dcat-ap-SHACL.ttl uses <https://purl.eu/ns/shacl#message> instead of shacl:message for validation messages

[pmaria]

dcat-ap-SHACL.ttl uses <https://purl.eu/ns/shacl#message> instead of shacl:message for validation messages:

https://github.com/SEMICeu/DCAT-AP/blob/b9b20d1d25e6d827754e93af918344a46dc41a1b/releases/3.0.0/shacl/dcat-ap-SHACL.ttl#L73

Is this intended? https://purl.eu/ns/shacl#message is not dereferenceable.

[bertvannuffelen]

@pmaria This is due a limitation of SHACL specification, to enable multilingual messages in combination with the engine message.

SHACL specifies that shacl:message overwrites the message generated by the engine.

Thus for the constraint

https://semiceu.github.io//DCAT-AP/releases/3.0.0#AgentShape/236f0210baaf149903750c43bbe7012c21debb2a> 
   rdfs:seeAlso "https://semiceu.github.io//DCAT-AP/releases/3.0.0#Agent.type";
  shacl:description "A type of the agent that makes the Catalogue or Dataset available."@en;
  shacl:maxCount 1;
  shacl:name "type"@en;
  shacl:path dc:type.

and the data

<https://test.com/id/agent/1221> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://xmlns.com/foaf/0.1/Agent> .
<https://test.com/id/agent/1221> <http://xmlns.com/foaf/0.1/name> "agent 1"@en .
<https://test.com/id/agent/1221> <http://purl.org/dc/terms/type> "type ORG A".
<https://test.com/id/agent/1221> <http://purl.org/dc/terms/type> "type ORG B" . 

The SHACL engine will result a precise message that indicates there are 2 values, instead of 1. " Property may only have 1 value, but found 2" .

If you perform the replacement shacl:message, the message will be: "Maximally 1 values allowed for type".

This happens even if you add a shacl:message in another language that is not provided by the engine. The overwrite will happen.

As the engine message is more detailed and better pinpointing the error, but we also want to support multilingual messages we added an extra property.

You can try it with the ITB testbed which uses the reference SHACL library as it backbone.

• https://gist.github.com/bertvannuffelen/86cbaf4562f4fbb263f1828a8f9d6a3d : data
• https://gist.github.com/bertvannuffelen/e594fe7b1947aa2955a20954fa9ec463 : shacl snippet as is
• https://gist.github.com/bertvannuffelen/d219b727242d9a1e4ee063057d5d2959 : shacl snippet with replacement to shacl:message
• https://gist.github.com/bertvannuffelen/f1bdf56aa804e57f65c00c644fc271d4 : hacl snippet with replacement to shacl:message with dutch label.

Testbed Instance: https://www.itb.ec.europa.eu/shacl/any/upload.

[pmaria]

@bertvannuffelen thanks for the quick and clarifying response.

This might be an interesting issue to raise on https://github.com/w3c/shacl/issues for the possible new SHACL 1.2 WG.