Automated Testing of Web Services Based on Algebraic Specifications

The testing of web services must be done in a completely automated manner when it takes place on-the-fly due to third-party services are dynamically composed to. We present an approach that uses algebraic specification to make this possible. Test data is generated from a formal specification and then used to construct and submit service requests. Test results are then extracted and checked against the specification. All these are done automatically, as required. We present ASSAT (Algebraic Specification-Based Service Automated Testing), a prototype tool that performs these tasks and demonstrate its utility by applying it to Amazon Web Services, a real-life industrial example

Algebraic specification of web services

This paper presents an algebraic specification language for the formal specification of the semantics of web services. A set of rules for transforming WSDL into algebraic structures is proposed. Its practical usability is also demonstrated by an example

Monic Testing of Web Services Based on Algebraic Specifications

Web services are designed to be discovered and composed dynamically, which implies that testing must also be done dynamically. This involves both the generation of test cases and the checking of test results. This paper presents algorithms for both of these using the technique of algebraic specification. It focuses in particular on the problem that web services, when they are third-party, have poor controllability and observability, and introduces a solution known as monic floating checkable test cases. A prototype tool has implemented the proposed testing technique and it is applied to a case study with a real industry application GoGrid, demonstrating that the technique is both applicable and feasible

Evaluating the Ontological Semantic Description of Web Services Generated from Algebraic Specifications

The semantics of web services can be described using ontology or formally specified in mathematical notations. The former is comprehensible and searchable, while the latter is testable and verifiable. To take advantage of both, we proposed, in our previous work, a transformation that takes an algebraic specification of a web service to generate a domain ontology and a semantic description of the service on that ontology. This paper investigates the quality of these two outputs by proposing a general framework of ontology evaluation that assesses them on 4 aspects of quality, which are decomposed into 8 factors and then measured by a set of 37 metrics. It reports a case study on 3 real-life examples of web services. The results show that the ontologies and semantic descriptions generated from formal specifications are of satisfactory quality

Web Services: A Process Algebra Approach

It is now well-admitted that formal methods are helpful for many issues raised in the Web service area. In this paper we present a framework for the design and verification of WSs using process algebras and their tools. We define a two-way mapping between abstract specifications written using these calculi and executable Web services written in BPEL4WS. Several choices are available: design and correct errors in BPEL4WS, using process algebra verification tools, or design and correct in process algebra and automatically obtaining the corresponding BPEL4WS code. The approaches can be combined. Process algebra are not useful only for temporal logic verification: we remark the use of simulation/bisimulation both for verification and for the hierarchical refinement design method. It is worth noting that our approach allows the use of any process algebra depending on the needs of the user at different levels (expressiveness, existence of reasoning tools, user expertise)

Issues about the Adoption of Formal Methods for Dependable Composition of Web Services

Web Services provide interoperable mechanisms for describing, locating and invoking services over the Internet; composition further enables to build complex services out of simpler ones for complex B2B applications. While current studies on these topics are mostly focused - from the technical viewpoint - on standards and protocols, this paper investigates the adoption of formal methods, especially for composition. We logically classify and analyze three different (but interconnected) kinds of important issues towards this goal, namely foundations, verification and extensions. The aim of this work is to individuate the proper questions on the adoption of formal methods for dependable composition of Web Services, not necessarily to find the optimal answers. Nevertheless, we still try to propose some tentative answers based on our proposal for a composition calculus, which we hope can animate a proper discussion

A monitoring approach for runtime service discovery

Effective runtime service discovery requires identification of services based on different service characteristics such as structural, behavioural, quality, and contextual characteristics. However, current service registries guarantee services described in terms of structural and sometimes quality characteristics and, therefore, it is not always possible to assume that services in them will have all the characteristics required for effective service discovery. In this paper, we describe a monitor-based runtime service discovery framework called MoRSeD. The framework supports service discovery in both push and pull modes of query execution. The push mode of query execution is performed in parallel to the execution of a service-based system, in a proactive way. Both types of queries are specified in a query language called SerDiQueL that allows the representation of structural, behavioral, quality, and contextual conditions of services to be identified. The framework uses a monitor component to verify if behavioral and contextual conditions in the queries can be satisfied by services, based on translations of these conditions into properties represented in event calculus, and verification of the satisfiability of these properties against services. The monitor is also used to support identification that services participating in a service-based system are unavailable, and identification of changes in the behavioral and contextual characteristics of the services. A prototype implementation of the framework has been developed. The framework has been evaluated in terms of comparison of its performance when using and when not using the monitor component