This is in continuation of my email [1] in which I have outlined a
simpler constraints metamodel that can serve as a "schema" for SHACL
that is friendly both to RDFS/OWL and SHACL tools.
The attached file is a quick draft for an RDFS model of SHACL shapes and
constraints. I have also attached a few diagrams to explain how this
would work.
Image 1 illustrates the classes sh:Shape and sh:Constraint, with its 3
subclasses for property, inverseProperty and general node constraints).
Image 2 introduces the class sh:ConstraintType (similar to Arthur's
Assertion class, aka templates), which groups together the arguments of
a constraint type (such as sh:minCount for sh:MinCountConstraint).
Furthermore, ConstraintTypes link to Validators, which provide the
executable semantics. SPARQL is one kind of validators,
NodeValidationFunction is another:
- General SPARQL validators can contain an arbitrary SELECT query,
returning one row for each violation. That is needed for complex cases
like sh:minCount, QCRs, and sh:hasValue
- NodeValidationFunctions are simplified ASK queries that take a single
node as parameter and check whether that node matches a condition, e.g.
a given regular expression sh:pattern.
Image 3 shows two examples of such sh:ConstraintTypes
(sh:MinCountConstraint and sh:PatternConstraint). They serve as
superclasses of sh:PropertyConstraint etc so that their properties can
be accumulated in a single node. As you can see, the structure of
constraint types such as sh:MinCountConstraint can be reused in multiple
places.
Regards,
Holger
[1[
https://lists.w3.org/Archives/Public/public-data-shapes-wg/2015Nov/0163.html
