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

"Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message news:xxBxe.135773$vq.7300203_at_phobos.telenet-ops.be...
> VC wrote:
>> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
>> news:eHrxe.135259$JD6.7251058_at_phobos.telenet-ops.be...
>>
>>>vc wrote:
>>>
>>>>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'.
>>>
>>>Why not? Because it has operations with side effects?
>>
>> An algebra is a set S together with operations on S.
>
> Then why did you put it between quotes?

Probably my use of quotes was incorrect. I wanted to express the idea that Daplex is not an algebra. Please ignore the quotes.

> Anyway, why do you want specifically an algebra? You don't need one for
> asking queries, not for defining views and you don't need one for query
> optimization, so why bother?

Please clarify whether tour are talking about the RM views and queries or about something else.

>
>>>>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".
>>>
>>>:-) Yeah, ORM people like to use those words a lot. I wouldn't worry too
>>>much about it. You can understand the query language w/o understanding
>>>what those words exactly mean.
>>
>> Can your response be interpeted as meaning that the article is
>> essentially non-sensical (we do not care what the words the authors use
>> mean) ?
>
> No, just that the specific meaning of those words is not essential for
> understanding the query language and that, since you seem an intelligent
> person you will probably pick up their meaning as we go along. Most of my
> students seem to manage it, so I don't see why you couldn't.

Well, apparently, I am not as smart as most of your students are. Please provide a definition of "conceptual object type".

>
>>>>What does NOLOT being 'abstract' mean ?
>>>
>>>That there is no value representation associated with non-lexical
>>>objects.
>>
>> OK. Firstly, why do we care about 'value representation' at all ?
>
> Because otherwise we couldn't indicate in an ORM schema that the name of a
> department is represented as a string.

Cannot we just use the notion of data type (aka domain) instead ? Also, what's the formal definition of LOT ?

Thank you.

vc
>
> -- Jan Hidders
Received on Sun Jul 03 2005 - 06:28:12 CEST