Re: Conceptual, Logical, and Physical views of data

David,

For that last remark I always think in 4 levels:

1. Conceptual model

2. Logical model

4. Logical Database model (actual database model "SQL model" *only*
abstracted from physical vendor implementation)

5. Physical model

Layer 4, could also be called 2a or 3b. It is a practical nessecity
because of non standard's within the DMBS field. Most information
practicioners do not see this extra level, they lump it either with the
pyisical model or the logical model. Either choice is bad, but
maintaining an extra model is dubbed to expensive by most, they usually
pick a vendor and don't worry about it.

IMO the usablility of this extra layer shows how good database vendors
are at screwing standards and trying to be as non compatible as
possible without actually denouncing SQL compliance.

DM Unseen
DM Unseen

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