Don't use relators as property but indicate relator via "role" property

[acka47]

As discussed in #10 , we will indicate the roles of a contributor in the contributor object with the "role" property and won't use relators as properties.

Example:

{
  "@context": {
    "id": "@id",
    "type": "@type",
    "role": "http://bibframe.org/vocab/relator",
    "contributor": {
      "@type": "@id",
      "@id": "http://purl.org/dc/terms/contributor",
      "@container": "@set"
    },
    "label": "http://www.w3.org/2000/01/rdf-schema#label",
    "altLabel": "http://www.w3.org/2004/02/skos/core#altLabel",
    "subject": {
      "@type": "@id",
      "@id": "http://purl.org/dc/terms/subject",
      "@container": "@list"
    }
  },
  "@id" : "http://lobid.org/resources/HT018843259#!",
  "contributor": [ {
    "id": "http://d-nb.info/gnd/118548018",
    "type": "DifferentiatedPerson",
    "role": {
      "id": "http://id.loc.gov/vocabulary/relators/cre",
      "label": "Autor/in"
    },
    "label": "Becker, Thomas Paul",
    "altLabel": [ "Becker, Thomas P." ]
  } ],
  "subject": [ {
     "id" : "http://d-nb.info/gnd/4031485-6",
     "type": "PlaceOrGeographicName",
     "label": "Erzstift Köln",
     "altLabel": [ "Kölner Krieg", "Truchsessischer Krieg" ]
  } ]
}

We won't be able to only use a string as value for "role" as proposed in #10 but will – as you can see in the example – also use the side car approach here – giving us presentation labels for the different roles in the data.

[acka47]

@jschnasse just pointed out that the approach we chose above is not correct as it associates the role with the person. As the role is a relation between the person and the resource this has to somehow be made clear. Taking a look at Bibframe 2.0, it seems to be a reasonable approach. An example from http://www.loc.gov/bibframe/docs/pdf/bf2-roles-apr2016.pdf:

<http://bibframe.example.org/resource> bf:contribution [
    a bf:Contribution ;
    bf:role “illustrator” ;
    bf:agent <http://id.loc.gov/rwo/agents/n94064763> ] .

For the example above, the result would look like this:

{
  "@context": {
    "id": "@id",
    "type": "@type",
    "agent": "http://bibframe.org/vocab/agent",
    "role": "http://bibframe.org/vocab/relator",
    "conbtribution": "http://bibframe.org/vocab/contribution",
    "Contribution": "http://bibframe.org/vocab/Contribution",
    "label": "http://www.w3.org/2000/01/rdf-schema#label",
    "altLabel": "http://www.w3.org/2004/02/skos/core#altLabel",
    "subject": {
      "@type": "@id",
      "@id": "http://purl.org/dc/terms/subject",
      "@container": "@list"
    }
  },
  "id" : "http://lobid.org/resources/HT018843259#!",
  "contribution": [ {
    "type": "Contribution",
    "role": {
    "id": "http://id.loc.gov/vocabulary/relators/cre",
    "label": "Autor/in"
    },
    "agent": {
      "id": "http://d-nb.info/gnd/118548018",
      "type": "DifferentiatedPerson",
      "label": "Becker, Thomas Paul",
      "altLabel": [ "Becker, Thomas P." ]
      }
  } ],
  "subject": [ {
     "id" : "http://d-nb.info/gnd/4031485-6",
     "type": "PlaceOrGeographicName",
     "label": "Erzstift Köln",
     "altLabel": [ "Kölner Krieg", "Truchsessischer Krieg" ]
  } ]
}

[acka47]

Here is an example with multiple contributions:

{
   "@context":{
      "id":"@id",
      "type":"@type",
      "agent":"http://bibframe.org/vocab/agent",
      "role":"http://bibframe.org/vocab/relator",
      "contribution":"http://bibframe.org/vocab/contribution",
      "Contribution":"http://bibframe.org/vocab/Contribution",
      "label":"http://www.w3.org/2000/01/rdf-schema#label",
      "altLabel":"http://www.w3.org/2004/02/skos/core#altLabel",
      "subject":{
         "@type":"@id",
         "@id":"http://purl.org/dc/terms/subject",
         "@container":"@list"
      }
   },
   "id":"http://lobid.org/resources/HT019093814#!",
   "contribution":[
      {
         "type":"Contribution",
         "role":{
            "id":"http://id.loc.gov/vocabulary/relators/pht",
            "label":"Fotografie"
         },
         "agent":{
            "id":"http://d-nb.info/gnd/1067217789",
            "label":"Ganslmeier, Jakob",
            "type":[
               "Person"
            ]
         }
      },
      {
         "type":"Contribution",
         "role":{
            "id":"http://id.loc.gov/vocabulary/relators/pht",
            "label":"Fotografie"
         },
         "agent":{
            "id":"http://d-nb.info/gnd/1108328849",
            "label":"Boeszoermeny, Louisa",
            "type":[
               "Person"
            ]
         }
      },
      {
         "type":"Contribution",
         "role":{
            "id":"http://id.loc.gov/vocabulary/relators/ctb",
            "label":"Mitwirkung"
         },
         "agent":{
            "id":"http://d-nb.info/gnd/5555595-0",
            "label":"Kultur Ruhr GmbH",
            "type":[
               "CorporateBody"
            ]
         }
      },
      {
         "type":"Contribution",
         "role":{
            "id":"http://id.loc.gov/vocabulary/relators/ctb",
            "label":"Mitwirkung"
         },
         "agent":{
            "id":"http://d-nb.info/gnd/7741856-6",
            "label":"Kultur Ruhr GmbH",
            "type":[
               "CorporateBody"
            ]
         }
      }
   ]
}