Re: In an RDBMS, what does "Data" mean?

In message <40da0edf$0$48959$e4fe514c_at_news.xs4all.nl>, mAsterdam <mAsterdam_at_vrijdag.org> writes
>> Which is better. For the system to store information by default
>>which can be ignored if it is irrelevant, or for the analyst to be
>>forced to take every possible eventuality into account? After all,
>>EVERYONE is fallible :-)
>
>Are these really the only alternatives? Let me guess.
>Analysts usng a RDBMS have to be perfect to get it right,
>but MV automagically stores everything possibly relevant.

:-)

Analysts using an RDBMS have to be perfect to get it right, while MV does some of the work for the analyst without him even realising it ...
>
>>>> And even where R expresses an M-like view of the data, it contains
>>>>less INFORMATION, because R is unaware that it is expressing metadata.
>>>
>>> So now languages should be aware of what they are expressing.
>>> Why this mixing, IMO unnecessary confusing way of saying things?
>>>
>> Maybe because I'm not good at expressing myself clearly?
>
>Any other complaints about that? Not from me.
>I suggest that if MV does not convey all relevant data, MV is not
>good at expressing itself clearly.

I thought I was talking about me, not MV :-)
>
>> But let's go back to the "list or bag" thing. If both the MV and the
>>relational database contain the *same* data, then the MV version is
>>richer because it has retained any order that was there.
>
>Why not convey it explicitly, if it is relevant?
>
>> If the app wants a bag, it can ignore the order. But if the app
>>wants the original list, not only does the relational version have to
>>store more data, but it has to do more with it - it has to sort it
>>before handing it back to the app. The app needs to know that it's
>>supposed to be a list, and also has to know how to convert the set
>>back to an ordered list.
>> That's what I'm trying to express - a lot of stuff is implicit in
>>the MV approach, which you can ignore if you want. By explicitly
>>forcing this metadata into data, a relational app needs to "know" a
>>lot more to get the same result.
>
>All data expressible in R is expressible in M.
>True?

Yes. But if the *same* *data* is stored in both, then M can (normally) express more. (ie if order is not stored as data, then M can still express it.)

Cheers,
Wol

-- 
Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
HEX wondered how much he should tell the Wizards. He felt it would not be a
good idea to burden them with too much input. Hex always thought of his reports
as Lies-to-People.
The Science of Discworld : (c) Terry Pratchett 1999