In ISO 19115, conformity is expressed as a result of a test that states whether data are or not conformat wrt a given specification. In addition to this, INSPIRE adds another possible result, namely, "not evaluated".

Property dct:conformsTo (available in DCAT-AP) can model just one case - i.e., when the test result confirms that data are conformant.

The proposed solution is meant to preserve the semantics of element "conformity" in ISO 19115 and INSPIRE metadata, and to be at the same time compatible with DCAT-AP.

So, the general solution proposed to model conformity is to use the EARL vocabulary, which is designed to report the results of a test against a specification. Moreover, when the result of the test is positive ("data are conformant") and only in this case, the proposal is to specify also a dct:conformsTo statement.

To take a decision, it would be important to know which are the existing practices for modelling the ISO 19115 / INSPIRE notion of "conformity" in RDF.

An alternative option is to use the PROV ontology.

Based on feedback from the W3C PROV WG (see the relevant thread), the example in the original post can be re-written as follows:

was:describedby [
  a prov:Activity;
# Conformity degree  
  prov:generated <http://inspire.ec.europa.eu/codelist/DegreeOfConformity/conformant>
  prov:qualifiedAssociation [
    prov:hadPlan [
      a prov:Plan;
      prov:wasDerivedFrom [
# Specification
        a prov:Entity, dct:Standard;
        dct:title "COMMISSION REGULATION (EC) No 976/2009 of 19 October 2009 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards the Network Services"@en
        dct:issued "2009-10-20"^^xsd:date
      ]
    ];
  ];
] .
 

During the 4th WG meeting of 20 May 2015, it was decided by vote that the proposal to use the PROV ontology to represent conformance results is accepted. This decision was taken alongside with the issue GeoDCAT-AP - How to encode metadata elements on data quality?.

There is an explanation of the decision taken in the last version of the GeoDCAT-AP specifications.

The GeoDCAT-AP specification only provides a syntax binding for conformity and not for data quality in general. In ISO 19115 conformance and quality information is encoded as a quality report containing the result of a test (an evaluation) of a given quality measure  according to an evaluation method with a quantitative result (a metric) or a conformance result (pass or fail) as most important outcome. For encoding conformance, GeoDCAT-AP proposes to use dct:conformsTo and the W3C Provenance Ontology (PROV-O) as explained in the following paragraphs. For encoding other aspects of data quality, GeoDCAT-AP does not provide a syntax binding as there is a risk that the (future) work of other standards bodies on data quality may make the proposed syntax binding for GeoDCAT-AP outdated. For example, the W3C Data on the Web Best Practices WG is working on a Data Quality standard. To limit the impact, it may be better to only provide a partial mapping for Data Quality / Conformance.

DCAT-AP provides a single candidate, dct:conformsTo, which however can be used to map only a conformity of degree ‘conformant’. This is suitable for GeoDCAT-AP Core.

Considering how conformity must be expressed in GeoDCAT-AP Extended (see the INSPIRE Metadata Regulation, Part B, §7), possible candidates are the W3C Evaluation and Report Language (EARL) and the W3C Provenance Ontology (PROV-O). The latter candidate was chosen since it would enable wider re-use with respect to the EARL vocabulary, which is more specific, and its use is limited. PROV-O allows encoding conformity as a test activity (prov:Activity) that generated a result encoded with property ‘prov:generated’, corresponding to the degree of conformity, for which the INSPIRE Registry maintains a URI set, see Section 6 of the document. The specification against which the conformance is asserted is encoded via a qualified association (prov:QualifiedAssociation) with a test plan (a prov:Plan) in turn derived from a standard (dct:Standard, also prov:Entity). These associations are made via a chain of properties: ‘prov:qualifiedAssociation’, ‘prov:hadPlan’, and ‘prov:wasDerivedFrom’. 

In order to grant interoperability with DCAT-AP, when conformity is of degree “conformant”, the proposal is to use both PROV-O and dct:conformsTo for GeoDCAT-AP Extended.

# Resource metadata in GeoDCAT-AP
prov:wasUsedBy [
 a prov:Activity;
# Conformity degree
  prov:generated [
   dct:type <http://inspire.ec.europa.eu/codelist/DegreeOfConformity/conformant> ;
   dct:description “See the referenced specification”@en
  prov:qualifiedAssociation [
   prov:hadPlan [
     a prov:Plan;
     prov:wasDerivedFrom [
# Specification
        a prov:Entity, dct:Standard;
       dct:title "COMMISSION REGULATION (EC) No 976/2009 of 19 October 2009 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards the Network Services"@en
       dct:issued "2009-10-20"^^xsd:date
     ]
   ];
 ];
] .