Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

Jan Hidders wrote:
> Jon Heggland wrote:
> > In article <0dBwe.133168$ut1.7226423_at_phobos.telenet-ops.be>,
> > jan.hidders_at_REMOVETHIS.pandora.be says...
> >
> >>>Yes. I know how to draw lines on a paper, but how do you do it on the
> >>>logical level (if there is such a thing)? But it seems you answer that
> >>>further down.
> >>
> >>Ok, but just to be sure let me answer it a bit more. It is quite easy to
> >>come up with a formal description of the syntax of such a data model,
> >>and it is also very easy to formally describe what drawing such edges
> >>exactly means, including any constraint that might be included in the
> >>notation.
> >
> > Do you have any examples apart from ORM? (What are the operators of ORM,
> > by the way?)
>
> Sure. FDM, IFO, LDM, HERM and even for subsets of UML class diagrams
> there are formalizations.
>

What's the (a) formalism for the FDM comparable to the RM (the FDM structure/the FDM algebra/FDM constraint definitions). Daplex does not quite cut it as an 'algebra'.

Now, IFO, as far as I remember, deals only with the structural part, namely, directed graphs representing 'atomic objects', 'constructed objects', etc. No algebra/data manipulatation and no constraint definition was suggested at the time.

Do not know about the rest of the bunch but wonder whether the triple <structure, algebra, constraints> has been defined for at least one of the abbreviations cited.

> For query languages for ORM see for example
> http://www.orm.net/queries.html or the work by Arthur ter Hofstede et al
> http://citeseer.ist.psu.edu/70483.html and if you give me a week I can
> invent two more myself. :-) Really, why do you think coming up with such
> a language would be a problem?

I tried to read one of the articles you've referenced (http://www.orm.net/pdf/ER96.pdf, "Conceptual query language"), but quickly stumbled over the words "semantic" and "conceptual". E.g. "ORM [...] exposes semantic domains as conceptual object types". What's a "semantic domain" ? How's it different from just a "domain" ? Or, what's a "conceptual object type" and how is it different from just an "object type" ? Is the article for real, or the words it uses are as redundant as the 'return' we discussed earlier ? Assuming "semantic domain" and "conceptual data type" roughly correspond to "domain" and "data/object type" respectively, the phrase "ORM [...] exposes semantic domains as conceptual object types" does not make much sense because "domain" and "data type" *are* the same thing unless the authors use some kind of private vocbulary in which case it would have been nice if they cared to share the vocabulary with their readers.

>
> No. In ORM NOLOTs are abstract. It is more correct to say that the RM is
> basically ORM restricted to LOTs. A very grave and crippling restriction
> indeed.

What does NOLOT being 'abstract' mean ?

What's a LOT formal definition other than just:

"Lexical Object Types (LOTs) are represented by a dotted circle. NOLOTs represent entity types for example (person) while LOTs represent their attributes for example (street). "

Thank you.

vc Received on Sat Jul 02 2005 - 05:18:27 CEST