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

Silverston c02.tex V2 - 11/21/2008 2:58am Page 47

Level 2 Declarative Role Pattern 47

Within the context of a relational model, this pattern has many weaknesses.

For example, this pattern may store redundant attributes. Data stored redun-

dantly can quickly create future data quality issues if not managed correctly.

The same person or organization may appear twice in two different declarative

roles. How do you reconcile them? It is difficult to see the whole picture of

a person or organization if they play many roles, and thus you are looking

at pieces of the person’s or organization’s data in different entities. This pat-

tern often helps us highlight the weaknesses of implementing this pattern to

business and technical stakeholders.

Finally, this pattern is most suited for illustrating information requirements

about declarative roles in a simple way. It is most useful in very well-defined,

static environments. If roles change, then implementation of this pattern leads

to a design that is not stable, because the underlying data structures will

probably require change.

Level 2 Declarative Role Pattern

It is often desirable to model declarative roles with flexibility, but still maintain

the specific nature of the pattern. By adding the PARTY entity to the pattern,

attributes that are related to people (e.g., first name, last name and date of

birth) and related to organizations (e.g., organization name ...