Service orientation fosters a high-level model for distributed applications development, which is based on the discovery, composition and reuse of existing software services. However, the heterogeneity among current service-oriented technologies renders the important task of service discovery tedious and ineffective. This dissertation proposes a new approach to address this challenge. Specifically, it contributes a framework supporting the unified discovery of heterogeneous services, with a focus on web, peer-to-peer, and grid services. The framework comprises a service query language and its enacting service discovery engine. Overall, the proposed solution is characterized by generality and flexibility, which are ensured by appropriate abstractions, extension points, and their sup- porting mechanisms. The viability, performance, and effectiveness of the proposed framework are demonstrated by experimental measurements.
Most of the currently existing languages for service discovery fail to address the heterogeneity in service descriptions and service discovery mechanisms. In @cite_13 @cite_9 , the authors propose the use of XQuery to express queries over service descriptions that are constructed according to specific schemas. Similarly, in @cite_17 @cite_24 , service queries can only be evaluated against WSDL documents. In an effort to address the need for multi-dimensional query formulation, the approach proposed in @cite_12 defines certain extensions to the UDDI specification, still queries are only compliant with registries of that type. Also, numerous approaches that have adopted existing semantic service description languages to express service queries, as for example in @cite_22 , are naturally confined to limited sets of available services.
@cite_22 @cite_9 @cite_24 @cite_13 @cite_12 @cite_17
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The web-services stack of standards is designed to support the reuse and interoperation of software components on the web. A critical step in the process of developing applications based on web services is service discovery, i.e. the identification of existing web services that can potentially be used in the context of a new web application. Discovery through catalog-style browsing (such as supported currently by web-service registries) is clearly insufficient. To support programmatic service discovery, we have developed a suite of methods that assess the similarity between two WSDL (Web Service Description Language) specifications based on the structure of their data types and operations and the semantics of their natural language descriptions and identifiers. Given only a textual description of the desired service, a semantic information-retrieval method can be used to identify and order the most relevant WSDL specifications based on the similarity of the element descriptions of the available specifications with the query. If a (potentially partial) specification of the desired service behavior is also available, this set of likely candidates can be further refined by a semantic structure-matching step, assessing the structural similarity of the desired vs the retrieved services and the semantic similarity of their identifiers. In this paper, we describe and experimentally evaluate our suite of service-similarity assessment methods. Web services have acquired enormous popularity among software developers. This popularity has motivated developers to publish a large number of Web service descriptions in UDDI registries. Although these registries provide search facilities, they are still rather difficult to use and often require service consumers to spend too much time manually browsing and selecting service descriptions. This paper presents a novel search method for Web services called WSQBE that aims at both easing query specification and assisting discoverers by returning a short and accurate list of candidate services. In contrast with previous approaches, WSQBE discovery process is based on an automatic search space reduction mechanism that makes this approach more efficient. Empirical evaluations of WSQBE search space reduction mechanism, retrieval performance, processing time and memory usage, using a registry with 391 service descriptions, are presented. This paper presents an innovative approach for the publication and discovery of Web services. The proposal is based on two previous works: DIRE (DIstributed REgistry), for the user-centered distributed replication of service-related information, and URBE (UDDI Registry By Example), for the semantic-aware match making between requests and available services. The integrated view also exploits USQL (Unified Service Query Language) to provide users with a higher level and homogeneous means to interact with the different registries. The proposal improves background technology in different ways: we integrate USQL as high-level language to state service requests, widen user notifications based on URBE semantic matching, and apply URBE match making to all the facets with which services can be described in DIRE. All these new concepts are demonstrated on a simple scenario. In the current Web Service Description Language (WSDL), only the interface information of a web service is provided without any indication on its behavior logic. Naturally, it is difficult for the service user and developer to achieve a shared understanding of the service behavior through such a description. A particular challenge is how to make explicit the various behavior assumptions and restrictions of a service (for the user), and make sure that the service implementation conforms to them (for the developer). In order to improve the behavior conformance of services, in this paper we propose a constraint-based model-driven testing approach for web services. In our approach, constraints are introduced in an extended WSDL, called CxWSDL, to formally and explicitly express the implicit restrictions and assumptions on the behavior of web services, and then the predefined constraints are used to derive test cases in a model-driven manner to test the service implementation’s conformance to these behavior constraints from the user’s perspective. We have conducted an empirical study with three real-life web services as subject programs, and the experimental results have shown that our approach can effectively validate the service’s conformance to the behavior constraints.