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Re: ACTION -393 completet

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Mon, 10 Dec 2007 16:01:01 +0100
Message-ID: <475D54AD.9040202@inf.unibz.it>
To: axel@platon.escet.urjc.es
CC: public-rif-wg@w3.org


axel@platon.escet.urjc.es wrote:
>>> a summary of options I added in the end of the built-ins wiki page:
>>>
>>>  http://www.w3.org/2005/rules/wg/wiki/List_of_BLD_built-ins
>>>
>>> Please check the new Section
>>> "Syntactic Representation of built-ins in RIF"
>>> on that page.
>>>
>>> 3 options are discussed and pros and cons listed, examples in
>>> representation syntax and XML syntax given, as far as possible:
>>>
>>>  a. No special representation: IRIs are sufficient to identify built-ins
>> The proposal mentioned on the page of not allowing the use of IRIs for
>> the representation of logical functions seems to me an absolute choose
>> one.  We are creating a language for exchange *over the Web*; so, the
>> use of IRIs will presumably be a lot more prevalent than the use of
>> local symbols.  In fact, a lot of people (including me) have indicated
>> that they do not need local symbols at all.
>>
>> Furthermore, we might want to allow people to use built-ins which are
>> not defined by RIF, without requiring them to specify another RIF dialect.
>> If we decide to allow that, then it is clearly necessary to distinguish
>> built-in predicates from other predicates, to indicate that people
>> really need to understand the built in before they can evaluate it.
>>
>> In general, adopting this option would violate the following resolution
>> of F2F8:
>> "RESOLVED: no invisible extensions (official or user extensions)"
>>
>>>  b. Modules
>> I would argue against this option for three reasons:
>> - it puts an additional burden on the user; he has to specify a module
>> whenever he wants to specify a built-in
>> - I expect that putting modules on the critical path for phase 1 will
>> introduce a significantly delay
>> - I see no benefit in the use of modules for built-ins; it merely seems
>> to impede the flexibility
>>
>>>  c. Special syntax to distinguish evaluated predicates from logical
>>> predicates
>> I did not really understand the proposal.  There is a production for
>> ExtTerm, but it is not clear how this fits in the overall syntax. I
>> assume that the atomic and term productions are meant to be changed as
>> follows:
>>
>> ATOMIC      ::= Uniterm | Equal | ExtTerm
>> TERM        ::= Const | Var | Uniterm | ExtTerm
> 
> yes, the latter only if we allow also built-in/evaluated *functions* and
> not only predicates.
> 
>> This seems to me the most elegant and flexible solution, which puts the
>> least burden on the user.
>>
>> One small comment: I do not find the "&"-prefix solution very elegant.
>> It suggests that "&" is a part of the name,
> 
> this was meant purely to make them syntactically distinguishable. & is not
> allowed in names. if local constants allow only ncnames (which I assumed)
> any other special symbol would also be fine for me.
> 
> 
>> or a modifier of the name,
>> where as it is meant as a modifier of the complete term. I would rather
>> propose:
>>
>> ExtTerm ::= ' BuiltIn( ' Uniterm ' ) '
> 
> How is that distinguishable from a local function term?

A local function term looks like: localConst^^rif:local(...)

A built-in (in my proposal) looks like: BuiltIn(myConst^^mySymbolSpace(...))

To meet they look quite distinct.

> If it would work, 
> 'Eval' would equally make more sense to me (... isn't something like Eval
> used in Lisp? Sorry to have to ask, I only remember vaguely...)

I don't really mind about the keyword itself.  However, "Eval" seems to
apply only to functions, and not other kinds of built-in operators (such
as comparison).

Best, Jos

> 
> 
>> so that it is clear that the modifier applies to the complete term.
>>
>> Best, Jos
>>
>>> comments welcome,
>>> Axel
>>>
>> --
>> Jos de Bruijn            debruijn@inf.unibz.it
>> +390471016224         http://www.debruijn.net/
>> ----------------------------------------------
>> If you live to be one hundred, you've got it
>> made. Very few people die past that age.
>>   - George Burns
>>
> 
> 

-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
----------------------------------------------
If you live to be one hundred, you've got it
made. Very few people die past that age.
  - George Burns


Received on Monday, 10 December 2007 15:01:17 GMT

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