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Re: DTB: Problem/Erratum for DTBin function string-join

From: Axel Polleres <axel.polleres@deri.org>
Date: Mon, 17 Aug 2009 23:34:36 +0100
Message-ID: <4A89DAFC.7000502@deri.org>
To: kifer@cs.sunysb.edu
CC: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
Michael Kifer wrote:
> i think using lists is a cleaner solution in general

flagged this with an edNote.


> On Mon, 17 Aug 2009 21:28:27 +0100
> Axel Polleres <axel.polleres@deri.org> wrote:
> 
>  > Hi all,
>  >
>  > While working on the all-builtins use case, I realize a slight
>  > error/problem in DTB now with the function:
>  >
>  > func:string-join(...)
>  >
>  > its xpath/xquery counterpart fn:string-join(...)
>  >
>  > takes two arguments:
>  > - a sequence of strings
>  > - a "separator" string
>  >
>  > now I realize - since this function was introduced when we didn't heva
>  > lists in RIF yet, that we seem to have expected a "flattened" list as
>  > input, i.e. we give the schemas
>  >
>  > ( ?arg1 ?arg2; func:string-join(?arg1 ?arg2 ) )
>  >
>  > ( ?arg1 ?arg2 ?arg3; func:string-join(?arg1 ?arg2 ?arg3 ) )
>  >
>  > ...
>  >
>  > ( ?arg1  ?arg2 ... ?argn; func:string-join(?arg1 ?arg2 ... ?argn ) )
>  >
>  >
>  > Anyways, the semantics is defined in terms of fn:string-join, which
>  > didn't work so far, but only works with a small fix, i.e. interpreting
>  > the first n-1 arguments as the sequence argument of the CPAth/Xquery
>  > fn:string-join function. "Historically" this is IMO what we meant, as
>  > there was no lists.
>  >
>  > Thus, I see two options for fixing this:
>  >
>  > a) stick with the flattened version, interpreting the first n-1
>  > arguments as the sequence argument of the CPAth/Xquery fn:string-join
>  > function and the last argument as the separator string.
>  >
>  > b) make the function with a fixed arity of 2,  the domain of the first
>  > argument being a list of strings and the second argument the separator
>  > string.
>  >
>  > I implemented option a) now, since it is the "least intrusive" change to
>  > the current doc, see
>  >
>  > 
> http://www.w3.org/2005/rules/wiki/index.php?title=DTB&diff=10665&oldid=10495 
> <http://www.w3.org/2005/rules/wiki/index.php?title=DTB&diff=10665&oldid=10495>
>  >
>  > however, b) seems somehow the more natural way to proceed. The
>  > disadvantage/worry I see with b) is that we might want to implement
>  > "emulating" sequences by lists as input in other functions as well...
>  > Opinions?
>  >
>  > Axel
>  >
>  >
>  >
> 


-- 
Dr. Axel Polleres
Digital Enterprise Research Institute, National University of Ireland, 
Galway
email: axel.polleres@deri.org  url: http://www.polleres.net/
Received on Monday, 17 August 2009 22:35:23 GMT

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