Data Model Hierarchy

Concept:

In a large scale enterprise setting, any single data modeling target is likely to exist in a context of multiple layers of conceptual, logical, and physical models. So a "data model" is really a set of models, including perhaps an enterprise conceptual/logical umbrella, subject specific conceptual extensions, logical models fleshed out for the special needs of the subject, and one or more physical schemas for various target installations.

Navigation:

Click any object for a discussion of the general nature of that model type. Click the yellow background to go to the PowerDesigner modules page.

See Results

See also:

• Multiple PDM targets from one CDM

Issues:

Charlie Johnson

• Changes made at the PDM are not always remembered and are lost when generating a now CDM..
  
• We would like a CDM, when created from a PDM, to "remember" where it came from so it does not create duplicate PMD structures and related problems when generating the PDM.

Jeff Weeks

• The tool should maintain a separation between the conceptual and physical implementation.

Paul Ratkos

For me the word Enterprise would be my key issue.

• Along with this of course is the single point of entry into the logical enterprise and a single resulting schema physical regardless of the dbms. Dbms issues should be just that, the conceptual model is not defined based on dbms's and the physical schema is not defined based on dbms's. The physical schema targets dbms's and the unique characterics of one dbm's or another does not alter the physical schema. My point is that in an enterprise an object is defined once regardless of who uses or which dbms it is defined for. Single point of entry rather than and maintaining one enterprise model eliminates multiple entry that can and usually does result in error.

Sharon Getha

• We want the ability to view the model from different perspectives like from a subject area or process view.
  
• We feel that currently we have to create a logical that almost mirrors a physical so the physical is generated properly. It would be nice to be able to indicate things in the logical that won't be translated to the physical. ( I think that some of the training you provided on inheritance and some of the tricks you showed us in class should be more publicized. It appears in our environment that the physical tables look almost exactly like the logical model. Not much denormalization is done. I think they re-generate the conceptual models too much and depend on that regeneration to help sync the models and they're disappointed that the logical really isn't the logical representation they originally had.) This may be a training issue.
  
• Also, the ability to support current systems analysis by providing a specific field in PowerDesigner to show how to map the logical to the physical. This would support the process in which canonical synthesis is performed and also the conversion process. If this is a separate field in the metamodel, then reports can be generated for use in conversion and change analysis.

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