Re: The MySQL/PHP pair

Dawn M. Wolthuis wrote:
> I know I have some reading to do re 2nd order logic so that I really
> understand just where we move from 1st to 2nd order logic being required and
> just where 2nd order logic is problematic when querying data.
>
> What is the problem if I want to persist the proposition:
>
> Person
> Bob Smith has e-mail addresses of bob_at_aol.com and bobsmith_at_msn.com

Well, want you really want to do (or at least what the relational model does) is collect together all propositions that fit the same "template" and store them together.

If you do this as:

  Person P has email addresses of E1 and E2

then you are restricted to two email addresses per person. What you are really saying you want to do is collect together:

  Bob Smith has e-mail addresses of bob_at_aol.com and bobsmith_at_msn.com   Jane Doe has an e-mail address of jdoe_at_aol.com   Bill Bloggs has e-mail addresses of bill_at_yahoo.com, bill_at_hotmail.com    and bill_at_aol.com

But the predicate for this would be something like:

  Person P has email addresses of E1, E2, E3, ...

and it's this unknown number of parameters that is the problem - a first order predicate has to have a fixed number of parameters.

Paul. Received on Fri Nov 05 2004 - 20:09:04 CET