Tutorials SOA Web ServicesThis is the simplest pattern and defines a 1-to-1 interaction between a pair of applications. These interactions may be complex, which might be broken down into multiple elementary interactions. The pattern addresses these connections. The following figure illustrates this pattern.
The connections may require the application of certain business rules such as data mapping rules, security rules, and so on. The connection may be message or call oriented. These are further classified as synchronous or asynchronous. Generally, the call-oriented connection is synchronous while the message-oriented connection is asynchronous—whether it is synchronous or asynchronous is decided by the integration needs.
In the case of an Extended Enterprise domain, the Exposed Direct Connection application pattern allows the applications to communicate directly across the enterprise boundaries. Thus, this can be applied only in the case of trusted patterns and requires a highly secure channel for communication across the enterprise boundary.
The Direct Connection application pattern maps perfectly into the SOA paradigm. There is a 1-to-1 connection between a service consumer and a provider. The services may be classified based on the functionality and QoS (Quality of Service). The connection rules may be modeled on these factors. A consumer may discover a desired service from the registry. Thus, the application of this pattern fits perfectly in the SOA domain.
The connection may be defined logically rather than physically. This result in creating a Service Bus, which is a subset of the Enterprise Service Bus discussed in an earlier chapter and covered in more depth in Chapter 6.
