Re: Domain
Date: Mon, 5 Jan 2004 12:29:55 +0100
Message-ID: <3ff94ab4$0$127$edfadb0f_at_dread11.news.tele.dk>
"Bob Badour" <bbadour_at_golden.net> skrev i en meddelelse
news:X6ednQoP0Pvbb2qiRVn-tA_at_golden.net...
> "Peter Koch Larsen" <pkl_at_mailme.dk> wrote in message
> news:3ff7ed4a$0$149$edfadb0f_at_dread11.news.tele.dk...
> >
> > "Bob Badour" <bbadour_at_golden.net> skrev i en meddelelse
> > news:mfGdnV-2Nadl2mqiRVn-vA_at_golden.net...
> > > "Adrian Kubala" <adrian_at_sixfingeredman.net> wrote in message
> > > news:slrnbve73f.ta3.adrian_at_sixfingeredman.net...
> > > > Bob Badour <bbadour_at_golden.net> schrieb:
> > > > > As long as the dbms treats values strictly as values at the
logical
> > > > > level, all values are atomic. A dbms would violate atomicity if it
> > > > > exposes internal structure with concepts such as a current
position
> > > > > within the value, for instance.
> > > >
> > > > I don't think it's so clear-cut. What's the difference between a
> > > > function "value -> current position within value" and a function
"date
> > > > -> month"?
> > >
> > > Month is a derivable value from any date value. Since values have no
> > > locations, a current position within a value is an absurdity.
> > >
> > >
> > > > What if cons cells were used for all non-scalar types. Would
> > > > car and cdr "expose internal structure"?
> > >
> > > Since there are no non-scalar types, I have difficulty finding any
> meaning
> > > in your question.
> > >
> > >
> > What about "what is the value of the fourth character in the last name"?
>
> What about it? Are you suggesting strings are non-scalar? What about the
> third bit in the integer?
>
>
What I meant was that whether or not a value is scalar or not is open to discussion. And from that point a view, an integer (everything but a boolean, actually) could be seen as a nonscalar value. It is interesting that some textbooks seem to disallow arrays in relations (I believe i saw that in older versions of "Introduction to database management systems" by Date - sixth edition, probably) and yet allow strings which basically are just array of char.
A more interesting distinction could be between whether values are finite - leaving room for fixedsize strings and limited precision integers/floating point values.
Kind regards
Peter
Received on Mon Jan 05 2004 - 12:29:55 CET