Re: Interaction between minCount and hasValue

Hi Jose,

I think you can use a sh:filterShape to limit when your constraint applies.

Untested:

:UserShape
    a sh:Shape ;
     sh:property [
         sh:predicate :role ;
         sh:hasValue :User ;
         sh:filterShape [
             sh:property [
                 sh:predicate :role ;
                 sh:minCount 1 ;
             ] ;
         ]
     ]    .

The intention of the above is to say that the hasValue constraint only 
applies to instances where :role has at least one value.

Holger


On 11/5/2015 15:47, Jose Emilio Labra Gayo wrote:
> I would like to model optional properties which can appear or not, but 
> in case that they appear have a fixed value.
>
> For example, in ShEx, I can define the following shape:
>
> <UserShape> {
>    rdfs:label xsd:string,
>    ex:role ex:User ?
> }
>
> where ex:role is an optional property with a fixed value. If it 
> appears, it must be ex:User.
>
> My first thought is that the previous example could be represented in 
> Shacl as:
>
> :UserShape
>    a sh:Shape ;
>    sh:property [
>         sh:predicate rdfs:label ;
>         sh:datatype xsd:string ;
>         sh:minCount 1 ;
>         sh:maxCount 1 ;
>     ] ;
>     sh:property [
>         sh:predicate :role ;
>         sh:hasValue :User ;
>         sh:minCount 0 ;
>         sh:maxCount 1 ;
>     ]    .
>
> However,reading the spec, I am not sure about the interaction between 
> sh:minCount and sh:hasValue.
>
> It appears that if we include sh:minCount 0, the spec says: "If the 
> value is 0 then this constraint is always satisfied and so may be 
> omitted."
>
> However, the definition of sh:hasValue says: "A validation result must 
> be produced if there is no triple that has the focus node as its 
> subject, the |sh:predicate| as its predicate and the |sh:hasValue| as 
> its object." and the SPARQL query seems to raise an error in that 
> case, which means that the following instance data woud not be valid:
>
> :user1 rdfs:label "Student 2" .
>
> Is is possible to combine optional properties with fixed values as in 
> the previous example or is there another way to define it?
>
> -- 
> -- Jose Labra
>