The Data Model Resource Book, Volume 3: Universal Patterns for Data Modeling

Silverston c06.tex V2 - 11/21/2008 3:09am Page 269

Level 4 Status Pattern 269

Level 4 Status Pattern

The Level 4 Status Pattern is even more flexible than any of the preceding

patterns in this chapter. We consider it a ‘‘plug-and-play’’ type pattern. What

we mean by this is that with this pattern any ENTITY that needs to maintain

statuses just needs to plug itself into this structure, without adding any

new entities or attributes (except a foreign key). When a new entity needs

to capture statuses, all t hat is necessary is to create a relationship from the

ENTITY to STATUS APPLICATION and include a foreign key in the STATUS

APPLICATION entity.

Why Do We Need This Pattern?

This pattern is quite similar to the Level 3 Pattern, but it differs in one significant

way: instead of having an individual ENTITY STATUS connected to STATUS

TYPE, a single consolidated entity called STATUS APPLICATION supports all

relationships to the STATUS TYPE entity. This is almost the equivalent of an

interface in programming. In other words, if any new or existing entity needs

to maintain status information, all you need to do is attach to the interface

STATUS APPLICATION by creating a relationship to it. This is very useful for

enterprises that have a very dynamic data environment and that want to have

a standard, modular approach for maintaining status data.

How Does This Pattern Work?

Figure 6-8 illustrates the pattern.