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In response to requests from customers and Independent Software Vendor (ISV) partners, BEA, Cape Clear, IBM, Interface21, IONA, Oracle, Primeton Technologies, Progress Software, Red Hat., Rogue Wave, SAP, Siemens, Software AG, Sun, Sybase and TIBCO are collaborating on specifications for building systems that use a Service-Oriented Architecture (SOA), which aim to provide developers with simpler and more powerful ways of constructing applications based on SOA. These specifications are published under royalty-free terms. You can learn more about how these specifications work together.
Service Component Architecture: Build systems using SOA
Service Component Architecture (SCA) is a set of specifications which describe a model for building applications and systems using a Service-Oriented Architecture. SCA extends and complements prior approaches to implementing services, and SCA builds on open standards such as Web services.
SCA encourages an SOA organization of business application code based on components that implement business logic, which offer their capabilities through service-oriented interfaces and which consume functions offered by other components through service-oriented interfaces, called service references. SCA divides up the steps in building a service-oriented application into two major parts:
- The implementation of servicecomponents which provide services and consume other services.
- The assembly of sets of components to build business applications, through the wiring of service references to services.
SCA emphasizes the decoupling of service implementation and of service assembly from the details of infrastructure capabilities and from the details of the access methods used to invoke services. SCA components operate at a business level and use a minimum of middleware APIs.
Figure 1. Service Component Architecture
SCA supports service implementations written using any one of many programming languages, both including conventional object-oriented and procedural languages such as Java™, PHP, C++, COBOL, XML-centric languages such as BPEL and XSLT, and also declarative languages such as SQL and XQuery. SCA also supports a range of programming styles, including asynchronous and message-oriented styles, in addition to the synchronous call-and-return style.
SCA supports bindings to a wide range of access mechanisms used to invoke services. These include Web services, Messaging systems and CORBA IIOP. Bindings are handled declaratively and are independent of the implementation code. Infrastructure capabilities, such as Security, Transactions and the use of Reliable Messaging are also handled declaratively and are separated from the implementation code. SCA defines the usage of infrastructure capabilities through the use of Policies, which are designed to simplify the mechanism by which the capabilities are applied to business systems.
SCA also promotes the use of Service Data Objects to represent the business data that forms the parameters and return values of services, providing uniform access to business data to complement the uniform access to business services offered by SCA itself.
The SCA specification is divided into a number of documents, each dealing with a different aspect of SCA. The Assembly Model deals with the linking of components through wiring. The Assembly Model is independent of implementation language. The Client and Implementation specification deals with the implementation of services and of service clients -- each implementation language has its own Client and Implementation specification, which describes the SCA model for that language.
The current SCA specifications are published at a version 0.95 level, indicating that the specifications are not in their final form. The specifications are published with the intent of getting feedback from the community in order to ensure that the eventual version 1.0 level of the specifications more fully meets the needs of developers and businesses.
Get the specification and related material
| Description | Date | Access method |
|---|---|---|
| The SCA specifications are available on the Open SOA Collaboration Web site at www.osoa.org. | November 2006 | HTML page |
| The specifications can be viewed and downloaded from the SCA Specifications page. | November 2006 | HTML page |
Get the whitepapers and sample applications
In addition to the specifications, read the whitepapers and sample application for additional information on the Service Component Architecture specifications, which are also available on the Open SOA Collaboration website in the SCA Resources page:
| Description | Date | Access method |
|---|---|---|
| SCA resources. | November 2006 | HTML page |
If you would like to contribute technical comments on this specification, please do so through the Feedback page on the Open SOA Collaboration website.
Open Source SCA runtimes and tools
- There is an open source project which provides a Runtime implementation of Service Component Architecture, which you can use to run SCA applications. This project is called Tuscany, currently under incubation at Apache. See the Tuscany Web site at Apache.
- There is also an Eclipse open source project which aims to provide tools to enable developers to build solutions using a service oriented architecture, which uses Service Component Architecture as its core model. This is the Eclipse SOA Tools Platform project. See the SOA Tools Platform (STP) Project Web site.
About the Open SOA collaboration
- The SCA and SDO specifications are currently being evolved by a collaboration of companies from across the industry, prior to eventual submission to a formal standards body. To learn more about the Open SOA Collaboration, please visit the home page of the OSOA website.
- If you would like closer involvement with the evolution of the specifications, you can join the OSOA Supporters group. Learn more about the OSOA Supporters.
- See the related Service Data Objects specification.
- Find hundreds of articles, tutorials and interactive tools on related topics in the SOA and Web services zone.
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Standards roadmap -- understand the impact and importance of standards and specifications for the development of SOA and Web services.
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Architecture: Build for the future -- visit the Architecture area on developerWorks and get the resources you need to advance your skills in the architecture arena.
