Re: [BLD] My comments on version dated 5/10

Michael Kifer wrote:
> 
>>- In some examples, we have 2 different serialisation for the same 
>>expression: how do we deal normatively with that? We could define a 
>>normal form for RIF XML rules; or we could require that implementations 
>>preserve the form of an expression, for round-tripping purposes (that 
>>would be kind of difficult, though)
> 
> Can you point to these specifically?

Strictly speaking, the only one is example 3 [1] in section 3.1.1.2, 
which offers 2 translations of the same rule:
1. (x, y, z, u), Head(x) :- Body1(x, y, z, u);
2. (x) Head(x) :- Body2(x)
where body2 contains exsitentially quantified formulae.

[1] Btw, it should be number 5, and the next one number 6, instead of 4, 
if I am counting examples correctly

> We need to fix that.

Well, we need to fix the inconsistency between that example and the 
sentence that says: "the free variables in a CONDITION formula are 
_precisely_ those that also occur in the then part of the rule" (section 
2.11.2, last par. before example 1).

But "fixing" the more general issue of whether RIF allows several 
equivalent forms for the same statement is a different question: if we 
want any specific rule to have one and only one expression in RIF, then 
we need to specify a RIF normal form; but that would impact the 
round-tripping issue, not mentionning complexity and efficiency of 
implementation; or the added work that would require (to specify such a 
normal form). On the other hand...

So, no quick fix to that, I fear (but fix the inconsistency for WD2 one 
way or another, of course: my preference would be to change _precisely_ 
for _at_least_ in the above sentence, because it leaves more doors open; 
but I would not kill anybody for that).

>>- sect. 2.1.1.2, 5th par. ("We now give an EBNF...), but-last sentence, 
>>"It is not intended to be used as a concrete syntax for a rule 
>>language": add "RIF concrete syntax is the XML syntax for interchange"?
> 
> Here we are talking about  a concrete language for a rule language, not
> about a RIF concrete language.

I understand that. My suggestion was to add a sentence that explains why 
(we are not specifying a concrete syntax for a rule language) by 
refocusing the reader on the purpose of RIF (after you've read all that 
stuff about well-formed formulas, signatures, data types etc, it might 
be a good idea to refresh one's mind about what it is all about :-)

Christian

Received on Wednesday, 10 October 2007 11:46:11 UTC