Multiple language tags trigger SHACL violation for multiple values

[schivmeister]

This has been a long-standing issue, not least due to the rdf:PlainLiteral (more recently xsd:string) and rdfs:langString dichotomy in ontologies like ePO, whose constraints are generated by model2owl. Having data like the following:

epd:id_d9997c19-6dd6-43e2-9706-28df10f8f1eb_AwardCriterion_Y6iaTUeQDukaqhJjdTfKhV
  a epo:AwardCriterion;
  epo:hasAwardCriterionType <http://publications.europa.eu/resource/authority/award-criterion-type/quality>;
  epo:hasWeightValueType <http://publications.europa.eu/resource/authority/number-weight/per-exa>;
  cccev:weight 10.0;
  dct:description "See purchase documents"@en, "Nurodyta pirkimo dokumentuose"@lt;
  skos:prefLabel "Delivery time for goods"@en, "Delivery time for goods"@lt .

will raise a sh:MaxCountConstraintComponent ("More than 1 values") violation for dct:description and/or skos:prefLabel.

There is a simple fix to this: sh:uniqueLang true

However, that's not the whole story. There is a more sophisticated variant which allows also plain, non-language-tagged literals to co-exist with language-tagged ones, combining sh:uniqueLang and sh:qualifiedValueShape:

ex:MaxOneRDFLabelShape
  a sh:NodeShape ;
  sh:targetSubjectsOf rdf:type ;
  sh:property [
    sh:path rdfs:label ;
    sh:uniqueLang true ;
  ] ;
  sh:property [
    sh:path rdfs:label ;
    sh:qualifiedMaxCount 1 ;
    sh:qualifiedValueShape [
      sh:datatype xsd:string ;
    ] ;
    sh:message "Violation of standard practice: More than one `rdfs:label` exists without a language tag" ;
  ]
.

This was implemented for the SEMIC validator (see shape and accompanying test data).

The above technique would allow the following to pass:

ex:Note a owl:Class ;
  skos:prefLabel "note"@en , "nota"@es ;
  rdfs:label "note"@en , "nota"@es ;
  rdfs:comment "note" , "notee" .

but not:

ex:Note a owl:Class ;
  skos:prefLabel "note" , "notee" , "note"@en , "notee"@en ;
  rdfs:label "note" , "notee" , "note"@en , "notee"@en .

The technique currently seen with sh:or:

...
	sh:minCount 0 ;
	sh:maxCount 1 ;
	sh:or (
		[
			sh:datatype xsd:string ;
		]
		[
			sh:datatype rdf:langString ;
		]
	) .

as implemented based on #219, does not work for multiple language tags.

Whether to implement the simple or advanced variant allowing co-existence of plain and language-tagged literals, is perhaps a question for the ontology stakeholders.

[cristianvasquez]

Thanks @schivmeister for pointing out and providing a working solution.

Regarding the properties you mentioned, skos:prefLabel and dct:description:

• For skos:prefLabel, its semantics are well-defined, it can have multiple language variants, but strictly one per language (source).
• In contrast, dct:description does not have this restriction

This distinction is to be declared explicitly by the ontology stakeholders in their model.

To define these specifics, Model2OWL could enable the definition of a basic set of datatype extensions via shapes, similar to the ones you shared.

Some of these shapes might be common enough that they should be included by default with Model2OWL.