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Re: Grammar presentation syntax FLD and BLD

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Sat, 01 Mar 2008 15:19:10 +0100
Message-ID: <47C965DE.7020409@inf.unibz.it>
To: Michael Kifer <kifer@cs.sunysb.edu>
CC: RIF <public-rif-wg@w3.org>
I updated the grammars according to the e-mail discussion.

There are three places where sequences of Unicode characters are used, 
namely as names of arguments of functions and predicates, as constant 
identifiers, and as names of variables.  I used the same name LITERAL in 
all three places.
To accommodate the fact that FLD allows implication in conditions, I 
added the implication to the CONDITION production.
For uniformity with BLD I kept the RULECONTENT production; however, if 
such uniformity is not required, the production may be removed and the 
rules and simply be a CONDITION.

FLD Grammar:

  Ruleset         ::= 'Ruleset( ' absolute-IRI? Metadata* Rule* ' ) '
  Rule            ::= 'Rule( ' absolute-IRI? Metadata* RULECONTENT ' ) '
  RULECONTENT     ::= 'Forall' Var+ '(' CONDITION (':-' CONDITION)? ')' 
| CONDITION (':-' CONDITION)?

   UNITERM        ::= TERM '(' (TERM* | (LITERAL '->' TERM)*) ')'

   CONDITION      ::= 'And' '(' CONDITION* ')' |
                      'Or' '(' CONDITION* ')' |
		     CONDITION ':-' CONDITION |
                      'Exists' Var+ '(' CONDITION ')' |
                      'Forall' Var+ '(' CONDITION ')' |
                      'Neg' CONDITION |
                      'Naf' CONDITION |
                      ATOMIC
   ATOMIC         ::= Predicate | Equal | Member | Subclass | Frame
   Predicate      ::= UNITERM | 'Builtin ( ' UNITERM ' ) '
   Equal          ::= TERM '=' TERM
   Member         ::= TERM '#' TERM
   Subclass       ::= TERM '##' TERM
   Frame          ::= TERM '[' (TERM '->' TERM)* ']'

   TERM           ::= Const | Var | Function| Equal | Member | Subclass 
| Frame
   Const          ::= '"' LITERAL '"^^' SYMSPACE
   Var            ::= '?' LITERAL
   Function       ::= UNITERM | 'Builtin ( ' UNITERM ' ) '

   Metadata       ::= ' Metadata ( ' METADATALIST ' ) '
   METADATALIST   ::= absolute-IRI MetadataValue | METADATALIST ' ; ' 
METADATALIST
   METADATAVALUE  ::= Const | ' [] ' | ' [ ' METADATALIST ' ] '


   SYMSPACE       ::= absolute-IRI




BLD grammar:

  Ruleset         ::= 'Ruleset( ' absolute-IRI? Metadata* Rule* ' ) '
  Rule            ::= 'Rule( ' absolute-IRI? Metadata* RULECONTENT ' ) '
  RULECONTENT     ::= 'Forall' Var+ '(' ATOMIC (':-' CONDITION)? ')' | 
ATOMIC (':-' CONDITION)?

   UNITERM        ::= Const '(' (TERM* | (LITERAL '->' TERM)*) ')'

   CONDITION      ::= 'And' '(' CONDITION* ')' |
                      'Or' '(' CONDITION* ')' |
                      'Exists' Var+ '(' CONDITION ')' |
                      ATOMIC
   ATOMIC         ::= Predicate | Equal | Member | Subclass | Frame
   Predicate      ::= UNITERM | 'Builtin ( ' UNITERM ' ) '
   Equal          ::= TERM '=' TERM
   Member         ::= TERM '#' TERM
   Subclass       ::= TERM '##' TERM
   Frame          ::= TERM '[' (TERM '->' TERM)* ']'

   TERM           ::= Const | Var | Function
   Const          ::= '"' LITERAL '"^^' SYMSPACE
   Var            ::= '?' LITERAL
   Function       ::= UNITERM | 'Builtin ( ' UNITERM ' ) '

   Metadata       ::= ' Metadata ( ' METADATALIST ' ) '
   METADATALIST   ::= absolute-IRI METADATAVALUE | METADATALIST ' ; ' 
METADATALIST
   METADATAVALUE  ::= Const | ' [] ' | ' [ ' METADATALIST ' ] '


   SYMSPACE       ::= absolute-IRI


Best, Jos

Michael Kifer wrote:
> Jos wrote:
>>>> Incidentally, I think there is a problem with the syntax for rules, as 
>>>> specified in FLD.  Namely, a rule is an implication phi :- psi; no 
>>>> quantification seems to be allowed. In the grammar below I also allowed 
>>>> rules with universal quantification.
>>> There are also quantified formulas. In FLD you can have arbitrary quantifiers.
>>> I could have called phi :- psi a "Rule Implication" instead, but "Rule"
>>> seemed shorter and acceptable.
>> I guess this means an FLD rule set is a set of formulas?
> 
> Yes, because FLD is supposed to cover a possible future FOL dialect,
> disjunctive LP, and Lloyd-Topor extensions.
> 
>>> Note that the formal syntax uses "universal" for what BNF calls a "rule".
>>> These universals correspond to "Implies" in BNF. Unfortunately, Implies is
>>> not so good, if FLD is taken into the account, since FLD can have two kinds
>>> of "implies": :- and <-. Currently, <- is not used in FLD, but it could be,
>>> so it is better to avoid the confusion.
>> Actually, I was proposing to get rid of "Implies" in BNF, because I was 
>> not convinced of its usefulness.
>>
>> Could you actually point me out where the implication <- is defined in 
>> FLD?  I could not find it.
> 
> I said that currently FLD *does not* use the classical implication
> connective (->), but we might include it in the future (for instance, for
> FOL and languages that support Lloyd-Topor extensions). For this reasons, I
> avoided calling phi :- psi an "Implication" in the formal syntax of FLD
> (not to be confused with the BNF of BLD, which used Implies).
> 
> So, ideally, to be compatible with FLD and to be extensible, it may be
> necessary to call the top level nonterminals in BNF "Formula" or "FormulaSet".
> I realize that for BLD the names "Rule" and "RuleSet" seem more
> appropriate, but if we think about extensible BNF grammars then we might
> need to be more general.
> 
> 
> 	regards
> 	  --michael  
> 
>> Best, Jos
>>
>>> Proposals for better names would be appreciated.
>>>
>>>
>>> 	--michael  
>> -- 
>>                           debruijn@inf.unibz.it
>>
>> Jos de Bruijn,        http://www.debruijn.net/
>> ----------------------------------------------
>> One man that has a mind and knows it can
>> always beat ten men who haven't and don't.
>>    -- George Bernard Shaw
>>
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>> --------------ms050207030102090906040705--
>>
> 
> 

-- 
                          debruijn@inf.unibz.it

Jos de Bruijn,        http://www.debruijn.net/
----------------------------------------------
One man that has a mind and knows it can
always beat ten men who haven't and don't.
   -- George Bernard Shaw


Received on Saturday, 1 March 2008 14:19:24 GMT

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