Zhi Fang

Contracting of Web Services with Constraint Handling Rules

In e-service environment, service contract is important for assurance of business interoperability and quality of services. Combining service contract and process model will facilitate analyzing service process and monitoring service execution. This paper proposes a service modeling approach consists of service contract and process model. Service contracts are used as service advertisement and service request in this approach. The operational semantics of service contract and process model are translated into Constraint Handling Rules(CHR) program by a compiler. Based on this approach, a concept named service contracting is defined as a phase between service discovery and execution, which checks the consistency of service advertisement and process model as well as the the applicability of services w.r.t. the consumers capabilities. Further, constraint solver centered implementation is designed, the modeling and contracting of web services under this architecture is illustrated.

Contracting of E-business Services in a Constraint-Based Process Modeling Framework

Analyzing and contracting of E-Business service processes is a crucial step between discovery and execution of Semantic Web Services. This paper proposes a service modelling framework consists of constraint-based service contract, agent style communication messages and service process specification. Service contract is used as shared knowledge between participants and instrument for advertising and requesting of services. The Constraint Process S pecification proposed is capable of describing complex data and control-flow restrictions as well as data content restrictions. A state transition based operational semantic for this framework is given. A virtual machine is built for analyzing and contracting of services. We illustrate the expressiveness of this framework within an online shopping scenario.

Handling SLA Violations via Constraint Imperative Programming

The handling of violations of Service Level Agreement (SLA) is important for trustful service, particularly for web services in business field. In this paper, a SLA specification combines syntactic constructs from WS-Agreement and WSLA is proposed. Violations of SLA are prevented, detected and compensated by ECA (Event-Condition-Action) rules and constraint imperative programming (CIP) techniques. ECA constructor, inspired by the concept of constraint constructor used for handling user-defined constraints in CIP languages, is introduced for building and refactoring of ECA rules.

Verification for commitment-based web service protocols

We propose a model for a class of web services which are powered by relational databases and annotated by social commitment. Our model can be viewed as an extension of WSDL specification where schemas of service operations specify not only input-output signatures but also data constraints, control-flow constraints, state/output/effect rules. The data-aware temporal properties about interactions between services and users are specified in Linear Temporal First-Order Logic with Social Commitment LTL-FO

Modeling and verification for data-centric web services

We propose a model for a class of Web services which are powered by relational databases and respond to users by querying the underlying database as well as the state information of interaction. Our model can be viewed as an extension of WSDL specification where schemas of service operations specify not only input-output signatures but also data constraints, control-flow constraints, and state/output/action rules. The control-flow and more complex data-aware temporal properties about interactions between services and users are specified in Linear Temporal Logic (LTL) and its extension Linear Temporal First-Order Logic (LTL-FO). We have proved it is feasible to existing tools (e.g. SPIN, WAVE) to verify such properties.

Failure handling of E-Business Services in an extensible constraint service model

Failure handling of business transactions is essential in E-Business Services. This paper extends the service process specification proposed in a contract-centered constraint-based service modelling framework with failure handling capabilities. Besides failure in process model, generalized failure such as QoS violation can be modelled in policies. Executable semantics for failure handling in E-Business services as well as policies are discussed via a state transition system. A virtual machine is built for contracting and executing of services under this framework.

A concurrent constraint and pi-calculus-based language for service contracting

In e-service environment, service agreement is essential for assurance of business interoperability and quality of services. Combining service agreement and process model will facilitate analysing service process and monitoring service execution. This paper proposes a concurrent constraint and pi-calculus-based service modelling approach consists of service agreement and process model. Based on this service model, a service contracting mechanism, which checks the consistency between service agreement and process model as well as the applicability of services with respect to the requesters capabilities, is designed.

A Virtual Organization Model Based on Semantic Web Services and Its Application in Supply Chain for Agricultural Product

Cross-Organizational interoperability and coordination are core issues to Virtual Organization (VO) researches. We propose a model of VOs in which VO related concepts are modeled in an extension of the OWL-S service ontology and SWOCRL (Semantic Web Object Constraint Rule Language) rules. Within this framework, VO abilities can be seen as services provided; coordination between VOs can be seen as service invocation. SWOCRL rules are used as mediators between service descriptions and requests. A prototype system of our framework is proposed combining Constraint Handling Rules (CHR) and Prolog.

Bounded Model Checking for Web Service Discovery and Composition

With the acceptance of service-oriented architecture (SOA) in many application domains and the rapidly growing number of available services, it is now a challenge to effectively discover and compose services to meet user needs. In this paper, we present a novel technique for automatic service discovery and composition based on bounded model checking. Specifically, given (1) a client specification of the objective service, described by a linear temporal logic formula, and (2) a set of available services, our technique discoveries these services which behavior satisfies the client specification or synthesizes a composite service that uses only the available services to realize the client specification.