Re: caution on using EXISTS and pre-binding in SHACL

At least sh:class, sh:classIn, sh:equals, and sh:in hit a case where the
specification of EXISTS does the wrong thing for SHACL.

See also
https://lists.w3.org/Archives/Public/public-data-shapes-wg/2016Jun/0123.html

peter


On 06/19/2016 02:05 PM, Peter F. Patel-Schneider wrote:
> I spent some time last week turning over rocks in the SPARQL specification
> to see what's underneath them.  I found a lot of ugly stuff there,
> particularly related to EXISTS.  It is even the case that different SPARQL
> impleentations diverge on the behaviour of EXISTS.
> 
> This matters to SHACL in two ways.  First, EXISTS is used in the definitions
> of many SHACL core constraint components.  I don't know if any of these uses
> of EXISTS hit any problems, but I don't think that I have found all the
> problems with EXISTS.  Even if the core constraint components don't hit any
> problems, EXISTS is going to be important for extension constraint
> components and these could easily hit problems with EXISTS.  Second, SHACL
> pre-binding is defined in a way very similar to the way that EXISTS is
> defined so it is entirely possible that the definition of pre-binding has
> problems.  Pre-binding is central to the definition of SHACL and central
> to the extension mechanism in SHACL so its definition is going to have be
> examined extremely closely.
> 
> This all is in addition to the problems in the definition of pre-binding
> that I have already pointed out.
> 
> 
> Peter F. Patel-Schneider
> Nuance Communications
>

Received on Wednesday, 22 June 2016 21:53:15 UTC