Re: Conceptual, Logical, and Physical views of data

From: DM Unseen <dm.unseen_at_gmail.com>
Date: 30 Aug 2005 04:24:18 -0700
Message-ID: <1125401058.492949.200790_at_z14g2000cwz.googlegroups.com>


David,

For that last remark I always think in 4 levels:

  1. Conceptual model
  2. Logical model
  3. Logical Database model (actual database model "SQL model" *only* abstracted from physical vendor implementation)
  4. 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 Received on Tue Aug 30 2005 - 13:24:18 CEST

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