Re: The naive test for equality

"Paul" <paul_at_test.com> wrote in message news:42f50fc1$0$24006$ed2619ec_at_ptn-nntp-reader01.plus.net...
> Marshall Spight wrote:
> >>I've kind of lost track of what started this thread in the first place
> >>now! I think it was just to say I didn't think there was any real
> >>difference between equality and equivalence relations. Each one defines
> >>the other.
> >

OK, let me jump in with what I think I was about with this thread in the first place.

A lot of other discussion hinges about the interaction between the relational engine and the type engine.

I think there are multiple layers of representation/interpretation in any system of representing meaning using symbols.

For certain equalities of the underlying things ("values" for some people), it's the type engine that knows when two tokens are representations for the same underlying thing. Thus, if we want to know whether 1/2 s really equal to 2/4 or not, we consult the appropriate tpye engine, in this case the rational type engine. If we want to know whether 123.45E1 is really equal to 12.345E2 we consult the floating point number type engine.

As far as I'm concerned "consulting the type engine" is another way of saying what VC said when he said we must put the items in context before we can test them for equality.

With regard to whether A is equal to B or not, we need to consult three engines:

First the variable typing engine to see if A and B are or are not of the same type. If we have static typing of variables, we can do this test at compile time.

Next, the variable state remembering engine to retrieve the current (in context) value of A and B.

Next the type engine determined by the common type of A and B to find out whether the values are really the same or not.

If we omit the last step, we will end up doing a naive test for equality. If there are any synonyms that the type engine knows about and we don't know about, then our test for equality will be naive.

Here's where I'm going with this: in an SQL DBMS, where is the type engine for the type "SQL Table". Or isn't there one? Received on Sat Aug 06 2005 - 23:30:50 CEST