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Re: list builtins done

From: Chris Welty <cawelty@gmail.com>
Date: Wed, 06 May 2009 10:40:06 -0400
Message-ID: <4A01A146.6010908@gmail.com>
To: Sandro Hawke <sandro@w3.org>
CC: public-rif-wg@w3.org

So who will take up the issue of binding patterns for lists in Core?  Axel? Jos?

-Chris

Sandro Hawke wrote:
> I think the DTB section on RIF lists [1] is now ready for review for
> Last Call.  A few notes and questions:
> 
>    * I removed the func:delete function, because 
>           (a) it's not in xpath,
>           (b) it's confusingly similar to func:remove, and
>           (c) it's trivial emulated:  
>                 func:delete(L, I) = func:except(L, func:make-list(I))
> 
>      Some other functions are trivial emulated, but they're in xpath.  I
>      think the bar is higher for us adding functions.  This way, the
>      only ones we're adding are is-list, list-contains, make-list, and
>      get.  list-contains is that only the can be emulated:
>              list-contains(L, I) iff count(index-of(L, I)) > 0 
>      but I think we specifically discussed that and agreed it was
>      worthwhile to have list-contains.
> 
>      Obviously, if someone actually wants it, I'm okay with putting
>      func:delete back in.
> 
>    * This section has examples.  I could trivially suppress them for now
>      (this wiki-text is generated by a program [2]), if they bother
>      people.  I like them.  They have all been checked by my demo code
>      [3].  I'm willing to make similar examples for the rest of DTB for
>      a later edition.
> 
>    * I don't know the right binding pattern for list-contains.  Above, I
>      was assuming it was (b,b), but I can imagine some utility to all
>      binding patterns, and at least (b,u) seems pretty reasonable.  It's
>      not clear to me whether PR systems would do what I'm imagining with
>      that, but it'd be nice to write rules like:
> 
>          forall M (        
>            if   list-contains(eg:list_of_friends, M)
>            then eg:is_friend(M)
>          )
> 
>      Without it, I guess you'd need some much more cumbersome
>      tail-recursive rules like this:
> 
>          friend_list(eg:list_of_friends)     
>          forall L M (
>            if   friend_list(L) and
>                 get(L, 0) = M
>            then eg:is_friend(M)
>          )
>          forall L  (
>            if   friend_list(L) and
>                 count(L) > 0
>            then friend_list(sublist(L, 1))
>          )
> 
>      PR folks, what do you want, there?
> 
> I think that it.  This complete ACTION-760.
>   
>      -- Sandro
> 
> 
> [1] http://www.w3.org/2005/rules/wiki/DTB#Functions_and_Predicates_on_RIF_Lists
> [2] http://dev.w3.org/cvsweb/2009/rif/list_builtins.py
> 
> 

-- 
Dr. Christopher A. Welty                    IBM Watson Research Center
+1.914.784.7055                             19 Skyline Dr.
cawelty@gmail.com                           Hawthorne, NY 10532
http://www.research.ibm.com/people/w/welty
Received on Wednesday, 6 May 2009 14:40:49 GMT

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