Aligning Kerameikos.org more directly with CIDOC-CRM

When the Kerameikos.org project was founded in 2013, our intent was for the LOD thesaurus system to be modeled primarily in SKOS, with instances in certain categories to be designated subject-specific RDF classes in our own ontology (e.g., kon:Shape) or classes in existing ontologies (for example, foaf:Person and foaf:Group).

Our thesaurus is still built around SKOS, but since we have aligned our vase aggregation RDF model with Linked Art (a community-built CIDOC-CRM profile serialized as JSON-LD), I have subsequently made some alterations to the classes we use for concept URIs and updated our ontology.

These changes affect the RDF concepts themselves, but also I've searched and replaced classes throughout the Kerameikos codebase as well.

• foaf:Person has been replaced with crm:E21_Person
• foaf:Group has been replaced with crm:E74_Group
• kon:ProductionPlace has been replaced with crm:E53_Place and kon:ProductionPlace has been deprecated from the Kerameikos ontology.
• Spatial expressions are dually compatible with both CIDOC-CRM and the WGS84 ontology in that the E53:Place concept includes both geo:location and crm:P168_place_is_defined_by properties linking to the same node URI, which carries both the geo:SpatialThing and crmgeo:SP5_Geometric_Place_Expression classes. These spatial features may include geo:lat and geo:long (for points) or osgeo:asGeoJSON as before, but now include the crmgeo:asWKT property with a datatype of http://www.opengis.net/ont/geosparql#wktLiteral, which should make these points and polygons compatible with endpoints that support the GeoSPARQL protocol. See the machine-readable data underlying http://kerameikos.org/id/athens, for example.
  

The Kerameikos.org ontology page has been significantly revised to make it more transparent than before, in line with improvements we have made to the Nomisma page in recent years. The ontology URI now supports content negotiation to request RDF/XML or Turtle as alternatives with the Accept header and relevant mime-types. We have also implemented ontology versions, so that you can compare the 2015 edition with the current 2021 revision.

The ontology has been tightened up with better definitions of our few custom ceramic-oriented RDF classes (Shape, Technique, and Style), all of which are subclasses of crm:E55_Type. There is one property, kon:hasShape, which is a subproperty of crm:P2_has_type, intended to link a Human-Made Object (vase) [rdfs:domain] to the range [rdfs:range] of kon:Shape. Therefore, this expression is fully compatible with CIDOC-CRM's own domains and ranges while also conforming to the standard intellectual vocabulary of pottery specialists. We may implement a "Fabric" class as a subclass of crm:E37_Material in order to make technical distinctions between the clay from Corinth and Attica, for example. We will expand the scope of our ontology, and its relationship to CIDOC-CRM, as use cases arise.