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Enterprise Service Computing From Concept to Deployment_6

Tham khảo tài liệu 'enterprise service computing from concept to deployment_6', kinh doanh - tiếp thị, quản trị kinh doanh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 162 Dubray agement of all these systems overrun the IT budget. Unfortunately even today new technologies appear such as the AJAX Garret 2005 pattern to develop the next generation ofWeb applications that do not seem to be concerned by the development of modular and composable assets. Even worse AJAX specifies an architecture in which the controller can be implemented either on the client browser within the AJAX engine or within the service-side systems. It is likely that most applications will operate in mixed mode creating assets that cannot be reused easily. Service Orientation In the last couple of years the industry has heavily marketed a series of new principles for designing modular enterprise systems under the name of service-oriented architecture and based on a set of platform-neutral open standards commonly referred as the Webservices technology stack Papazoglou 2005 . The objective of service orientation is to enable autonomous software or hardware agents to be assembled and participate in complex connected systems that perform units of work cooperatively. Agents expose a contract of which the unit of definition is called a service. A service interface defines the messages exchanged by the agent to perform its work. The message exchanges are grouped in operations. By extension these agents are called services. Agents interact as peers by exchanging messages to initiate work send notifications synchronize their state and request and send information. Service interfaces differ from object interfaces because they contain also the outbound operations in addition to the inbound ones explicitly specifying the entire contract they rely on to perform their work. These interfaces may be discovered manually or automatically in a registry. Service interfaces are often qualified by policies that specify the service capabilities. These policies are used to form agreements when two or more services are assembled to perform a unit of work. As we will see in the .