$shapesGraph (was: Quick Comments on https://www.w3.org/TR/2016/WD-shacl-20160814/)

On 23/09/2016 11:36, Peter F. Patel-Schneider wrote:
>
>> $shapesGraph
>>
>> The status of $shapesGraph is unclear: "SPARQL variables using the $
> marker represent external values that must be pre-bound or substituted in
> the SPARQL query before execution." "SHACL validation engines MAY pre-bind
> the variable $shapesGraph to provide access to the shapes graph."
>>      Comment (HK): The MAY is clarified in the following sentence (Access
> to the shapes graph is not a requirement etc). I believe it would be
> confusing to soften up the must in the first sentence because of this
> exception.
>
> It remains that there are two controlling wordings for how to handle
> $shapesGraph, one with a must (which probably should be MUST) and one with
> MAY.  These appear to be contradictory.

The current wording of this has evolved to:

Can be used to query the shapes graph as in|GRAPH $shapesGraph { ... }|. 
If the shapes graph is a named graph in the same dataset as the data 
graph then it is the IRI of the shapes graph in the dataset. Not all 
SHACL Full processors need to support this variable. Processors that do 
not support|$shapesGraph|/must/report afailure <#dfn-failure>if they 
encounter a query that references this variable. Use of|GRAPH 
$shapesGraph { ... }|should be handled with extreme caution. It may 
result in constraints that are not interoperable across different SHACL 
Full processors and that may not run on remote RDF datasets.

I can no longer find the original statements and I hope the issue has 
been addressed by the rewrite above.

Holger