On March 21, 2007, the OSOA Collaboration released the first version of specification. The specifications said that an application designed with SCA should have:
Decoupling of application business logic from the details of its invoked service calls
Target services in a multitude of languages including C++, Java, COBOL, and PHP as well as XML, BPEL, and XSLT
The ability to work with various communications constructs including one-way, asynchronous, call-return, and notification
The ability to "bind" to legacy components or services, accessed normally by technologies such as Web Services, EJB, JMS, JCA, RMI, RPC, CORBA and others
The ability to declare the quality of service requirements, such as security, transactions and the use of reliable messaging
Service Data Objects is a technology specification for data access
Disadvantages:
Specification does not address performance of SOA applications, which continues to be a detractor of adoption.
Focusing on portability, making it vulnerable to repeating CORBA's mistakes.
SCA was said to provide interoperability through an approach called "Activation". It is the method that provides the highest degree of component autonomy, compared to older "mediation" or "Invocation" method used in JCA, as explained by an architect at SAP.
Artifacts
The SCA Assembly Model consists of a series of artifacts, which are defined by elements contained in XML files. An SCA runtime may have other non-standard representations of the artifacts represented by these XML files, and may allow for the configuration of systems to be modified dynamically. However, the XML files define the portable representation of the SCA artifacts. The basic artifact is the composite, which is the unit of deployment for SCA and which holds services that can be accessed remotely. A composite contains one or more components, which contain the business function provided by the module. Components offer their function as services, which can either be used by other components within the same module or which can be made available for use outside the module through Entry Points. Components may also depend on services provided by other components — these dependencies are called references. References can either be linked to services provided by other components in the same module, or references can be linked to services provided outside the module, which can be provided by other modules. References to services provided outside the module, including services provided by other modules, are defined by External Services in the module. Also contained in the module are the linkages between references and services, represented by wires. A component consists of a configured implementation, where an implementation is the piece of program code implementing business functions. The component configures the implementation with specific values for settable properties declared by the implementation. The component can also configure the implementation with wiring of references declared by the implementation to specific target services. Composites are deployed within an SCA System. An SCA System represents a set of services providing an area of business functionality that is controlled by a single organization. As an example, for the accounts department in a business, the SCA System might cover all financial-related functions, and it might contain a series of modules dealing with specific areas of accounting, with one for customer accounts and another dealing with accounts payable. To help build and configure the SCA System, Composites can be used as component implementations, in the same way as Java classes or BPEL processes. In other words, SCA allows a hierarchy of composites that is arbitrarily deep – such a nested model is termed recursive. The capture and expression of non-functional requirements, such as security, is an important aspect of service definition, and affects SCA throughout the life-cycle of components and compositions. SCA provides the Policy Framework to support specification of constraints, capabilities and Quality of Service expectations, from component design through to concrete deployment.
After several years of incubation under an informal industry collaboration, early implementations of the specification are now coming to market. The collaboration partners indicated that formal industry standardization would be the appropriate next step and announced their intentions in March 2007. The chosen Standards Development Organization is the OASIS organization, and a new OASIS Member Section has been established. Charters for six new Technical Committees have been submitted to OASIS and a Call for Participation for Technical Committee members has been issued within the OASIS organization. The Technical Committees planned to start their work in September 2007. Participation in these OASIS SCA TCs remains open to all companies, non-profit groups, governments, academic institutions, and individuals. Archives of the work will be accessible to both members and non-members, and OASIS will offer a mechanism for public comment.
