Re: [BLACKBOX] EBNF question

From: [at]} <Bob>
Date: Thu, 16 Feb 2012 07:47:07 -0000

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[...]
>
> You want to make a list of tokens necessary without defining their
> positions.
> You'll have to either invent a syntax for that, or check for the
> presence of
> all the necessary tokens elsewhere, for that is not a syntax, but
> rather a
> semantic check. It does not set the rules for relative positions of
> tokens
> (which is syntax), it sets rules for the contents of a file (which is
> semantics).

Thanks Alexander. In fact, my understanding is that this is syntax, although
it seems to be impossible to do in EBNF and related notations.

It is straightforward in the Barker crowsfoot notation for database schemas
- just use the symbol for 1..M - but relational databases are inherently
unordered.

Perhaps the difficulty is that I am trying to apply a rule to sequential
data structures that is incompatible with the notion of ordering, but it
seems to me that EBNF etc. ought to be able to specify this.

B

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Received on Thu Feb 16 2012 - 08:47:07 UTC