Re: Issue-12 and the next UCR draft

Bijan Parsia wrote:
> 
> [snip]
>>> There are already a large number of in-use or proposed semantic web 
>>> rule languages (CWM, Euler,
> 
> These are not rule languages, but rule engines. The language they 
> support is N3.

They certainly both use the N3 syntax for rules, I wasn't sure if they 
supported the same range of operators and builtins these days and so 
whether they are really equivalent implementations of a single language. 
Jos?

>>> By phrasing this goal as "provide the basis for ..." we are 
>>> indicating that there is unlikely be a single semantic web rule 
>>> language and that RIF will not propose one. However, it also says 
>>> that RIF should go further than minimal compatibility and try to 
>>> bring some order to the chaos of semantic web rule languages.
> 
> Good luck :)

Let me be clear on this. I'm not saying "the working group must do this" 
I'm saying "the working must say clearly whether it is doing this or not".

Personally, about 2 hours into the first f2f meeting I suspected the 
answer was probably going to end up as "no, we're not". I just want 
clarity, partly for expectation setting, and partly (being parochial 
here) because it will affect how HP regards my time being spent in RIF.

> There are deep issues with BNodes that have hurt us in SPARQL, and I 
> think most extant SemWeb rule languages largely punt on them. It would 
> be good to deal with them properly. (e.g., are BNodes scoped to the 
> document? Even when they appear in rules?)

Agreed there are dragons there.

[quote from separate msg]
> Sandro, the problem is that most extant rule languages do *not* treat BNodes as existentials, but skolemize them in a variety of ways. There are subtle and tricky issues esp. when talking with people with different views of how they work. Then, once you have agreement there, how they integrate with logic programming type rules is, again, very tricky. It's a research topic on its own and many of the extant rule languages have not attended to them (which is fine, except for poor standards bodies that have to harmonize with existing specifications).  

Definitely an issue, there are places where the skolemize approach 
appears to be more pragmatically useful - even though unclean.

Of course by saying "basis for ..." we are giving ourselves scope to not 
answer those questions. We could punt entirely on bNodes, we could give 
partial treatments (no bNodes in heads) or whatever.

Or we could decide that it is too hard or too early to do anything along 
these lines and we say so clearly in the UCR rather than ask for 
comments on the issue.

Dave

Received on Wednesday, 13 September 2006 17:18:52 UTC