Re: The naive test for equality

David Cressey wrote:
> "Marshall Spight" <marshall.spight_at_gmail.com> wrote in message
> news:1123516890.932363.109840_at_f14g2000cwb.googlegroups.com...
>
> > > So the process of normalizing is choosing one, out of an equivalence
> class,
> > > according to some criterion, and using the symbol that represents the
> > > chosen element to act as the normalized form for the entire class.
> >
>
> > I don't see how this is a particularly useful way to look at
> > the issue. It doesn't separate the idea of the lexical symbols
> > we use to display and enter values, and the abstract values
> > themselves.
> >
>
> The word "symbols" refers not only to the symbols used to exchange data
> between people and computers, but also to each of the data items inside the
> computer.

So now we have, in addition to 'representation', a new word 'symbol'.  What is even worse, in your vocabulary, it means two different things.  Nice..

>In other words, what the computer stores is all symbolic, right
> down to the most atomic symbols, zero and one.

This is not true. What the computer uses to store numbers (and characters) is called bits, not symbols. Besides, the way the computer implements numbers and characters is entirely irrelevant at the logical level.

>
> When various "engines" (or "objects" if you prefer) inside a large system
> exchange data with each other (or "messages" if you prefer), they use
> symbols to communicate with each other.

This phrase is so ambiguous as to be almost devoid of meaning. What are "engines" and how do they "exchange data" ? What precisely do you mean ?
Hardware components ? Abstract stuctures communicating using some protocol ? Or something else ?

>
>
>...
> But the number "5/10" could be generated
> at run time as well. If such an expression is evaluated at run time, it
> will evaluate to "1/2" (or some bit pattern that is used to represent that
> number).
>

Whatever bit pattern is used to implement a number is irrelevant at the logical model level.

>
> I started this discussion, about the naive test for equality, based on the
> supposition that if you just compared two representations of a value, you
> could tell whether they are the same or not. The synonym and homonym
> problems are two classic problems that arise whenever you do that. They
> were referred to as "synonym problem" and "homonym problem", in the
> literature of about 30 years ago. I'm sorry, but my memory fails me when it
> comes to citing sources for this.
>
> The two words, "synonym" and "homonym" are borrowed from the argot of
> natural linguistics, but the two problems arise whenever data is
> represented.

In modelling, "synonym/homonym problems" are problems only when they are self-induced.

>
>
> >
> > Marshall
> >
Received on Tue Aug 09 2005 - 22:30:09 CEST