Re: Multiple specification of constraints

"ben brugman" <ben_at_niethier.nl> wrote in message news:40436e17$0$268$4d4ebb8e_at_read.news.nl.uu.net...
>
> "Marshall Spight" <mspight_at_dnai.com> wrote in message
> news:%kJ0c.94816$4o.117703_at_attbi_s52...
> > "ben brugman" <ben_at_niethier.nl> wrote in message
> news:4043049f$0$269$4d4ebb8e_at_read.news.nl.uu.net...
> > >
> > > And most discussions in this 'newsgroup' only concern constraints
> > > which do apply to the database.
> >
> > It's a database theory newsgroup, so this should not be a surprise.
> >
> >
> > > (This is the set of data which is
> > > still present, after the machine is shut down.
> >
> > Ack! That's not a good definition! RDBMSs are primarily about data
> > management, not persistence. They happen to be a good place to
> > implement persistence as a service, but there are other things that
> > can do that too just as well. But those things can't do data management.
> >
>
> The 'definition' concerns the database, not the RDBMS or not the
> (RDBMS-)instance. So for the database the definition 'holds'.
> For a RDBMS or a (RDBMS-)instance you are correct. The database
> part is only the persistence part which can be recovered after a crash.
> (But I must admit that I often use the term database where RDBMS should
> be used. In the above case I didn't).
>
> > The idea that databases are primarily about persistence is toxic myth.
> > You can have persistence without data management, and you can
> > have data management without persistence.
>
> Databases are about persistence.

A database is a set of facts. It might persist, and it might not.

> > It is important to differentiate between application constraints and
> > data constraints. Something that is only necessary for one particular
> > application and not for others is not a data constraint, and does
> > not have the same centralization requirements.
> >
>
> Constraints are requirements of the 'user', or the 'one' who is defining
> the system.

Nope. They are limitations imposed on the user to keep the fallible from doing what they do best. Received on Tue Mar 02 2004 - 05:20:22 CET