Re: comments on current version BLD document: symbols, datatypes, semantics

OK.  So, the only remaining open issue is the question whether the set
of support for datatypes is fixed or not, which is discussed in the
thread following [1].

[1] http://lists.w3.org/Archives/Public/public-rif-wg/2007Oct/0063.html


Just one more remark:

>>> The standard way is to first define an alphabet (which includes all the
>>> symbols, connectives, etc.) and then define the rules for putting the
>>> alphabet symbols together into formulas.  This is not explicitly mentioned
>>> -- an omission. It is mentioned now. In fact, there was a bad typo, which
>>> said "The language of RIF ..." while it should have been "The alphabet of
>>> RIF ...".
>> As I understand, the standard way is to let the alphabet vary; the user
>> can choose an alphabet, and the logic defines which formulas can be
>> obtained from this alphabet and the logical connectives (i.e. the
>> language). in my example above, the alphabet A is chosen by the user,
>> and LA is the language obtained from A and the logical connectives and
>> syntax formation rules in logic.
> 
> Nope. When you define a logic, you would normally say that you have a set
> Const, Var, etc., without giving out many details.
> 
> But when you are specifying a ***concrete language*** then you must state
> what your alphabet is, and it is fixed. An analogy is to say that Java
> should not have a fixed alphabet and each user should be able to decide
> which sequences of characters are to be allowed as variables, integers, etc.
> 
> We are defining a concrete language, not just a logic.

I would argue that the RDF and OWL are concrete languages.  In both
languages, the alphabet is not fixed; the symbols simply have to be of a
specific shape (e.g. URI or literal).
However, as I said, I gave up my resistance to fixing the alphabet :-)

best, Jos

-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
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