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An Overview of Service-Oriented Architecture

Yet another benefit of WCF is that it is based on the design principles established by service-oriented

architecture (SOA). To be sure, SOA is a major buzzword in the industry, and like most buzzwords,

SOA can be defined in numerous ways. Simply put, SOA is a way to design a distributed system

where several autonomous 

services work in conjunction by passing messages across boundaries

(either networked machines or simply two processes on the same machine) using well-defined

interfaces.

In the world of WCF, these “well-defined interfaces” are typically created using actual CLR

interface types (see Chapter 9). In a more general sense, however, the interface of a service simply

describes the set of members that may be invoked by external callers. 

When WCF was designed, the WCF team did so by observing four tenets of SOA design princi-

ples. While these tenets are typically honored automatically simply by building a WCF application,

understanding these four cardinal design rules of SOA can help put WCF in further perspective. The

sections that follow provide a brief overview of each tenet.

Tenet 1: Boundaries Are Explicit

This tenet reiterates the fact that the functionality of a WCF service is expressed using well-defined

interfaces (e.g., descriptions of each member, its parameters, and its return values). The only way

that an external caller is able to communicate with a WCF service is via the interface, and the exter-

nal caller remains blissfully unaware of the underlying implementation details. 

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