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  1. #1
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    Mar 2006
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    Semantic Constraint

    Hi all:

    Just wondering if someone could help me with the following: I have been asked to describe one limitation a semantic constraint can impose, and so far I have come up with the following: "Semantic constraints can prohibit what changes to data are allowed", "And/or without an assigned semantic constraint, data collated or input wouldn’t have any meaning, thereby rendering any data/string search ineffective".

    Could someone please advise me if I’m either on the right or wrong lines?

    Many thanks

    Oliver

  2. #2
    Join Date
    Apr 2002
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    "prohibit what changes are allowed" doesn't make sense -- perhaps it should say "enforce what changes are allowed"

    the second one, well, how should i put this, makes even less sense

    in your words, what is a semantic constraint?
    rudy.ca | @rudydotca
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  3. #3
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    Mar 2006
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    okay:

    Well a semantic constraint can used for restricting data in a database, thus one can then give users error msg like: "Integrity Constraint Violation", when an attempt is made to enter an invalid entry, therefore could the above example be used to describe a limitation a semantic can impose?

    Thanks

    Oliver

  4. #4
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    are there any other types of constraint? non-semantic, maybe?
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  5. #5
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    Mar 2006
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    Hi:

    Just need to know whether the above descriptive was a good enough example of the type of limitation a Semantic Constraint can impose?

    Thanks

  6. #6
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    you mean the "data wouldn't have any meaning" statement

    no, i don't think so
    rudy.ca | @rudydotca
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  7. #7
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    Mar 2006
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    Okay,

    I alternatively have the following simplified defention of my own for "Semantic Constraint", maybe this will be more acceptable: "A semantic constraint defines the acceptable value domain for an attribute or a consistency relationship between attribute values".

    Does this then make more sense?

    Thanks

    Oliver

  8. #8
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    yeah, that's gorgeous, which book/website did you lift that out of?
    rudy.ca | @rudydotca
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  9. #9
    Join Date
    Mar 2006
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    lol

    The "Semantic" meaning was hidden deep within my Uni text book! I have just condensed the text to come up with a simplified definition. Right, now I glad I'm on the right track!

    Thanks for your help, very much appreciated.

    Oliver

    p.s you couldn't recommend any good relational database (Theory & Design) books could you? Mine appear very limited when it comes to advanced topics!

  10. #10
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    Apr 2002
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    Data Modeling Essentials, Graeme C Stinson, Graham C Witt
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  11. #11
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    Mar 2006
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    Thanks again

  12. #12
    Join Date
    Apr 2004
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    An excellent book is the one by Chris Date

    The title says it all. No database practitioner should be without it.

    Ravi

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