Expressing mapping cardinality in ConceptAssociation

[ChLaaboudi]

Context

The NACE Rev.2 – NACE Rev.2.1 correspondence table specifies, for each xkos:ConceptAssociation, a mapping cardinality (e.g in the table below - typeOfCorrespondence 1:1, 2:1, 4:10). This information is crucial for understanding how concepts in one classification correspond to concepts in another.

Current Situation

• XKOS does not currently define a property to capture the mapping cardinality.
• We currently use <dct:type> with a literal value to encode the cardinality

Existing Implementation

We have developed a controlled SKOS code list for the four generic types of mapping cardinality:

• 1:1
• 1:n
• n:1
• n:m

Problem

There is no dedicated property in XKOS to:

• link an xkos:ConceptAssociation to a mapping cardinality defined in a controlled vocabulary, and
• optionally capture exact numeric ratios (e.g., 4:10) where needed.

Proposal

We suggest extending XKOS with a new property xkos:mappingCardinality

xkos:mappingCardinality a rdf:Property ;
rdfs:label "Mapping Cardinality"@en ;
rdfs:comment "Specifies the cardinality of an XKOS ConceptAssociation using a controlled vocabulary of mapping types."@en ;
rdfs:domain xkos:ConceptAssociation ;
rdfs:range skos:Concept

• This property would allow linking each xkos:ConceptAssociation to a SKOS concept representing the cardinality (from a code list).
• Alternatively, implementations could also use an additional data property (e.g., xkos:cardinalityExpression) to store an exact ratio such as 4:10 (instead of dct:type)

xkos:cardinalityExpression a rdf:Property ;
rdfs:label "Cardinality Expression"@en ;
rdfs:comment "Exact numeric ratio of the mapping (e.g., 1:4, 45:45)."@en ;
rdfs:domain xkos:ConceptAssociation ;
rdfs:range xsd:string

[nichtich]

You could reuse https://w3id.org/sssom/mapping_cardinality. The semantics of "mapping cardinality" is unclear still, as your example does not use RDF but a spreadsheet. I assume the mapping cardinality in example 19 would be "2:3", no? If so, the semantics must be connected to xkos:sourceConcept and xkos:targetConcept for consistency. I don't see the benefit of adding such property for redundant information because it opens the door to errors and inconsistencies. On the other hand SSSOM also has such property, but why?