Add RDF support

[mhrimaz]

RDF is also part of the specification. It would be great to add support to handle RDF representation of AAS.

[mristin]

@mhrimaz We already generate RDF+SHACL schemas. Could you please clarify?

[mhrimaz]

I don't mean the ontology and SHACL. I mean handling the RDF serialization so you can also load a RDF file like:

@prefix aas: <https://admin-shell.io/aas/3/0/> .

<MySubmodel> a aas:Submodel ;
    <https://admin-shell.io/aas/3/0/Identifiable/id> "MySubmodel" .

and convert it to JSON or vice versa.

{
  "id": "MySubmodel",
  "modelType": "Submodel"
}

[wiresio]

We recently added generation of JSON-LD context. We it, you can do:

<urn:aas> aas:Environment\/submodels <urn:sub> ; a aas:Environment .
<urn:sub> aas:Referable\/idShort "MySubmodel" ; a aas:Submodel .

Convert to JSON-LD and then do a JSON-LD framing with:

{
  "@context": {GENERATEDCONTEXT},
  "Environment/submodels": {}
}

[mhrimaz]

@wiresio that's great!

I couldn't find anything related to json-ld in the current python. Are you guys planning to add it?

And other than generation of JSON-LD (RDF Turtle), is that possible to read RDF Turtle (JSON-LD) data ?

[wiresio]

Please take a look at:

• https://github.com/aas-core-works/aas-core-codegen/tree/main/aas_core_codegen/jsonld
• https://github.com/aas-core-works/aas-core-codegen/tree/main/test_data/jsonld_context

For everything related to JSON-LD, please see: https://json-ld.org/#developers

[mhrimaz]

We recently added generation of JSON-LD context. We it, you can do:

<urn:aas> aas:Environment\/submodels <urn:sub> ; a aas:Environment .
<urn:sub> aas:Referable\/idShort "MySubmodel" ; a aas:Submodel .

How can I generate the provided triple? are they now part of the generated SDKs? I would appreciate if you can provide an example.

The provided file that you sent is the definition of elements and the relations between them. similar to the rdf-ontology.

So my question is how to convert a Submodel to json-ld and read it?

Here a example Submodel in json-ld:

[
  {
    "@id":"https://admin-shell.io/aas/3/0/Submodel"
  },
  {
    "@id":"urn:sub",
    "https://admin-shell.io/aas/3/0/Identifiable/id":[
      {
        "@value":"MySubmodel"
      }
    ],
    "@type":[
      "https://admin-shell.io/aas/3/0/Submodel"
    ]
  }
]

or in RDF turtle:

@prefix aas: <https://admin-shell.io/aas/3/0/> .

<urn:sub> aas:Identifiable\/id "MySubmodel" ; 
a aas:Submodel .

or in JSON turtle:

{
  "id": "MySubmodel",
  "modelType": "Submodel"
}

[wiresio]

PREFIX aas: <https://admin-shell.io/aas/3/0/>
<urn:aas> aas:Environment\/submodels <urn:sub> ; a aas:Environment .
<urn:sub> aas:Referable\/idShort "MySubmodel" ; a aas:Submodel .

results in:

{
  "@graph": [
    {
      "@id": "urn:sub",
      "aas:Referable/idShort": "MySubmodel",
      "@type": "aas:Submodel"
    },
    {
      "@id": "urn:aas",
      "@type": "aas:Environment",
      "aas:Environment/submodels": {
        "@id": "urn:sub"
      }
    }
  ],
  "@context": {
    "aas": "https://admin-shell.io/aas/3/0/"
  }
}

When you frame it, you get:

...
  },
  "@id": "urn:aas",
  "modelType": "Environment",
  "submodels": [
    {
      "@id": "urn:sub",
      "modelType": "Submodel",
      "idShort": "MySubmodel"
    }
  ]
}

You can try it here: https://json-ld.org/playground/

[mristin]

@mhrimaz wrote:

I mean handling the RDF serialization so you can also load a RDF file [...]

There are no RDF modules in all of standard libraries, so this makes it a no-go for the current core SDKs which aim at zero or few dependencies.

I would be glad to mentor the pull request if somebody wants to write a generator for an RDF de/serializer and publish the generated code as a separate package.

[mhrimaz]

@wiresio I think you are one step ahead. What is missing is the step before it. converting objects to rdf.

Key simpleKey = new DefaultKey.Builder()
                .value("simple")
                .type(KeyTypes.GLOBAL_REFERENCE)
                .build();
// This part is not in AAS4j, implemented by me. Model is a Apache Jena model.
RDFSerializationResult rdfSerializationResult = new DefaultKeyRDFHandler().toModel(simpleKey);
rdfSerializationResult.getModel().write(System.out, Lang.TTL.getName());

which produce the following RDF Turtle:

[ a       <https://admin-shell.io/aas/3/0/Key>;
  <https://admin-shell.io/aas/3/0/Key/type>
          "GLOBAL_REFERENCE";
  <https://admin-shell.io/aas/3/0/Key/value>
          "simple"
] .

Or with aas-core3.0-python:

import json
import aas_core3.types as aas_types
import aas_core3.verification as aas_verification
import aas_core3.jsonization as aas_jsonization
import aas_core3.xmlization as aas_xmlization

example = aas_types.Submodel(id="some-unique-global-identifier")
print(aas_jsonization.to_jsonable(example)) # as json
print(aas_xmlization.to_str(example))# as xml


aas_rdfization.to_turtle() # as rdf turtle or json-ld is missing!

[wiresio]

I think you are one step ahead. What is missing is the step before it. converting objects to rdf.

That's right. I thought it was your starting point.

[mristin]

I'm closing the issue due to inactivity -- I don't think we are going to work on this feature in the near or mid-term. The specification for RDF+SHACL is in progress of substantial improvement (e.g., see: admin-shell-io/aas-specs#421), so once the changes are fleshed out, we can re-consider and re-open this issue.