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

Silverston c03.tex V2 - 11/21/2008 2:59am Page 80

80 Chapter 3 ■ Using Roles: How Parties Are Involved

Synopsis

In this section you saw that the Level 1 Contextual Role Pattern is a useful

pattern for showing the scope of all the roles for a well-defined static entity.

Each of the roles was shown individually as attributes of the entity, and each

had a definition. The significance of this pattern is as a way of illustrating the

roles that are related to an entity in a very easy to understand modeling style.

This pattern helps to start the data modeling effort in a very understandable

way, capture common contextual role terminology, and show the scope of the

contextual roles in relation to an entity.

In this section you also saw that people and organizations can play more

than one contextual role at the same time or over time. We see in Table 3-1,

‘‘Una Corr’’ in one project played the project lead role and in another played

the project worker role, which can lead to data integrity issues because the

same party’s information can be maintained redundantly and inconsistently.

Some roles may be defined exclusively as organization or people contextual

roles. For example, project worker was described as ‘‘a person who performs

or is assigned to activities on a particular PROJECT.’’ The weakness here is that

the definition states that the role is a person role but the data model does not

enforce this. To some ...