*Editor’s note: For Part I of this article, click here: http://www.ebizq.net/topics/soa/features/6228.html

The patterns mentioned in Table 3 below are some of the patterns for SOA and SOI that have been "mined" from a variety of projects:

Each point in the diagram below may be justifiable or appropriate for a given situation, and going to the right side of the spectrum may not always be the right thing to do or solution to adopt. The progression represents an increasing degree of maturity and the need for greater sophistication to handle increasing complexity and overcome new and more daunting business challenges as supported by IT.

The following sections will introduce some of the fundamental patterns that form the foundation of the pattern language for SOA/SOI. By "fundamental", I mean that clients tend to run into the problems associated with these patterns first and foremost and need to solve them in order to make progress in their path to SOA. SOA is a journey of gradual, small transformations that increasingly decouple service descriptions from service implementations offered by multiple service providers. The solutions below are descriptions of how these issues have been recurrently solved and may serve as a pattern to help you on your next project. Like any other pattern, these must also be adapted to fit the context and the forces that shape your individual problem space: the tradeoffs and considerations of your project, whether organizational or technical, make a difference, and you can determine if you need to skip a step from one pattern to another or to partially implement the pattern.

Discussion and context for the patterns

Most organizations have multiple heterogeneous backend legacy systems, only some of which are funded to be enabled to participate in an SOA. Often an organization is divided into lines of business that each may own a portion of the overall suite of systems without having control over a horizontal set of applications that supports a single business process. Thus, a business process may cut across multiple business lines with various system owners being involved. Each system will support (be used to update or create) one part of the business process. Each participant in the end-to-end process may not be in a position to fund or comply with an SOA migration or do so in a timely fashion. Thus, it is important to note that one organizational unit?s decision to migrate its capabilities to SOA does not imply that other line of business or the partners that provide dependent functionality.