frequently faced to performance and availability problems which may affect the partner Web services or the orchestration process itself. This requires mechanisms for adapting the architecture and the behaviour to this variable context. In this paper, we deal with strong mobility of orchestration processes as a mechanism for adaptation. We provide a solution that relies on checkpoint/rollback mechanisms. It is also based on source code transformation of the orchestration process. We apply our approach on WS-BPEL based orchestration processes. Hence, we establish a set of rules which transform WS-BEPL processes to equivalent mobile ones. When an adaptation is to be performed,the execution of some or all instances of a mobile process will be interrupted, and then they will be migrated to another node. After migration, the interrupted instances will resume starting from the last checkpoint. Experimentation results show the the efficiency of our approach and the low overhead it introduces.
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paper_title: Revisiting the Behavior of Fault and Compensation Handlers in WS-BPEL

paper_content:

When automating work, it is often desirable to compensate completed work by undoing the work done by one or more activities. In the context of workflow, where compensation actions are defined on nested 'scopes' that group activities, this requires a model of nested compensation---based transactions. The model must enable the automatic determination of compensation order by considering not only the nesting of scopes but also the control dependencies between them. The current standard for Web services workflows, Business Process Execution Language for Web Services (WS-BPEL), has such compensation capabilities. In this paper, we show that the current mechanism in WS-BPEL shows compensation processing anomalies, such as neglecting control link dependencies between nested non-isolated scopes. We then propose an alternate approach that through elimination of default handlers as well as the complete elimination of termination handlers not only removes those anomalies but also relaxes current WS-BPEL restrictions on control links. The result is a new and deterministic model for handling default compensation for scopes in structures where: (1)both fault handling and compensation handling are present and (2)the relationships between scopes include both structured nesting and graph---based links.
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paper_title: The Consistency of Web Conversations

paper_content:

We describe BPELCheck, a tool for statically analyzing interactions of composite Web services implemented in BPEL. Our algorithm is compositional, and checks each process interacting with an abstraction of its peers, without constructing the product state space. Interactions between pairs of peer processes are modeled using conversation automata which encode the set of valid message exchange sequences between the two processes. A process is consistent if each possible conversation leaves its peer automata in a state labeled as consistent and the overall execution satisfies a user-specified predicate on the automata states. We have implemented BPELCheck in the Enterprise Service Pack of the NetBeans development environment. Our tool handles the major syntactic constructs of BPEL, including sequential and parallel composition, exception handling, flows, and Boolean state variables. We have used BPELCheck to check conversational consistency for a set of BPEL processes, including an industrial example.
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paper_title: Self-healing BPEL processes with Dynamo and the JBoss rule engine

paper_content:

Many emerging domains such as ambient intelligence, context-aware applications, and pervasive computing are embracing the assumption that their software applications will be deployed in an open-world. By adopting the Service Oriented Architecture paradigm, and in particular its Web service based implementation, they are capable of leveraging components that are remote and not under their jurisdication, i.e. services. However, the distributed nature of these systems, the presence of many stakeholders, and the fact that no one has a complete knowledge of the system preclude classic static verification techniques. The capability to "self-heal" has become paramount. In this paper we present our solution to self-healing BPEL compositions called Dynamo. It is an assertion-based solution, that provides special purpose languages (WSCoL and WSReL) for defining monitoring and recovery activities. These are executed using Dynamo, which consists of an AOP-extended version of the ActiveBPEL orchestration engine, and which leverages the JBoss Rule Engine to ensure self-healing capabilities. The approach is exemplified on a complex case study.
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paper_title: The Pi-Calculus: A Theory of Mobile Processes

paper_content:

From the Publisher: ::: Mobile systems, whose components communicate and change their structure, now pervade the informational world and the wider world of which it is a part. The science of mobile systems is as yet immature, however. This book presents the pi-calculus, a theory of mobile systems. The pi-calculus provides a conceptual framework for understanding mobility, and mathematical tools for expressing systems and reasoning about their behaviors. ::: The book serves both as a reference for the theory and as an extended demonstration of how to use pi-calculus to describe systems and analyze their properties. It covers the basic theory of pi-calculus, typed pi-calculi, higher-order processes, the relationship between pi-calculus and lambda-calculus, and applications of pi-calculus to object-oriented design and programming. ::: The book is written at the graduate level, assuming no prior acquaintance with the subject, and is intended for computer scientists interested in mobile systems.
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paper_title: A bidirectional heuristic search technique for web service composition

paper_content:

Automatic web services composition has recently received considerable attention from researchers in different fields. In this paper we propose a model based on web service dependency graph and a bidirectional heuristic search algorithm to find composite web services. The proposed algorithm is based on a new domain independent heuristic. Experiments on different types of dependency graphs of varying sizes and number of web services show promising results for the service composition model when compared to state-of-the-art search algorithms. The proposed dependency graph based composition model is, however, not limited to traditional web services but it can be extended to more general frameworks of collective systems where a global intelligent behavior emerges by a plurality of agents which interact composing different actions, services, or resources.
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paper_title: WSAT: A Tool for Formal Analysis of Web Services

paper_content:

This paper presents Web Service Analysis Tool (WSAT), a tool for analyzing and verifying composite web service designs, with the state of the art model checking techniques. Web services are loosely coupled distributed systems communicating via XML messages. Communication among web services is asynchronous, and it is supported by messaging platforms such as JMS which provide FIFO queues to store incoming messages. Data transmission among web services is standardized via XML, and the specification of web service itself (invocation interface and behavior signature) relies on a stack of XML based standards (e.g. WSDL, BPEL4WS, WSCI and etc.). The characteristics of web services, however, raise several challenges in the application of model checking: (1) Numerous competing web service standards, most of which lack formal semantics, complicate the formal specification of web service composition. (2) Asynchronous messaging makes most interesting verification problems undecidable, even when XML message contents are abstracted away [3]. (3) XML data and expressive XPath based manipulation are not supported by current model checkers.
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paper_title: A Petri Net-based Model for Web Service Composition

paper_content:

The Internet is going through several major changes. It has become a vehicle of Web services rather than just a repository of information. Many organizations are putting their core business competencies on the Internet as a collection of Web services. An important challenge is to integrate them to create new value-added Web services in ways that could never be foreseen forming what is known as Business-to-Business (B2B) services. Therefore, there is a need for modeling techniques and tools for reliable Web service composition. In this paper, we propose a Petri net-based algebra, used to model control flows, as a necessary constituent of reliable Web service composition process. This algebra is expressive enough to capture the semantics of complex Web service combinations.
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paper_title: Transparent Fault Tolerance for Web Services Based Architectures

paper_content:

Service-based architectures enable the development of new classes of Grid and distributed applications. One of the main capabilities provided by such systems is the dynamic and flexible integration of services, according to which services are allowed to be a part of more than one distributed system and simultaneously serve different applications. This increased flexibility in system composition makes it difficult to address classical distributed system issues such as fault-tolerance. While it is relatively easy to make an individual service fault-tolerant, improving fault-tolerance of services collaborating in multiple application scenarios is a challenging task. In this paper, we look at the issue of developing fault-tolerant service-based distributed systems, and propose an infrastructure to implement fault tolerance capabilities transparent to services.
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paper_title: Checkpointing for workflow recovery

paper_content:

Workflow technology targets supporting reliable and scaleable execution, for workflow management systems (WfMS) to support large-scale multi-system applications, involving both humans and legacy systems, in distributed and often heterogeneous environments. In case of failures, workflow processes usually need to resume their executions from one of their saved states, called a checkpoint, achieved by saving the states from time to time persistently. The activity of restoring a checkpoint and resuming the execution from the checkpoint is called rollback. Those techniques have long been used in database systems. A checkpoint is an action consistent checkpoint if it represents a state between complete update operations. A consistent state in the database domain is a state when no update transactions were active. This checkpoint representing a consistent state is a transaction consistent checkpoint. A checkpoint does not need to satisfy any consistency constraints. But recovery after failure must always guarantee that the resultant state is transaction consistent even though any checkpoint used may not be. A checkpoint can be either local or global. A local checkpoint is a checkpoint taken locally, with or without cooperation with any other local checkpointing activities at different sites. A local checkpoint can be a fuzzy or consistent checkpoint. During global reconstruction, a set of local checkpoints, usually taken at different site, will be used to find global consistent state. To facilitate the global reconstruction, a global checkpoint, derived from a set of local checkpoints taken at different site, provides a rollback boundary, thus reducing the recovery time
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paper_title: Formal modeling of BPEL workflows including fault and compensation handling

paper_content:

Electronically executed business processes are frequently implemented using the Business Process Execution Language (BPEL). These workflows may be in control of crucial business processes of an organization, in the same time existing model checking approaches are still immature i.e. they either seem to loose to much information during the generation of the analysis model, or the state space explosion prevents from model checking. We present a formal modeling technique for BPEL workflows including fault and compensation handling providing exact semantics with a state space size that allows for model checking. Additionally, error propagation among variables is supported so the effect of a faulty activity on the entire process can be examined.
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paper_title: A Fault Taxonomy for Web Service Composition

paper_content:

Web services are becoming progressively popular in the building of both inter- and intra-enterprise business processes. These processes are composed from existing Web services based on defined requirements. In collecting together the services for such a composition, developers can employ languages and standards for the Web that facilitate the automation of Web service discovery, execution, composition and interoperation. However, there is no guarantee that a composition of even very good services will always work. Mechanisms are being developed to monitor a composition and to detect and recover from faults automatically. A key factor in such self-healing is to know what faults to look for. If the nature of a fault is known, the system can suggest a suitable recovery mechanism sooner. This paper proposes a novel taxonomy that captures the possible failures that can arise in Web service composition, and classifies the faults that might cause them. The taxonomy covers physical, development and interaction faults that can cause a variety of observable failures in a system's normal operation. An important use of the taxonomy is identifying the faults that can be excluded when a failure occurs. Examples of using the taxonomy are presented.
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paper_title: Semantic web services discovery based on structural ontology matching

paper_content:

In this paper, we present an approach to semantic-based web service discovery and a prototypical tool based on syntactic and structural schema matching. It is based on matching an input ontology, describing a service request, to web services descriptions at the 'syntactic level' through Web Services Description Language (WSDL) or, at the semantic level, through service ontologies described with languages such as Ontology Web Language for Services (OWL-S), Web Services Modelling Ontology (WSMO), Semantic Web Services Framework (SWSF) and Web Services Description Language Semantics (WSDL-S). The different input schemas, WSDL descriptions, Ontology Web Language (OWL) ontologies, OWL-S, WSMO, SWSF and WSDL-S components are represented in a uniform way by means of directed rooted graphs, where nodes represent schema elements, connected by directed links of different types, e.g., for containment and referential relationships. On this uniform internal representation, a number of matching algorithms operate, including structural-based algorithms (Children Matcher, Leaves Matcher, Graph and SubGraph Isomorphism) and syntactical ones (Edit Distance (Levenshtein Distance or LD) and Synonym Matcher (through the WordNet synonyms thesaurus)).
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paper_title: A framework to coordinate web services in composition scenarios

paper_content:

This paper looks into the coordination of web services following their acceptance to participate in a composition scenario. We identify two types of behaviours associated with component web services: operational and control behaviours. These behaviours are used to specify composite web services that are built upon component web services. In term of orchestration a composite web service could be either centralised or peer-to-peer. To support component/composite web services coordination per type of orchestration schema, various types of messages are exchanged between these web services. Experiments showing the use of these messages are reported in this paper as well.
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Title: A Survey of Transactional Issues for Web Service Composition and Recovery

Section 1: Introduction
Description 1: Introduce the background of web services, service-oriented architecture, and the need for handling transactional issues and recovery in web service composition.

Section 2: A Historical Perspective of Advanced Transaction and Workflow Models
Description 2: Present relevant background on advanced transaction models and transactional workflows that influence current techniques for web service composition and recovery.

Section 3: Advanced Transaction Models
Description 3: Discuss various advanced transaction models such as Sagas, Nested Transaction Model, Multi-level Transaction Model, and Flexible Transaction Model.

Section 4: Transactional Workflow
Description 4: Explore the concept of transactional workflows, their properties, and techniques for achieving failure recovery in workflow environments.

Section 5: Standards for Web Service Transactions and Composition
Description 5: Summarize the standards associated with transactional issues for web services and the Business Process Execution Language for service composition and recovery.

Section 6: Web Service Specifications
Description 6: Outline relevant web service specifications, including WS-Coordination, WS-Transaction, and WS-Business Activity, and their roles in transactional support.

Section 7: Web Services Business Process Execution Language
Description 7: Describe the main concepts of WS-BPEL 2.0, including its activities, handlers, and recovery mechanisms.

Section 8: Relaxed Semantics and Locking Techniques
Description 8: Discuss relaxed locking techniques such as Tentative Hold, reservation-based approach, and Promises approach for addressing data consistency.

Section 9: Data Dependency Analysis
Description 9: Present techniques for data dependency analysis among concurrent processes and their impact on recovery procedures.

Section 10: The Assurance Point System
Description 10: Describe the Assurance Point System, including its hierarchical structure, usage of logical and physical checkpoints, and user-defined correctness conditions.

Section 11: Functional Modularization With Aspect-Oriented Techniques
Description 11: Explore the application of aspect-oriented techniques in workflow languages to provide modularization and address cross-cutting concerns.

Section 12: Failure Recovery Strategies for Web Services
Description 12: Summarize research on different failure recovery strategies for web services, such as re-do, un-do, and alternative strategies, and discuss self-healing and checkpointing mechanisms.

Section 13: Conclusion and Future Work
Description 13: Conclude the paper by summarizing the research discussed and outlining future research directions for transactional handling and recovery in web service composition.