Taxonomy and synthesis of Web services querying languages

Most works on Web services has focused on discovery, composition and selection processes of these kinds of services. Other few works were interested in how to represent Web services search queries. However, these queries cannot be processed by ensuring a high level of performance without being adequately represented first. To this end, different query languages were designed. Even so, in the absence of a standard, these languages are quite various. Their diversity makes it difficult choosing the most suitable language. In fact, this language should be able to cover all types of preferences or requirements of clients such as their functional, nonfunctional, temporal or even specific constraints as is the case of geographical or spatial constraints and meet their needs and preferences helping to provide them the best answer. It must also be mutually simple and imposes no restrictions or at least not too many constraints in terms of prior knowledge to use and also provide a formal or semi-formal queries presentation to support their automatic post-processing. To help assisting developers in their choices and also identifying the criteria that should satisfy a standard language, this article presents a taxonomy of different classes of query languages designed to be able to express Web services queries. An illustrative example is also given to illustrate clearly the different query representations that can be offered by these languages classes. A comparative study is eventually established to allow to reveal the advantages and limitations of various existing languages in this context. It is a synthesis of this category of languages discussing their performance level and their capability to respond to various needs related to the Web services research and discovery case. The criterions identified at this stage may, in our opinion, constitute then the main pre-requisite that a language should satisfy to be called perfect or to be a future standard. Keywords-Web service ; query ; query languages ;