Web Services Composition Methods and Techniques: A Review <s> III. A: Web Service Composition <s> The development of Web services provides a convenient way to achieve various services on web. Web services composition is the key techniques in its application. Composition of Web service is always in a complex and distributed environment so there are many potential problems such as deadlock. To avoid those problems, we first model Web services as finite state machine and discuss the properties of Web services. Then constraints in composition are discussed exactly. We deliver the process of composition into three parts according to the merging process: constraints before composition, constraints in composition and constraints after composition. According to different steps, constraints of Web services composition are analyzed. Based on the discussion, a modified model is given with the constraint considerate. Model with constraints makes composition of Web services safe and effective in complex environment. <s> BIB001 </s> Web Services Composition Methods and Techniques: A Review <s> III. A: Web Service Composition <s> This paper proposes a semantic Web service discovery framework for finding semantic Web services by making use of natural language processing techniques. The framework allows searching through a set of semantic Web services in order to find a match with a user query consisting of keywords. By specifying the search goal using keywords, end-users do not need to have knowledge about semantic languages, which makes it easy to express the desired semantic Web services. For matching keywords with semantic Web service descriptions given in WSMO, techniques like part-of-speech tagging, lemmatization, and word sense disambiguation are used. After determining the senses of relevant words gathered from Web service descriptions and the user query, a matching process takes place. The performance evaluation shows that the three proposed matching algorithms are able to effectively perform matching and approximate matching. <s> BIB002
Web service composition involves the combination of a number of existing web services to produce a more complex and useful service. The composition of web services is a topic that attracts the interest of researchers. It offers complex problems process ability even with simple existing web services while cooperating with each other. Web service composition is an important technology of SOA that is in a complex and distributed environment and still there are many potential problems BIB001 . One of main targets of Web service composition is reusing existing web services and composing them into a process. Such programs enable user to manually specify a composition of programs to perform a task, but it is already beyond the human capability to deal with the whole process manually. Despite all efforts, the web service composition still is a highly complex task and generally, the complexity comes from the following sources [2] : • First, the number of web services available on the Web is increasing dramatically during the recent years and can expect to have a huge repository of web services for searching. • Second, Web services can be created and updated on the fly, thus the composition systems needs to detect the updating at runtime. • Third, Web services can be developed by different organizations that use with different concept models for description of the web services. However, not exist unique language to defining and evaluation the Web services. BIB002 The variety of composition techniques can be classified according to two approaches. The first is syntactic composition based on syntactic description and other is semantic composition based on semantic description. We will see in this section several approaches for web service composition based on syntactic and web service composition based on semantic and we will discuss their limitations with regards to its requirements. The overall, the composition of web services can be done in a static or dynamic way that in the following is described. •