introduce ec:hasAlternativeContentDescription / ec:AlternativeContentDescription / ec:alternativeContentDescriptionTypes

[wivaku]

From discussions with the EBU maintenance team it is my understanding it is being considered to use the same approach for alternative descriptions and for alternative titles.

This instead of the current description approach (see #424).
Note: it is assumed the following are not intended as (alternative) content descriptions: ec:abstract, ec:summary, ec:synopsis.

I imagine it will look something like the below (similar to ec:hasAlternativeTitle, ec:AlternativeTitle, ec:alternativeTitleTypes):

ec:hasAlternativeContentDescription rdf:type owl:ObjectProperty ;
  rdfs:label "has alternative description"@en .

ec:AlternativeContentDescription rdf:type owl:Class ;
  rdfs:subClassOf [ rdf:type owl:Restriction ;
                    owl:onProperty ec:hasIdentifier ;
                    owl:allValuesFrom ec:Identifier
                  ] ,
                  [ rdf:type owl:Restriction ;
                    owl:onProperty ec:hasObjectType ;
                    owl:allValuesFrom skos:Concept
                  ] ,
                  [ rdf:type owl:Restriction ;
                    owl:onProperty ec:hasEndDateTime ;
                    owl:maxQualifiedCardinality "1"^^xsd:nonNegativeInteger ;
                    owl:onClass time:Instant
                  ] ,
                  [ rdf:type owl:Restriction ;
                    owl:onProperty ec:hasStartDateTime ;
                    owl:maxQualifiedCardinality "1"^^xsd:nonNegativeInteger ;
                    owl:onClass time:Instant
                  ] ,
                  [ rdf:type owl:Restriction ;
                    owl:onProperty ec:title ;
                    owl:someValuesFrom rdfs:Literal
                  ] ,
                  [ rdf:type owl:Restriction ;
                    owl:onProperty ec:description ;
                    owl:allValuesFrom rdfs:Literal
                  ] ,
                  [ rdf:type owl:Restriction ;
                    owl:onProperty ec:name ;
                    owl:allValuesFrom rdfs:Literal
                  ] ;
  rdfs:label "Alternative description"@en .

ec:EditorialObject rdfs:subClassOf
    [ rdf:type owl:Restriction ;
      owl:onProperty ec:hasAlternativeContentDescription ;
      owl:allValuesFrom ec:AlternativeContentDescription
    ] .

ec:PublicationEvent rdfs:subClassOf
    [ rdf:type owl:Restriction ;
      owl:onProperty ec:hasAlternativeContentDescription ;
      owl:allValuesFrom ec:AlternativeContentDescription
    ] .

# Individuals

ec:alternativeContentDescriptionTypes rdf:type owl:NamedIndividual, skos:ConceptScheme ;
  skos:prefLabel "Alternative description types"@en .

ec:mediumDescription rdf:type owl:NamedIndividual, skos:Concept ;
  skos:inScheme ec:alternativeContentDescriptionTypes ;
  skos:definition "The medium description of the work."@en ;
  skos:prefLabel "Medium description"@en .

ec:shortDescription rdf:type owl:NamedIndividual, skos:Concept ;
  skos:inScheme ec:alternativeContentDescriptionTypes ;
  skos:definition "The short description of the work."@en ;
  skos:prefLabel "Short description"@en .

ec:kickerDescription rdf:type owl:NamedIndividual, skos:Concept ;
  skos:inScheme ec:alternativeContentDescriptionTypes ;
  skos:definition "The kicker (one-liner) description of the work."@en ;
  skos:prefLabel "Kicker description"@en .