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logical and physical modeling

  • January 20, 2003 at 8:59 pm

    #80183

    Hi everybody!

    Could somebody explain me or send me a link about the difference between logical and physical modeling of a DB.

    I know that the logical data model includes definition of the tables, their attributes and their constraints, defintion of the relationships between entities (tables) and the constraints on those relationships.

    Till here, everything is fine. What about the physical?

    Thanks a lot,

    Durug

  • January 20, 2003 at 10:13 pm

    #446820

    You've already got the hard part with the logical model. The Physical model is the database representation of the logical model. It defines how the entities and attributes map into an actual database schema.

    The physical model can also be geared towards performance and tuning issue for particular database platforms. Such as when views are used, etc...

    Thanks

    Phill Carter

    --------------------
    Colt 45 - the original point and click interface

  • January 20, 2003 at 11:26 pm

    #446821

    As far as I know and what we have followed for some time is to decide the Tables and the Attributes in each table and their relations with other tables under Logical design as you have already mentioned, and the Physical part usually involves the Data types to be used for the columns and their size estimates. Thus, also arriving at the size estimates of the database. Correct me if I am wrong...

    Cheers

    Arvind


    Arvind

  • January 21, 2003 at 4:32 am

    #446832

    A logical model has no ties to an actual database implementation. Column datatypes f.e. are implementation neutral. A logical model can contain heritage and ISA-relations and so forth.

    A physical model is the logical model translated to an actual db-implementation, like MySql, DB2 etc.

    There are tools for this, see

    Sybase/PowerDesigner

    CA/ERwin

    Mike Nicewarmer has a good site:

    http://www.datamodel.org

  • January 21, 2003 at 12:32 pm

    #446899

    Agree with the previous post.

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