In the context of Enterprise Architecture (A.K.A. Systems or Organizational Architecture or Modeling) the term “Service” refers to a discretely defined set of contiguous and autonomous business or technical functionality. (This is not to be confused with Web Services which is just one way of implementing the automated aspects of a given business or technical service.) An Enterprise Architecture Team will develop the organization’s “Service” model first by defining the top level Business Functions. Once the Business Functions are defined they are decomposed into “Services” which represent the processes and activities needed to manage the assets of the organization in their various states. An example here would be the decomposition of the Business Function “Manage Orders” into “Services” such as “Create Order”, “Fulfill Order”, “Ship Order”, “Invoice Order”, “Cancel/Update Order”, etc.

A “Service” has a definition. This definition consists of:

1. An explicit and detailed narrative definition supported by a low (but not detailed implementation specific) level process model.
2. A set of performance indicators that address measures/performance parameters such as availability (when should members of the organization be able to perform the function), duration (how long should it take to perform the function), rate (how often will the function be performed over a period of time), etc.
3. A linkage to the organization’s information model showing what information the “Service” owns (creates, updates, and deletes) and which information it references and is owned by other “Services”.
4. A listing of known downstream consumers (other “Services” that depend upon its function or information) and the documentation of their requirements.