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Re: Two issues with RIF-Core

From: Gary Hallmark <gary.hallmark@gmail.com>
Date: Fri, 8 May 2009 13:06:26 -0700
Message-ID: <499257640905081306s35bd9175vbe75f6e69c5c8ca6@mail.gmail.com>
To: Dave Reynolds <der@hplb.hpl.hp.com>
Cc: Sandro Hawke <sandro@w3.org>, RIF WG <public-rif-wg@w3.org>
ok, I can implement quantification over property names using Java
reflection, so how about

Frame ::= TERM '[' ((Const|Var) '->'  TERM)* ']'

On Fri, May 8, 2009 at 9:13 AM, Dave Reynolds <der@hplb.hpl.hp.com> wrote:
> Sandro Hawke wrote:
>>>>
>>>> 2. PRD and Core allow frame properties to be TERMs, i.e. Frame ::=
>>>> TERM '[' (TERM '->' TERM)* ']'
>>>>
>>>> This is likely to be a problem for most production rule engines. It
>>>> would be much easier if Frame ::= TERM '[' (Const'->' TERM)* ']'
>>>
>>> Agreed.
>>
>> I'm not sure this is a good idea.
>>
>> Partly for the sake of argument, let me suggest an alternative.  Take
>> frames out of Core and PRD.  If we restrict frames as you're proposing,
>> then (as far as I can tell) they don't actually provide any
>> functionality.  Wherever you were using s[p->o], just use p(s,o).  Why
>> have two parallel features that provide exactly the same functionality?
>> As I understood it, the whole point of frames was to allow for
>> quantifying over predicates.
>>
>> Dave, with this change, how would you implement RDFS (etc) rules?
>
> Sorry, I was misunderstanding the suggested change and spoke without
> thinking clearly. Must have been still asleep.
>
> I assumed, wrongly, that what Gary was trying to do was to exclude Lists and
> external functions from frame slots, not stop you using vars to quantify
> over slot names.
>
> You are right, forcing frame slots to be only constants would be too strong
> and would invalidate their use in RDF.
>
> I withdraw my "Agreed" and will go get some more caffeine to see if I can
> get my brain working again.
>
> Dave
>
> [Though of course frames are just syntactic sugar for something like
> rif:triple(s,p,o), they don't provide any added expressivity.]
>
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>



-- 
Cheers,

Gary Hallmark
Received on Friday, 8 May 2009 20:07:01 GMT

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