Re: the two questions
Date: Sun, 25 Nov 2007 17:24:16 GMT
"David Cressey" <cressey73_at_verizon.net> wrote in message
> "Brian Selzer" <brian_at_selzer-software.com> wrote in message
>> "JOG" <jog_at_cs.nott.ac.uk> wrote in message
>> > On Nov 24, 12:38 am, vldm10 <vld..._at_yahoo.com> wrote:
>> >> Not long time ago on this NG there were few posts which involved an
>> >> entity with 200+ attributes.
>> >> Let all these attributes satisfy the following two conditions:
>> >> 1) All these attributes are mutually independent
>> > Then there are no functional dependencies so the entity can only be
>> > identified by the collection of all its attributes - and hence you'd
>> > end up with an equivalent superkey. If any of those attributes
>> > "change" it would also therefore be a different entity altogether.
>> It cannot be determined whether two representations from two distinct
>> in time refer to the same individual--even if all of the attribute values
>> are identical--unless, of course, one of the attributes is a surrogate;
> Do you mean "surrogate" or "synthetic" ?
I don't know what you mean by "synthetic." What I mean by a surrogate is a
value that always refers to a particular individual and can never refer to
any other individual. How it comes into being is irrelevant.
Received on Sun Nov 25 2007 - 18:24:16 CET