Re: What is analysis?
From: paul c <toledobythesea_at_ooyah.ac>
Date: Thu, 06 Dec 2007 15:53:47 GMT
Message-ID: <fWU5j.2544$iU.1774_at_pd7urf2no>
>> Bob Badour answered this; I'll just add a quote from Date's Introduction
>> to Database Systems (2004):
>>
>> In his [1970] paper, Codd uses the term /time-varying relations/ in
>> place of our preferred /relation variables/ (relvars). But /time-varying
>> relations/ is not really a very good term. First, relations as such are
>> /values/ and simply do not "vary with time" (there is no notion in
>> mathematics of a relation having different values at different times).
>> Second, if we say in some programming language, for example, DECLARE N
>> INTEGER ; we do not call N a "time-varying integer", we call it an
>> /integer variable/.
>>
>> (End quote)
Date: Thu, 06 Dec 2007 15:53:47 GMT
Message-ID: <fWU5j.2544$iU.1774_at_pd7urf2no>
David Cressey wrote:
> "Jon Heggland" <jon.heggland_at_ntnu.no> wrote in message > news:fj641f$m36$1_at_orkan.itea.ntnu.no... >
>> Bob Badour answered this; I'll just add a quote from Date's Introduction
>> to Database Systems (2004):
>>
>> In his [1970] paper, Codd uses the term /time-varying relations/ in
>> place of our preferred /relation variables/ (relvars). But /time-varying
>> relations/ is not really a very good term. First, relations as such are
>> /values/ and simply do not "vary with time" (there is no notion in
>> mathematics of a relation having different values at different times).
>> Second, if we say in some programming language, for example, DECLARE N
>> INTEGER ; we do not call N a "time-varying integer", we call it an
>> /integer variable/.
>>
>> (End quote)
> > Thanks for the above I'm going to try to incorporate "relvar" into my > vocabulary, at the expense of misusing it several times in public. Be > forgiving, while correcting me. > ...
Date gives a rationale for the term at:
http://www.dcs.warwick.ac.uk/~hugh/TTM/relvars.pdf Received on Thu Dec 06 2007 - 16:53:47 CET