Sample IDEF1X Modeling Methodology

Sample IDEF1X Modeling Methodology

CA ERwin DM was developed to support the IDEF1X and IE modeling standards. The use of various levels of models within the IDEF1X method can be very helpful in developing a system. General model levels are outlined in the IDEF1X standard and are presented next. In practice, you may find it useful to expand or contract the number of levels to fit individual situations.

The model levels generally span from a very wide but not too detailed view of the major entities that are important to a business, down to a level of precision required to represent the database design in terms understandable by a particular DBMS. At the very lowest level of detail, models are technology dependent. For example, a model for an IMS database looks very different from a model for a DB2 database. At higher levels, models are technology independent and may even represent information, which is not stored in any automated system.

The modeling levels presented are well suited to a top-down system development life cycle approach, where successive levels of detail are created during each project phase.

The highest level models come in two forms:

Entity Relationship Diagram (ERD)

Identifies major business entities and their relationships.

Key-Based (KB)

Sets the scope of the business information requirement (all entities are included) and begins to expose the detail.

The lower level models also come in two forms:

Fully-Attributed (FA)

Represents a third normal form model which contains all of the detail for a particular implementation effort.

Transformation Model (TM)

Represents a transformation of the relational model into a structure, which is appropriate to the DBMS chosen for implementation. The TM, in most cases, is no longer in third normal form. The structures are optimized based on the capabilities of the DBMS, the data volumes, and the expected access patterns and rates against the data. In a way, this is a picture of the eventual physical database design.

DBMS Model

The database design is contained in the DBMS Model for the system. Depending on the level of integration of the information systems of a business, the DBMS Model may be a project level model or an area level model for the entire integrated system.

Chapter 2: Information Systems, Databases, and Models 15