Section 17.4. Contracting


17.4. Contracting

Even after Web services are found that provide all operations required and support interactions in the order expected, additional kinds of matchmaking might be necessary based on the operational quality of services expected. For example, certain operations have to participate in transactions, some messages exchanged must be transported reliably, and other messages must be encrypted. The corresponding properties can be associated with port types, operations, or messages via policies (see Chapter 7, "Web Services Policy") and these policies are used to perform the corresponding matchmaking.

In many situations, additional requirements must be met. For example, when a requester is interested in a long-term relationship with a provider, you need to consider average response time of the performing operations, the availability of the service, and so on. These kinds of requirements are specified as service-level objectives. This might include the negotiation and specification of payments to be made by the requestor when all service objectives are met, as well as penalties to be paid by a provider if certain objectives are not met. All of this information is part of a contract that covers the interaction between the requester and the provider. Such a contract can even be negotiated automatically ([Dan 2004], [WS-Ag]).

Contracting is also a key prerequisite for the timely and flexible provision and consumption of services as part of the business processes of an organization, either within or across organizational boundaries [Rappa 2004]. It will very likely have a significant impact in the coming years. The possibility of a business process crossing an organizational boundary clearly raises the need to review the relation between service provisioning and service consumption as a business relationship, with all the complexity such a relationship entails: matchmaking, information exchange, negotiation, contract generation and signing, dynamic creation of different service configurations and their instantiation, service provision/consumption, monitoring of contract execution, relationship termination, evaluation, and of course, arbitration in case of dispute.



    Web Services Platform Architecture(c) SOAP, WSDL, WS-Policy, WS-Addressing, WS-BP[.  .. ] More
    Web Services Platform Architecture(c) SOAP, WSDL, WS-Policy, WS-Addressing, WS-BP[. .. ] More
    ISBN: N/A
    EAN: N/A
    Year: 2005
    Pages: 176

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