The First Public Working Draft of SHACL (SHApes Constraint Language) has
been released.[1] I did a brief blog post introducing SHACL and asking
for comments and for good test examples.[2] I will do another blog post
on issues and specific questions, but can already add a few here below.
I reiterate that comments from the DC community are very important
because most Working Group members are only interested in tightly
controlled enterprise systems, not in open data sharing. It's the latter
perspective that we bring.
A FEW ISSUES
"1.1 Relationship between SHACL and RDFS
SHACL uses RDF and RDFS vocabulary (in particular rdf:type, rdfs:Class,
rdfs:subClassOf, rdfs:label, rdfs:comment, rdf:Property, rdf:List,
rdf:langLiteral, and rdfs:Resource) and notions (notably classes,
instances, and subclasses). However, SHACL does not use this vocabulary
or these notions in the way that they are defined in RDF and RDFS
[rdf11-mt]."
**This strikes me as a really bad idea, but the specific differences
(which are in the remaining paragraphs of that section) may not be
important.
"ISSUE 23: Classes and/or Shapes
There is no agreement in the WG on the relationship between sh:Shape and
rdfs:Class. In the absence of such an agreement, this document uses
sh:Shape in most examples but allows classes to be also shapes, with the
class sh:ShapeClass as syntactic sugar."
**The main author of the report prefers that classes themselves can be
defined as shapes, thus taking on both roles. So a class like
foaf:Person would be defined as a particular shape (aka set of
constraints on the instance) rather than creating a class ex:PersonShape
and associating that with foaf:Person. Others object to this overloading.
"5. Validation Results Vocabulary"
**There was a requirement that came from this community that it should
be possible to set a variety of validation responses. See this section
5; it has three levels of severity: info, warning, violation. Those can
be subclassed. Is that going to be sufficient for us? What level of
detail is needed for violation responses?
If you don't wish to subscribe to the WG list, you can follow the public
archive.[3] There has been one comment already,[4] and it mentioned DC
properties as a substitute for some rdf properties, which hadn't
occurred to me. Interesting.
kc
[1] http://www.w3.org/TR/2015/WD-shacl-20151008/
[2] http://kcoyle.blogspot.com/2015/10/shacl-shapes-constraint-language.html
[3] https://lists.w3.org/Archives/Public/public-data-shapes-wg/
[4]
https://lists.w3.org/Archives/Public/public-data-shapes-wg/2015Oct/0085.html
--
Karen Coyle
[log in to unmask] http://kcoyle.net
m: 1-510-435-8234
skype: kcoylenet/+1-510-984-3600
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