How do you allow not foreseen properties in RDF when performing Shex validation?

Question

We are creating our Shex definition files checking that some IRIs are of a given type. There is no problem with our generated code but sometimes we get files generated using Protege and most of the individuals are of type X plus owl:NamedIndividual, making our validation fail because now a given resource has 2 assertions of type rdf:type.

Adding owl:NamedIndividual to all shape checks seems like polluting the Shape definition, so how would you allow extra properties that do not conflict with your shape definition?

Answer 1

In Shex, by default the triple constraints are closed which means that a shape like:

:Shape {
  rdf:type [ :X ]
}

means that a node that conforms to :Shape must have exactly one rdf:type declaration whose value is :X.

If you want to allow extra values for the rdf:type declaration, you can express it with the keyword EXTRA as:

:Shape EXTRA rdf:type {
 rdf:type [ :X ]
}

The meaning now is that a conforming node must have rdf:type :X and can have zero or mode values for rdf:type.

Notice that the previous example could be defined as:

:Shape EXTRA a {
 a [ :X ]
}

In the particular case that you only want to allow an extra rdf:type with value owl:NamedIndividual you could also define it as:

:Shape {
 a [:X ] ;
 a [ owl:NamedIndividual] ;
}

or as:

:Shape {
 a [:X owl:NamedIndividual]{2} ;
}