Annotating Hydra collection search template with SHACL Advanced Features

readme.md

This is an idea for how SHACL AF Node Expression can be used to annotate a hydra search template so that values coming from the request query string would be transformed to SPARQL patterns an injeced into the resulting query

The collection resource <shapes> supports a targetNode query string parameter which should be translated to a SPARQL union like below. The $this token will represent each collection member (instance of shape). For example, when requesting shapes?targetNode=foobar, the generated patterns could be:

{
  # query the target node directly
  $this sh:targetNode <foobar>
}
UNION
{
  # or find shapes which target foobar's classes
  $this sh:targetClass/^rdf:type <foobar> .
}

This would be equivalent to this filter shape

[
  sh:filterShape [
    sh:property [
      sh:path [
        sh:union (
          [ sh:path sh:targetNode ]
          [
            sh:nodes [ sh:path sh:targetClass ] ;
            sh:path [ sh:inversePath rdf:type ] ;
          ]
        ) ;
      ] ;
      sh:hasValue <foobar> ;
    ] ;
  ] ;
] .

shapes.ttl

<shapes> a hydra:Collection ;
  hydra:search [
    hydra:template "{?targetNode}" ;
    hydra:mapping [
      hydra:variable "targetNode" ;
      hydra:property sh:targetNode ;
      # the object of `query:filter` must be a Node Expression
      query:filter [
        sh:union (
          [ sh:path sh:targetNode ]
          [ 
            sh:nodes [ sh:path sh:targetClass ] ;
            sh:path [ sh:inversePath rdf:type ] ;
          ]
        ) ;
      ] ;
    ] ;
  ] ;
.