The use of a single service is usually not sufficient to implement complex business logic. Then, with the goal of completing the promises of the proposition of service-oriented architecture, web services must be divided in order to build larger applications and significant complexity. As noted earlier, implementing complex systems based on the use of simpler services facilitates development work and promotes reusability.
Various technologies can be used in the field of composite services (not necessarily web services). However, a strong trend is driving the research and implementation efforts for the implementation of compound web services. Some factors contributing to this trend:
Web services have well-defined interfaces. Through the WSDL standard, they have standardized interfaces, from which the service functional information can be extracted without too much difficulty;
Web services are standardized (described in WSDL invoked through XML in SOAP messages);
Traditional languages were not developed with the composition in mind. Thus, for their use, other aspects must be evaluated, for example, data conversion, message creation and dynamic binding components during compounding. The design itself would have a longer duration because the analysis (and deployment) of these aspects.
The web services composition is concerned with the internal implementation of the operations of the services. The development of a composite service of a company is kept private, even if other external web services are used. And, most importantly, the execution of the composite service is transparent to the customer, ie, they do not know (and do not need to know) that a service actually invokes several other to produce the required result.
One of the most important properties of a web services composition is that the composition is also a web service. This property is of fundamental importance in the SOA context, in that the web services compounds can be used as a simple web services participating in compositions and business logic more complex themselves.
Initially, it is planned to a more detailed study of security-related aspects in the context of the composition. It has been placed as the critical factor for the adoption of such technologies; this way, a more differentiated treatment should be given the specification and use, regardless of the environment and the size of the project to which this composition is attached.