Re: MV counterexample

"Tony" <andrewst_at_onetel.net.uk> wrote in message news:c0e3f26e.0405060138.155c0074_at_posting.google.com... > "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message news:<c7bhb2$cha$1_at_news.netins.net>...
> > "Tony" <andrewst_at_onetel.net.uk> wrote in message
> > news:c0e3f26e.0405051133.1d896668_at_posting.google.com...
> > > "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message
> > news:<c7ana5$tag$1_at_news.netins.net>...
> > > > "Karel Miklav" <karel_at_inetis.spppambait.com> wrote in message
> > > > news:c7a9eg016dp_at_enews1.newsguy.com...
> >
> > > > > Data is actually just a SET of whatevers, the views could be more
or
> > > > > less structured. That's it.
> > > >
> > > > Well, it's good to have PROOF like that! But, what if a better
> > metaphor
> > > > for data is that is it is a tree?
> > >
> > > It isn't. In a tree everything is either the root or belongs to
> > > something (which belongs to something ... which belongs to the root).
> > > Clearly not ALL data fits that metaphor. Not even MOST data does.
> >
> > Let's just say that what is clear to you is also clear to me and accept
that
> > arguement. Then what if a di-graph is a better metaphor? What are your
> > criteria for determining what is the best metaphor for data modeling,
> > database design and/or implementation? --dawn

>
> I don't see much similarity with a di-graph either.  I'm not sure I'm
> looking for a metaphor for database design, I just want to DO database
> design.  I suppose if I were, major criteria would be simplicity and
> applicability to all kinds of data.  Data is a collection of facts,
> which is what makes predicates attractive (as a metaphor?): "Employee
> E1 works in Department D1 and earns salary S".  How would you di-graph
> that (and why)?

Just as you can show the di-graph for a set of web pages, you can design such a set using a di-graph as a model. Similarly, in your example, you can write down your predicate, then show that the department links to a predicate such as Department D1 has Budget Officer B1 and Name N1 and Employees EM1. This predicate as well as the first can link to a predicate about how Employee has First Name and Last Name.

I don't have a more rigorous discipline to point you to, but there are many web resources related to di-graphs or web site design using graphs.

Did that help? --dawn Received on Thu May 06 2004 - 15:41:57 CEST