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Applied Information Studies

published 20 Oct 1995 : 01 Jan 1996 updated


PowerDesigner Conceptual Data Model

PowerDesigner separates its data modeling process into two layers of abstraction: the Conceptual Data Model (CDM) and the Physical Data Model (PDM). The CDM employs elements of both conceptual and logical modeling to represent a formal data structure in graphics, formatted data, and text. The CDM captures entities, relationships, attribut, entity identifiers, and rules governing the various defined objects. This generalized model can be projected into a PDM targeting any of the 40+ DBMS products which PowerDesigner supports.

There are some conceptual and logical design features missing from the CDM (e.g.: an exclusive "or" relationship set; subset inclusion and exclusion). Some features which we classify as logical are provided in the PDM (e.g.: uniqueness via indexes, referential integrity options; foreign key transferability).

One could argue that these issues should and could be more abstract, i.e., "logical", rather than dependent on the choice of database product in the physical model. We have in fact suggested this to Powersoft and it is on the list of enhancement suggestions. Meanwhile, we find it is most comfortable and productive to learn and accept the PowerDesigner CDM on its own terms and definitions, rather than struggling to fit it into some arbitrary framework.

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Copyright © 1995 Applied Information Science International; 20 Oct 1995