Policy representation: refinement on action is not parsed correctly

[gkirtzou]

Bug Report

Describe the Bug

One of the most popular policies that would be used in data spaces is the one that regards payment obligation.
I tried the typical way that payment is represented in ODRL (inspired by Example 20 in the official odrl model page https://www.w3.org/TR/odrl-model/#duty-policy), which is defined as a refinement on the action of "odrl:compensate", but EDC cannot parse it properly and produces an error during policy creation.

Expected Behavior

ECD was expected to parse and store the following policy during policy creation:

{
    "@context": {
        "@vocab": "https://w3id.org/edc/v0.0.1/ns/",
        "edc": "https://w3id.org/edc/v0.0.1/ns/",
        "rdfs": "http://www.w3.org/2000/01/rdf-schema#",
        "dcat": "http://www.w3.org/ns/dcat#",
        "xsd": "http://www.w3.org/2001/XMLSchema#",
        "foaf": "http://xmlns.com/foaf/0.1/",
        "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
        "adms": "http://www.w3.org/ns/adms#",
        "dcmitype": "http://purl.org/dc/dcmitype/",
        "skos": "http://www.w3.org/2004/02/skos/core#",
        "dct": "http://purl.org/dc/terms/",
        "odrl": "http://www.w3.org/ns/odrl/2/",
        "owl": "http://www.w3.org/2002/07/owl#",
        "cc": "http://creativecommons.org/ns#",
        "dalicc": "https://dalicc.net/ns#",
        "dalicclib": "https://dalicc.net/licenselibrary/",
        "osl": "http://opensource.org/licenses/",
        "prov": "http://www.w3.org/ns/prov#",
        "spdx": "http://spdx.org/rdf/terms#",
        "example": "http://www.example.com/"
    },
    "policy": {
        "@type": "odrl:Set",
        "dct:description": {
            "@language": "en",
            "@value":"Payment Once - odrl:compensate"
        },
        "dct:title": {
            "@language": "en",
            "@value": "Payment Once - odrl:compensate"
        },
        "odrl:permission": [
            {
                "@type": "odrl:Permission",
                "odrl:action": {
                    "@id": "odrl:use"
                }
            }
        ],
        "odrl:obligation": [
            {
                "@type": "odrl:Duty",
                "odrl:action":
                {
                    "rdf:value": {
                      "@id": "odrl:compensate"
                    },
                    "odrl:refinement": [
                      {
                        "odrl:leftOperand": {
                            "@id": "odrl:payAmount"
                        },
                        "odrl:operator": {
                            "@id": "odrl:eq"
                        },
                        "odrl:rightOperand": {
                            "@type": "http://www.w3.org/2001/XMLSchema#decimal",
                            "@value": "100.0"
                          },
                        "odrl:unit": "http://dbpedia.org/resource/Euro"
                      }
                    ]
                }
            }
        ],
        "odrl:prohibition": null
    }
}

Observed Behavior

EDC returns the following error during creation:

  [ 
               {
                 "message": "Failed to construct instance: type",
                 "type": "InvalidRequest",
                 "path": null,
                 "invalidValue": null
               },
               {
                  "message": "ARRAY must be org.eclipse.edc.policy.model.Action but was: unknown",
                  "type": "InvalidRequest",
                  "path": null,
                  "invalidValue": null
              }
]

Context Information

Used version EDC v0.8.0

Possible Implementation

I believe the problem lies in the "rdf:value" property.

[jimmarino]

This is not a feature we will implement. The DSP specification profiles ODRL, meaning only a subset of the possible serializations are supported.

The specification group is currently refining its JSON Schemas to explicitly not require conformant implementations to support anything beyond the normative serialization.

An implementation may, of course, support this type of extensibility, but the EDC won't, so I am closing this.

[gkirtzou]

Thank you for clarifying these issues. Is it possible to point me to the documentation of the DSP specification profiles ODRL and the JSON Schemas from the specification group that the EDC is and will support, so that I can study them and see if and how an equivalent representation of this important policy for our dataspace could be represented within the limitations imposed by the DSP specification profiles ODRL and the EDC implementation?

Thank you in advance.