Metadata-schema extension mechanism

[dennisvang]

In SHACL we can re-use node shapes by basing a sh:NodeShape on one or more other node shapes, with the help of sh:node.

For example:

@prefix ex: <http://example.org/ns#> .
@prefix sh: <http://www.w3.org/ns/shacl#> .

ex:BaseShape1 a sh:NodeShape ;
    sh:targetClass ex:Base ;
    sh:property [
        sh:path ex:baseProperty1 ;
        sh:minCount 1 ;
    ] .


ex:BaseShape2 a sh:NodeShape ;
    sh:targetClass ex:Base ;
    sh:property [
        sh:path ex:baseProperty2 ;
        sh:minCount 1 ;
    ] .


ex:ExtendedShape a sh:NodeShape ;
    sh:targetClass ex:Extended ;
    sh:node ex:BaseShape1 ;
    sh:node ex:BaseShape2 ;
    sh:property [
        sh:path ex:extraProperty ;
        sh:minCount 1 ;
    ] .

(a similar thing can be done with sh:property and sh:PropertyShape)

However, in the FDP, the SHACL above does not work.

Instead, we need to add base shapes via the extends property in the JSON body that is posted to the FDP API. This is rendered in the client using a dropdown:

Not sure why schema-extension is implemented this way (maybe just to enable the use of a dropdown in the client), but the fact that the SHACL above does not work in the FDP is inconvenient. The extension mechanism is quite obscure.

Extending shapes via sh:node should also be supported.

[dennisvang]

If we inspect the actual SHACL used by the FDP according to the profile, it turns out it does not use the SHACL node shape extension mechanism in the expected way.

For example, from the default FDP v1.18.2 running locally, following the link from the profile:

click to see screenshot

http://localhost/metadata-schemas/a92958ab-a414-47e6-8e17-68ba96ba3a2b?format=ttl

We can see that the AgentShape is reused for the publisher property, using sh:node, but, then again, the FDPShape does not reuse ResourceShape. Instead, they are just separate subjects.

click to see SHACL

@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix dcat: <http://www.w3.org/ns/dcat#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix ldp: <http://www.w3.org/ns/ldp#> .

<http://fairdatapoint.org/FDPShape> a <http://www.w3.org/ns/shacl#NodeShape>;
  <http://www.w3.org/ns/shacl#targetClass> <https://w3id.org/fdp/fdp-o#FAIRDataPoint>;
  <http://www.w3.org/ns/shacl#property> [
      <http://www.w3.org/ns/shacl#path> <https://w3id.org/fdp/fdp-o#startDate>;
      <http://www.w3.org/ns/shacl#datatype> xsd:date;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#DatePickerEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LiteralViewer>;
      <http://www.w3.org/ns/shacl#order> 40
    ], [
      <http://www.w3.org/ns/shacl#path> <https://w3id.org/fdp/fdp-o#endDate>;
      <http://www.w3.org/ns/shacl#datatype> xsd:date;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#DatePickerEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LiteralViewer>;
      <http://www.w3.org/ns/shacl#order> 41
    ], [
      <http://www.w3.org/ns/shacl#path> <https://w3id.org/fdp/fdp-o#uiLanguage>;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#IRI>;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://www.w3.org/ns/shacl#defaultValue> <http://id.loc.gov/vocabulary/iso639-1/en>;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#URIEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LabelViewer>;
      <http://www.w3.org/ns/shacl#order> 42
    ], [
      <http://www.w3.org/ns/shacl#path> <https://w3id.org/fdp/fdp-o#metadataIdentifier>;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#IRI>;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#URIEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LabelViewer>;
      <http://www.w3.org/ns/shacl#order> 43
    ], [
      <http://www.w3.org/ns/shacl#path> <https://w3id.org/fdp/fdp-o#metadataIssued>;
      <http://www.w3.org/ns/shacl#datatype> xsd:dateTime;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LiteralViewer>
    ], [
      <http://www.w3.org/ns/shacl#path> <https://w3id.org/fdp/fdp-o#metadataModified>;
      <http://www.w3.org/ns/shacl#datatype> xsd:dateTime;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LiteralViewer>
    ] .

<http://fairdatapoint.org/MetadataServiceShape> a <http://www.w3.org/ns/shacl#NodeShape>;
  <http://www.w3.org/ns/shacl#targetClass> <https://w3id.org/fdp/fdp-o#MetadataService> .

<http://fairdatapoint.org/DataServiceShape> a <http://www.w3.org/ns/shacl#NodeShape>;
  <http://www.w3.org/ns/shacl#targetClass> dcat:DataService;
  <http://www.w3.org/ns/shacl#property> [
      <http://www.w3.org/ns/shacl#path> dcat:endpointURL;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#IRI>;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://www.w3.org/ns/shacl#order> 20
    ], [
      <http://www.w3.org/ns/shacl#path> dcat:endpointDescription;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#Literal>;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#TextAreaEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LiteralViewer>;
      <http://www.w3.org/ns/shacl#order> 21
    ] .

<http://fairdatapoint.org/ResourceShape> a <http://www.w3.org/ns/shacl#NodeShape>;
  <http://www.w3.org/ns/shacl#targetClass> dcat:Resource;
  <http://www.w3.org/ns/shacl#property> [
      <http://www.w3.org/ns/shacl#path> dcterms:title;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#Literal>;
      <http://www.w3.org/ns/shacl#minCount> 1;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#TextFieldEditor>;
      <http://www.w3.org/ns/shacl#order> 1
    ], [
      <http://www.w3.org/ns/shacl#path> dcterms:description;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#Literal>;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#TextAreaEditor>;
      <http://www.w3.org/ns/shacl#order> 2
    ], [
      <http://www.w3.org/ns/shacl#path> dcterms:publisher;
      <http://www.w3.org/ns/shacl#node> <http://fairdatapoint.org/AgentShape>;
      <http://www.w3.org/ns/shacl#minCount> 1;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#BlankNodeEditor>;
      <http://www.w3.org/ns/shacl#order> 3
    ], [
      <http://www.w3.org/ns/shacl#path> dcat:version;
      <http://www.w3.org/ns/shacl#name> "version";
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#Literal>;
      <http://www.w3.org/ns/shacl#minCount> 1;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#TextFieldEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LiteralViewer>;
      <http://www.w3.org/ns/shacl#order> 4
    ], [
      <http://www.w3.org/ns/shacl#path> dcterms:language;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#IRI>;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#URIEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LabelViewer>;
      <http://www.w3.org/ns/shacl#defaultValue> <http://id.loc.gov/vocabulary/iso639-1/en>;
      <http://www.w3.org/ns/shacl#order> 5
    ], [
      <http://www.w3.org/ns/shacl#path> dcterms:license;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#IRI>;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#URIEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LabelViewer>;
      <http://www.w3.org/ns/shacl#defaultValue> <http://purl.org/NET/rdflicense/cc-zero1.0>;
      <http://www.w3.org/ns/shacl#order> 6
    ], [
      <http://www.w3.org/ns/shacl#path> dcterms:rights;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#IRI>;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#URIEditor>;
      <http://datashapes.org/dash#viewer> <http://datashapes.org/dash#LabelViewer>;
      <http://www.w3.org/ns/shacl#order> 7
    ] .

<http://fairdatapoint.org/AgentShape> a <http://www.w3.org/ns/shacl#NodeShape>;
  <http://www.w3.org/ns/shacl#targetClass> foaf:Agent;
  <http://www.w3.org/ns/shacl#property> [
      <http://www.w3.org/ns/shacl#path> foaf:name;
      <http://www.w3.org/ns/shacl#nodeKind> <http://www.w3.org/ns/shacl#Literal>;
      <http://www.w3.org/ns/shacl#minCount> 1;
      <http://www.w3.org/ns/shacl#maxCount> 1;
      <http://datashapes.org/dash#editor> <http://datashapes.org/dash#TextFieldEditor>
    ] .