SOA Glossary

This glossary supports the following titles:

SOA: Principles of Service Design (ISBN: 01323 44823, Prentice Hall)

Service-Oriented Architecture: Concepts, Technology, and Design (ISBN: 0131858580, Prentice Hall)

Service-Oriented Architecture: A Field Guide to Integrating XML & Web Services (ISBN: 0131 428985, Prentice Hall)

For more information about this book series, visit: www.soabooks.com

design-time autonomy

Regardless of whether a service has control over its runtime execution environment, multiple service consumers will form design-time dependencies on it. This can restrict the ability to evolve a service in response to future change requirements. The level of freedom service owners have to make changes to a service over its lifetime can be referred to as design-time autonomy.

Once consumer programs programmatically bind themselves to a service’s contract, the service can no longer escape its obligation to that contract. We therefore automatically lose a degree of control over how the service could be evolved. However, given that baseline constraint, we can still strive to maximize the level of attainable design-time autonomy.

There are several aspects of SOA that drive the need for this quality:

• the ability to scale a service in response to higher usage demands

• the option to further modify or enhance a service’s hosting environment

• the freedom to augment, upgrade, or replace the technology of a service in response
to new requirements or a desire to leverage new innovations

All of these forms of design-time autonomy can be attained by applying the Service Loose Coupling principle to avoid negative forms of service coupling.