Some inspiration from ShEx may help. The "validation" process is defined
by assigning triples to non-overlapping partitions defined by
constraints. There can be more then one way to partition the triples in
a disjunction or conjunction when there are multiple occurrences of
triples matching multiple constraints in the conjunction. OR and AND in
ShExC.
The process can involve backtracking to search through alternatives
(it's like string regex except "bag regex" is assigning triples to bags
as the regex passes over). It's also more "closed" by default in style.
SHACL does not have this "use once". The sub-shapes of a shape are more
independent. But it's only the compositional operations that matter =
not the basic triple constraints. And it matters less if what is being
extracted is a graph because it's a set.
Some restrictions are necessary - SHACL-SPARQL does say why a constraint
matched and can need the rest of the graph.
Andy
On 10/03/2022 19:19, Florian Kleedorfer wrote:
Not sure how that could work. You could keep a set of tiples per focus
node validation, add all triples that pass the constraint tests (given
that you somehow are able to reconstruct the triple(s) from the data the
Shacl logic is working on (which is not triples but, in many instances,
sets of nodes - e.g. the result of G.allSP()), and emit the set once
you've established that the complete shape is valid for the focus node.
I would be very sceptical of adding such a special-interest aspect to
code like SHACL that must be relied on and fast as can be.
Having said that, I've wanted to modify the way Jena evaluates SHACL
recently - maybe a way to extend it would be useful (allowing
inheritance or having some kind of callback or somesuch). However, I
found that for my use case, the trick with the graph wrapper that
observes which triples are pulled by SHACL works just fine and is very
simple to implement (the shacl validation algorithm, if you want to
modify it, is not that simple and easy to mess up).
Am 2022-03-09 14:26, schrieb Thomas Francart:
What is VLib.validateShape actually returns the focusNode + Path +
valueNodes that conform to each shape ? or emit them through a listener ?
(
https://github.com/apache/jena/blob/5ce8c141d425655bcaa9d7567117659e502a7ff1/jena-shacl/src/main/java/org/apache/jena/shacl/validation/VLib.java#L89
)
The idea would be to use the Validator as a "filter" that emits the
triples
valid according to shapes, so that they can be aggregated in an output
graph.
