Re: No exceptions?

J M Davitt wrote:
paul c wrote:
Bob Badour wrote:
...

The way to avoid exceptions is to treat them as compile-time errors.


I take it you really mean "ONE way to avoid exceptions ...". For one thing, I am interested in being able to express "x join y" in advance of defining a header for "x" (and I would like to evaluate it as well if that is logically possible!).

p

This has me scratching my head. Without a heading, there can be no
parameters. Without parameters, there can be no arguments. Without
arguments, there can be no quantifiable proposition. Which leads me
to, "A relation without a predicate is... What?" I find this
especially curious because you mention the Closed World Assumption
in the same post. (Don't forget the Excluded Middle!)

So, Paul, what are you trying to explore?


Maybe instead of saying "defining a header", I should have said "in advance of entering a header". I had in mind that an "empty" header would be assumed.

My peculiar view doesn't require me to ask "what is the predicate of such and such a relation". This will sound ridiculous to most people I think because one would ask "well, what good is a database whose predicates we don't know?". OTOH, one aspect that for me defines a relational engine is precisely that it must not circumscribe even in the most indirect of ways what predicate a particular relation has, its whole value is in being to manipulate relations without knowing that - otherwise it would be an application!

Apologies if this is metaphysical mumbo-jumbo. Will ponder the CWA and excluded middle again.

p
.

Relevant Pages

  • Re: header part of the value?
    ... as a <header, body> tuple. ... *Why* is the predicate not itself a constraint? ... Do we *have* to have a predicate? ... before and after you insert a row for a new employee. ...
    (comp.databases.theory)
  • Re: header part of the value?
    ... as a <header, body> tuple. ... *Why* is the predicate not itself a constraint? ... Do we *have* to have a predicate? ... a relvar is a name bound to a relation value. ...
    (comp.databases.theory)
  • Re: No exceptions?
    ... I am interested in being able to express "x join y" in advance of defining a header for "x". ... So, Paul, what are you trying to explore? ... OTOH, one aspect that for me defines a relational engine is precisely that it must not circumscribe even in the most indirect of ways what predicate a particular relation has, its whole value is in being to manipulate relations without knowing that - otherwise it would be an application! ... with the confidence that your expressions are still correct. ...
    (comp.databases.theory)
  • Re: predicate, constraints, header, relvar, and relation
    ... Does a predicate apply to a relvar or a relation? ... While the concept of constraint it meaningless for values, every constraint basically describes some property of consistent values. ... because a relation literal must have a header. ...
    (comp.databases.theory)
  • Re: Question about proof by contradiction
    ... definition must be in the form of a predicate. ... You MAY be using the excluded middle, ... of these statements are theorems violates something that I'd *like* to ... which is the law of the excluded middle. ...
    (sci.math)