16-01-2013, 12:20 PM
Service Oriented Architecture
Service Oriented.ppt (Size: 1.57 MB / Downloads: 31)
Web services - Framework
The Web services framework is characterized by:
an abstract (vendor-neutral) existence defined by standards organizations and implemented by (proprietary) technology platforms
core building blocks that include Web services, service descriptions, and messages
a communications agreement centered around service descriptions based on WSDL
a messaging framework comprised of SOAP technology and concepts
a service description registration and discovery architecture sometimes realized through UDDI
a well-defined architecture that supports messaging patterns and compositions a second generation of Web services extensions
Service descriptions (with WSDL)
Abstract description
An abstract description establishes the interface characteristics of the Web service without any reference to the technology used to host or enable a Web service to transmit messages. By separating this information, the integrity of the service description can be preserved regardless of what changes might occur to the underlying technology platform.
portType, operation, and message
The parent portType section of an abstract description provides a high-level view of the service interface by sorting the messages a service can process into groups of functions known as operations.
Each operation represents a specific action performed by the service. A service operation is comparable to a public method used by components in traditional distributed applications.
Much like component methods, operations also have input and output parameters. Because Web services rely exclusively on messaging-based communication, parameters are represented as messages. Therefore, an operation consists of a set of input and output messages.
Service description advertisement and discovery
The sole requirement for one service to contact another is access to the other service's description.
As the amount of services increases within and outside of organizations, mechanisms for advertising and discovering service descriptions may become necessary.
For example, central directories and registries become an option to keep track of the many service descriptions that become available.
These repositories allow humans (and even service requestors) to:
locate the latest versions of known service descriptions
discover new Web services that meet certain criteria
Business service layer
Business service layer abstraction leads to the creation of two further business service models:
Task-centric business service A service that encapsulates business logic specific to a task or business process. This type of service generally is required when business process logic is not centralized as part of an orchestration layer. Task-centric business services have limited reuse potential.
Entity-centric business service A service that encapsulates a specific business entity (such as an invoice or timesheet). Entity-centric services are useful for creating highly reusable and business process-agnostic services that are composed by an orchestration layer or by a service layer consisting of task-centric business services (or both).