The following chapter focuses on the problem of the proper definition of non-functional properties and methods that may be applied in order to estimate their values. First of all, a reader is familiarized with the concept of non-functional properties and different views on the quality of Web services. Then, selected approaches to obtain values of non-functional properties are presented. The focus of attention is Web services profiling that seems to be one of the most promising methods to perform this task. The framework presented in this chapter was implemented and tested within the EU Adaptive Services Grid project.
Non-Functional Properties Of Web Services
To fully exploit the advantages of Web services technology, as indicated in the introduction section, their proper description is required. The common agreement is that a Web service should be represented by its surrogate, providing information on its functional (what a Web service does), non-functional (how it does it), and behavioural characteristics (which parties are involved in the process of service provisioning). However, before the initiatives in the area of Web services description are presented, differences between a service and a Web service, being crucial for our further discussion, need to be mentioned.
A service is usually defined as a provision of value in some domain (Preist, 2004) or seen as a business activity that often results in intangible outcomes or benefits (Baida, Gordijn, Omelayenko, & Akkermans, 2004). Let us consider an example of a person who wants to buy a book on knowledge representation published by Springer. The service this person is looking for is the provisioning of books with the specified constraints. A provision is in fact independent on how the supplier and provider interact (Lara & Olmedilla, 2005), that is, it does not really matter at this point whether the requester goes to a bookshop or uses the Amazon.com portal to buy the book of interest.