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Automatic Composition of Web services based on Functional Annotations Disclosure Number: IPCOM000028663D
Original Publication Date: 2004-May-26
Included in the Prior Art Database: 2004-May-26
Document File: 2 page(s) / 48K

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A method is proposed to provide the functional annotation of a Web service in the form of a communicating finite-state machine and to use this functional annotation within an automatic algorithm to compute the composition of Web services. The algorithm searches the space of finite-state machines to select Web services that form a composition, which can be executed to achieve an explicit goal or behavioral specification of a business process.

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Automatic Composition of Web services based on Functional Annotations

A Web service as it is defined in WSDL encapsulates a particular piece of software that can be invoked via the internet. WSDL is an XML-based language used to specify the location of the Web service and the operations (or methods) that it exposes. A Web service is characterized by a porttype, which is an element that specifies the operations and messages involved in interacting with the Web service. A WSDL specification only tells us something about the syntax of messages that enter or leave the piece of software that is encapsulated within the Web service. The functionality of a Web service needs to be described with some additional piece of information, either by some semantic annotation of what it does or by some functional annotation, how it behaves. Semantic annotations of Web services have been widely discussed in the Semantic Web community. By using pre-agreed ontologies, the meaning of a Web service and the messages it exchanges can be understood and used in a composition. Alternatively, a behavioral specification in the form of a state-machine can be used to describe the behavior of the piece of software encapsulated by the Web service. This approach is proposed here.

A Web service composition is usually created to implement a business process. One can describe the requirements for the composition by giving the goal of the business process or by describing its desired behavior.

The goal of the business process can be given by a so-called temporally extended goal using a temporal-logic formula. An example is "Eventually pay all bills by always complying to the agreed payment method."

Alternatively, the desired behavior of the business process can be specified using a finite-state machine.

An automatic composition process can now be used to compose Web services based on the functional annotations in the form of finite state machines. The correctness criterion can be stated: The composition must satisfy the temporally extended goal and/or the given behavioral specification of the business process in the form of a finite-state machine.

The correctness criterion is defined more precisely as follows:

1) The temporally extended goal is always true in all states on all execution paths of the Web servi...