W3C home > Mailing lists > Public > public-rdf-shapes@w3.org > February 2017

Re: limiting ill-formed nodes in SHACL

From: Holger Knublauch <holger@topquadrant.com>
Date: Mon, 27 Feb 2017 16:53:49 +1000
To: public-rdf-shapes@w3.org
Message-ID: <e76bb665-b0fd-ac8d-1bf3-73d10e165ab2@topquadrant.com>


On 27/02/2017 6:17, Peter F. Patel-Schneider wrote:
> It appears that SHACL defines ill-formed nodes too broadly.
>
> Currently the graph
>
> ex:s1 rdf:type sh:NodeShape ;
>   sh:targetClass ex:C1 ;
>   sh:class ex:C2 .
>
> ex:s2 sh:class 5 .
>
> appears to contain an ill-formed node because an object of a triple with
> property sh:class is not an IRI.  Validation results when using this graph
> thus appear to be undefined.
>
> It would be better to limit these requirements to situations where the
> subject of the triple is a shape.

This comment appears to be very similar to your comment 18), see

     https://www.w3.org/2014/data-shapes/wiki/ISSUE-234

>
> Currently the graph
>
> ex:s1 rdf:type sh:NodeShape ;
>   sh:targetClass ex:C1 ;
>   sh:pattern "(" .
>
> contains an ill-formed node because the value of ex:s1 for sh:pattern is not
> a valid pattern argument for the SPARQL REGEX function.  Validation results
> when using this graph are thus undefined.
>
> It would be better to just require that the values of shapes for sh:pattern
> be strings and handle the possible errors produced like SPARQL errors are
> handled elsewhere in SHACL.

This comment appears to be very similar to your comment 45), see

     https://www.w3.org/2014/data-shapes/wiki/ISSUE-234

>
>
> Currently the graph
>
> ex:s1 rdf:type sh:NodeShape ;
>   sh:targetClass ex:C1 ;
>   sh:class ex:C2 .
>
> ex:s2 sh:node ex:s3 .
>
> ex:s3 sh:path ex:p1 .
>
> contains an ill-formed node because ex:s3 is a node shape and it has a value
> for sh:path.  Validation results when using this graph are thus undefined.
>
> It would be better if objects of triples with properties like sh:node only
> made their objects shapes if the subject of the triple was already a shape.
> A suitable inductive definition of shapes that does the right thing is easy
> to produce.

Can you suggest the exact incremental wording to the current definition 
of "shapes" that would cover this scenario? We can then discuss this in 
the WG.

In my personal opinion, at the current state of the process (with only 4 
weeks before CR) I am very hesitant towards changes in the "nice to 
have" category, esp if they may cause follow-up issues or longish email 
discussions. With your own W3C experience I assume you are aware of 
these process limitations, regardless of how much longer we could in 
theory continue with these design questions.

Thanks,
Holger


>
>
> Limiting ill-formed nodes expands the number of graphs that have defined
> behaviour in SHACL without appreciably increasing the complexity of the
> language.
>
>
> Peter F. Patel-Schneider
> Nuance Communications
>
Received on Monday, 27 February 2017 07:22:31 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 17:02:48 UTC