THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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SCA is a standard programming model for abstracting business functions as components and using them as building blocks to assemble business solutions. An SCA component offers services and depends on functions that are called references. It also has an implementation associated it with it which is the business logic that can be implemented in any technology.
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The basic building block for SCA is a component. It is the abstraction of a given business function. A component is described with the following attributes:
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The implementation of a component can be in any language that is suitable for the user, for example BPEL for business processes or XSL-T for transformations or Ruby for scripting or pure Java. How the services, references, properties and intents are defined for an implementation is specific to that particular implementation type.
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As mentioned above, an SCA component may have zero or more references. Refrences in SCA define how SCA components invoke services. The relationship between a reference and a service is typically demonstrated through a line in a SCA diagrams and is referred to as a wire.
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An SCA composite consists of components, services, references, and wires that connect them. A composite is the unit of deployment for SCA.
A composite can be viewed as a component whose implementation is not code but an aggregation of one or more components co-operating to provide higher level services. Think of composite as a solution, for example a credit check composite may consist of multiple components that together perform the credit checking work. A composite can also be used within a larger solution, for example credit check can be part of a order processing composite. A composite has the same charactersitics as a component. It provides Services, has References to other dependencies, and can be configured using Properties and can have intent policies in just the same way as an individual components can. In thise case, attributes of some of the components that are embedded in the composite get 'promoted' and becom the attribute of the composite. In the example below, you see a calculator composite which consists of 5 components, a calculator service has references to four components:Add, Subtract, Multiply and Divide.
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The artifacts that make up a solution get packaged into what is called a contribution. A contribution can take a number of different forms. For example, it could be a jar file, or it could be a directory tree on the file system. A contribution can contain composites, java classes, BPEL processes, XSD files, wsdl files, etc. An SCA application can be divided into multiple contributions with dependencies between them. In general, some services depend closely on other services and it makes sense to package them together. If services are more independent it is best to package them separately so that they can be reused in different contexts. A contribution is a deployable unit. A solution may require multiple contributions that share artifacts and artifacts can be shared between (imported) between contributions.
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Contribution packages get contributed to what is called SCA domain which is the scope of adminstration at runtime. An SCA Domain represents a complete runtime configuration, potentially distributed over a series of interconnected runtime nodes and is a logical view of the running applications or a coherent grouping of components that are working together. An SCA Domain typically represents an area of business functionality controlled by a single organization. For example, an SCA Domain may be the whole of a business, or it may be a department within a business.
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A binding is used as a means of communication between services and handles the protocols. It defines with what communication method a service can be accessed with or with what communication method it can will access other services. There can be different types of bindings depending on technologies used to develop a solution. For example JMS binding, Webservices binding, Atom binding for web20 interaction, etc.
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An enterprise application requires control beyond the business functional capability which can include how security is handled in the enterprise or what transactional capability should be applied to services that are offered. SCA policies define the constraints or capabilities that get applied to services and their interaction. Two types of policies are defined in SCA.
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