Re: Is a function a relation?
Date: Tue, 30 Jun 2009 02:15:32 GMT
On Sat, 27 Jun 2009 12:55:16 +1000, David BL <davidbl_at_iinet.net.au> wrote:
> On Jun 27, 10:10 am, "Joe Thurbon" <use..._at_thurbon.com> wrote:
>> What are you talking about when you say interpretation?
> I completely agree that an interpretation in model theory is a
> mathematical construct. I don't believe Brian was using the word
> interpretation in that sense, because he spoke about a UoD that can
> exist in time and space. His words:
> "... if what is in the Universe of Discourse can
> exist in time and space, then database values can
> exist in time and space. A value is the result of
> applying for a given term the valuation function
> which maps terms expressed in a formal language to
> things in the Universe of Discourse under an
> I assumed he was talking about the idea to interpret mathematical
> relations as predicates that apply to the real world. i.e. external
Sorry about the delay in replying, this conversation seems to have moved on. But thanks for clarifying.
> As C.Date says:
> "... while internal predicates are a formal
> construct, external predicates are an informal
> construct merely. Internal predicates are (loosely)
> what the data means to the DBMS; external
> predicates, by contrast, are what the data means
> to the user."
> An external predicate, being informal, is typically stated in natural
Out of interest, Date also states his formal predicates in natural language, at least in Logic and Databases.
Joe Received on Tue Jun 30 2009 - 04:15:32 CEST