Re: MV Keys

Jon Heggland wrote:
> In article <1141387926.092588.82100_at_v46g2000cwv.googlegroups.com>,
> jog_at_cs.nott.ac.uk says...
> > A crucial point is that this is only true if the system offers a
> > mechanism to perform the decomposition. If it does not, then to the
> > system itself your compound datatype is a single value.
>
> Why is this crucial?

Because some appear to be missing this point, and hence confusing actually what a compound type is. A comma seperated string, for example, sitting in a relational database is hardly a compound type as far as the RM is concerned. It is merely a string. Perhaps you're still confusing a multi-attribute system with a system that supports compound data types?

>
> > This is the reason that nested relations is a valid approach within
> > traditional RM - a compound datatype with a mechanism for its
> > manipulation.
>
> That doesn't make sense to me. Compound attributes are valid if the
> system can decompose them, and if the system can't decompose them,
> they're not compound?

Yes. What about that doesn't make sense to you? In the system marshall is involved with I'm sure his list/set constructs will be provided with mechanism for their manipulation and for extraction of individual values.

> --
> Jon

All best, Jim. Received on Fri Mar 03 2006 - 19:55:32 CET