4.4 Pattern Profiles

Each of the patterns in this catalog is described using the same profile format and structure based on the following parts:

•     Requirement

•     Icon

•     Summary

•     Principles

•     Architecture

•     Problem

•     Solution

•     Application

•     Impacts

•     Relationships

The following sections describe each part of a pattern profile individually.

Requirement

A concise, single sentence statement that presents the fundamental requirement addressed by the pattern in the form of a question. Every pattern description begins with this statement.

An example of a requirement statement:

How can a service be designed to minimize the chances of capability logic deconstruction?

Note that the left inside cover of this book lists the patterns together with their respective requirement statements.

Icon

Each pattern description is accompanied by an icon image that acts as a visual identifier.

An example of a pattern icon:

The icons are displayed together with the requirement statements on the inside front cover of the book.

Summary

Following the requirement statement, a summary table is displayed, comprised of statements that collectively provide a concise synopsis of the pattern
for quick reference purposes.

The following parts of the profile are summarized in this table:

•     Problem

•     Solution

•     Application

•     Impacts

Additionally, the profile table provides references to related service-orientation design principles and service-oriented architectural types via the following sections:

•     Principles

•     Architecture

The architectural types are described in Chapter 3 and to learn more about the design principles, visit SOAPrinciples.com.

The parts of the pattern description not represented in the summary table are the Relationships and Case Study Example sections.

Problem

The issue causing a problem and the effects of the problem are described in this section, which is often accompanied by a figure that further illustrates the Òproblem state.Ó It is this problem for which the pattern is expected to provide a solution.

Solution

The design solution proposed by the pattern to solve the problem and fulfill the requirement. Often this is a short statement accompanied by a diagram to concisely communicate the final solution state. ÒHow-toÓ details are not provided in this section, but are instead located in the Application section.

Application

This part is dedicated to describing how the pattern can be applied. In can include guidelines, implementation details, and sometimes even a suggested process.

Impacts

Most patterns come with trade-offs. This section highlights common impacts and requirements associated with the application of a pattern and may also provide alternatives that can be considered.

Note that these consequences are common but not necessarily predictable. For example, issues related to performance requirements are often raised; however, these issues may not impact an environment with an already highly scalable infrastructure.

Relationships

The use of design patterns can tie into all aspects of design and architecture. It is important to understand the requirements and dependencies a pattern may have and the effects of its application upon other patterns. This section is therefore dedicated to documenting key pattern relationships.

The content in this section is not exhaustive in that not all possible relationships a given design pattern can have are covered. This section highlights key relationships only, with an emphasis on how patterns support or depend on each other.