Wing Lok Yeung

A framework for effective commercial web application development

The World Wide Web (WWW) or the Web has been recognized as a powerful new information exchange channel in recent years. Today, an ever‐increasing number of businesses have set up Web sites to publicize their products and services. However, careful planning and preparation is needed to achieve the intended purpose of this new information exchange channel. This paper proposes a comprehensive framework for effective commercial Web application development based on prior research in hypermedia and human‐computer interfaces. The framework regards Web application development as a special type of software development project. At the onset of the project, its social acceptability is investigated. Next, economic, technical, operational, and organizational viability are examined. For Web page design, both the functionality and usability of Web pages are thoroughly considered. The use of the framework should result in more effective commercial Web application development.

Mapping WS-CDL and BPEL into CSP for Behavioural Specification and Verification of Web Services

The Web service Business Process Execution Language (WS-BPEL) and the Web service Choreography Description Language (WS-CDL) are two important standards for modelling and implementing workflows and business processes based on Web services. From the WS-CDL description of a Web services based business process, we may extract a behavioural specification against which the combined behaviour of the participating Web services should be verified. We show how to express this behavioural specification as well as the behaviour of individual WS-BPEL-based Web services in the formalism of communicating sequential processes (CSP), which supports a formal approach to verifying the behaviour of collaborating Web services

Improvements towards formalizing UML state diagrams in CSP

The Unified Modelling Language (UML) includes a variant of state charts, called state diagrams (SD), for modelling systems with complex interactive behaviour. The official definition of UML specifies the abstract syntax of state diagrams without any formal semantics and hence is unable to perform formal system behaviour analysis. Various attempts have been made to provide such a formal basis for UML state diagrams. Among different attempts, the work reported in [Muan Yong Ng et al. (2003)] is formalizing SD in terms of communicating sequential processes (CSP). In this paper, we present some improvements upon the formalization. The improvements help clarify the semantics of UML SD and make the formalization more complete. Furthermore, we illustrate the use of CSP in reasoning about the equivalence of state diagrams and discuss the benefits of the formalization.

Denotational semantics for JSD

This paper discusses the use of denotational semantics in formalizing the notations of structured methods. Using the Jackson System Development (JSD) method as an example, the techniques of denotational semantics are applied to the JSD notations to give them a formal semantics based on lambda calculus and communicating sequential processes (CSP). A JSD design can then be readily translated into CSP based on the semantic definition.

CSP-Based Verification for Web Service Orchestration and Choreography

Service-oriented computing aspires to an unprecedented level of platform-independence and inter-operability of software components for intra- and inter-organizational business processes through standard protocols and languages for workflows and process-oriented applications. The Web Service Business Process Execution Language (WS-BPEL) and the Web Service Choreography Description Language (WS-CDL) are two major languages for modeling and implementing Web services-based business processes. A Web service can be modeled in WS-BPEL by an abstract process describing its external behavior in terms of message exchanges with other participants (Web services). The abstract process can then be refined with more details to become an executable process. On the other hand, WS-CDL serves as a behavioral modeling language for the collaboration between multiple participants (Web services) within the same business process from a global point of view. In this paper, we outline how Communicating Sequential Processes (CSP) can be used as a formal basis for verifying the behavioral consistency among abstract and executable processes together with choreographic descriptions.

Behavioral modeling and verification of multi-agent systems for manufacturing control

Abstract Simulation is the primary approach to the performance analysis of multi-agent manufacturing systems. In a typical simulation experiment, varying the agent negotiation protocol’s timing parameters can yield incomparable results in performance terms due to behavioral problems such as deadlocks and livelocks. Formal verification can help resolve such problems and therefore plays an important role in the design of agent negotiation protocols. We describe an efficient and scalable approach to formal verification based on an industrial-strength model checking tool and illustrate it with an example.

Design and Verification of Distributed Recovery Blocks with CSP

A case study on the application of Communicating Sequential Processes (CSP) to the design and verification of fault-tolerant real-time systems is presented. The distributed recovery block (DRB) scheme is a design technique for the uniform treatment of hardware and software faults in real-time systems. Through a simple fault-tolerant real-time system design using the DRB scheme, the case study illustrates a paradigm for specifying fault-tolerant software and demonstrates how the different behavioural aspects of a fault-tolerant real-time system design can be separately and systematically specified, formulated, and verified using an integrated set of formal techniques based on CSP.

Embedded program testing in untestable mobile environment: an experience of trustworthiness approach

Comparing actual output with the expected output of some controlled input is a fundamental principle of program correctness testing. However, in some situations, the input is uncontrollable or even undetectable during testing and, hence, it is impossible to decide the expected output or the test oracle. We encountered this problem when we developed programs to extract network data from various mobile stations in the mobile location estimation system project. We propose testing the trustworthiness of the programs instead. Since the input is uncontrollable and undetectable, program output is analyzed and challenged against with the intrinsic properties, environment, the program output itself and their application results, to find evidence that the output is suitable to be used for the planned purposes. Furthermore, in the case of mobile software development, it is common that different programs of the same specification have to be developed for mobile stations of different models. These different implementations provide another source of reference for trustworthiness tests. Our experience of applying trustworthiness test in extracting network data from mobile stations is reported in this paper.

Verifying Choreographic Descriptions of Web Services Based on CSP

The emerging service-oriented architectures based on Web services is fostering a new generation of intra- and inter-organizational cross-platform Web-based business applications. With the new architectures comes a new set of standards (e.g. XML, SOAP, WSDL, UDDI) for enabling self-describing interoperable Web services, as well as for modeling and implementing workflow or process-oriented Web applications. The latter kind of standards include the Web Service Business Process Execution language (BPEL) and the Web Service Choreography Description Language (WS-CDL). While BPEL supports the modeling and implementation of a particular (composite) Web service, WS-CDL can be seen as a behavioral modeling language for the collaboration between multiple parties (Web services) within the same business process. In this paper, we outline how communicating sequential processes (CSP) can be used as a formal basis for checking the behavioral consistency among the participants of a business process with respect to a choreography. The use of a model checking tool for automating the consistency checking is also discussed

A Formal Basis for Cross-Checking ebXML BPSS Choreography and Web Service Orchestration

ebXML is a global business-to-business (B2B) electronic commerce standard which addresses not only the formats and vocabularies of electronic business documents exchanged between business partners, but also the choreography of business transactions during a collaborative process. On the other hand, the service-oriented architectures (SOA) together with Web services promise a new era for B2B collaboration with dynamically created business partnerships transacting based on published choreographies, for which the ebXML BPSS (business process specification scheme) is a major specification language. To implement such a collaboration process, business partners can package their enterprise applications as Web services and orchestrate them in WS-BPEL according to the published choreography for the process. This paper contributes to the successful implementation of collaborative processes based on Web services by introducing a formal basis for verifying the consistency between ebXML BPSS choreography and WS-BPEL Web service orchestration. We illustrate the approach with a contract negotiation process.