Re: Domain

"Peter Koch Larsen" <pkl_at_mailme.dk> wrote in message news: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.

Since all values in an actual dbms are finite, I do not find this a useful distinction either. Received on Mon Jan 05 2004 - 21:44:32 CET