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

"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?

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

are there any other types of constraint? non-semantic, maybe?

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

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

no, i don't think so

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

yeah, that's gorgeous, which book/website did you lift that out of?

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!

Data Modeling Essentials, Graeme C Stinson, Graham C Witt

Thanks again

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

Ravi