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

Silverston c03.tex V2 - 11/21/2008 2:59am Page 74

74 Chapter 3 ■ Using Roles: How Parties Are Involved

the quality of an ORDER may play a contextual role of ‘‘quality assur-

ance person’’ that doesn’t need to be declared as a declarative role.

Is this role significant within the context of the enterprise as whole?

If the answer is yes, the role is a declarative role. For example, the role

of CUSTOMER may be significant not only for specific transactions but

in general across the enterprise. Declarative roles may be used and built

upon using the contextual role patterns in this chapter. For example, a

CUSTOMER may be declared and then used to relate the CUSTOMER to

aparticularORDER.

Level 1 Contextual Role Pattern, Attributes

It is often common to see the specific roles associated with an entity captured

as attributes of that entity. For example, an ORDER may have the ship-to and

bill-to customers defined as attributes of that order. The names of the bill-to

and ship-to customers are captured in those attributes for an instance of a

specific order.

Why Do We Need This Pattern?

The Level 1 Contextual Role Pattern, Attributes, shown in Figure 3-1, provides

the most specific way to model contextual roles. The roles are maintained via

attributes for that particular entity. This pattern also provides a view of the

scope of all the roles for a particular piece of data. Also, it is surprising how

many data models; ...