Chapter 6. Creating the Conceptual Design

Terms you'll need to understand:

• Object Role Modeling (ORM)

• Value constraints

• Facts

• Set-comparison constraints

• Uniqueness constraints

• Subtype constraints

• Ring constraints

• Conceptual design model

Techniques you'll need to master:

• Transforming external information into elementary facts

• Applying population checks to fact types

• Identifying entities in a conceptual model

• Applying constraints to a conceptual model

• Validating the conceptual design model

Object Role Modeling (ORM) attempts to illustrate a system with graphical images. Other elements of a system's conceptual design provide the accompanying textual documentation. What you are documenting is data, procedures, and system behaviors. The end product of this phase is used in modeling the system in the subsequent phases. Models to be derived from the conceptual model include an Entity Relationship (ER) database model, a hierarchical system model, a network architecture model, an object-oriented applications model, and others.

There are many perspectives to ORM modeling, and to think of a system from solely a data perspective is a somewhat narrower view than you should have at this stage. In the previous chapter, you took a look at many other aspects of a system besides that of the data aspect. All these elements need to be modeled, as the system as a whole begins to become closer to what will actually be deployed. Still, at this stage you are still talking about conceptualization and theorythoughts and notions of what the system should be. It is important to be looking toward the system's future and, at the same time, be willing to adjust the picture and be open to the many possibilities the system might evolve into.

As with data modeling, which is discussed in Chapter 8, "Creating the Logical Data Model," you are focusing on the elements of the system, the data these elements use, and the relationships between the elements. It is truly at this stage that you pull information out of the interviews and turn it into the factual elements needed in the finished system.