A proposal to be discussed is about the use of dct:conformsTo to specify spatial and temporal reference systems, and to represent them as skos:Concept's, as per the following examples:

• If an HTTP URI is used:

   <dct:conformsTo rdf:resource="http://www.opengis.net/def/crs/EPSG/0/27700"/>

• If an URN is used:

    <dct:conformsTo>
      <skos:Concept>
        <dct:identifier rdf:datatype="http://www.w3.org/2001/XMLSchema#anyURI">urn:ogc:def:crs:EPSG::27700</dct:identifier>
      </skos:Concept>
    </dct:conformsTo>

• In all the other cases:

    <dct:conformsTo>
      <skos:Concept>
        <skos:prefLabel xml:lang="en">OSGB 1936 / British National Grid (EPSG:27700)</skos:prefLabel>
        <owl:versionInfo xml:lang="en">7.4</owl:versionInfo>
       <skos:inScheme>
          <skos:ConceptScheme>
            <rdfs:label xml:lang="en">EPSG</rdfs:label>
          </skos:ConceptScheme>
        </skos:inScheme>
     </skos:Concept>
    </dct:conformsTo>

GeoDCAT-AP Draft 7 includes the following syntax bindings:

• spatial resolution §6.2: spatial resolution is represented in a human-readable form only, using property rdfs:comment.
• coordinate reference system §13: using dct:conformsTo and corresponding URIs from the “EPSG coordinate reference systems” register operated by the Open Geospatial Consortium, in combination with an additional statement with predicate dct:type, with the following code list value defining the notion of spatial reference system: http://inspire.ec.europa.eu/glossary/SpatialReferenceSystem.
• temporal reference system  §13: using dct:conformsTo in combination with an additional statement with predicate dct:type, with the following code list value defining the notion of temporal reference system: http://inspire.ec.europa.eu/glossary/TemporalReferenceSystem.

# Spatial resolution as equivalent scale

[]  a dcat:Dataset ;

    rdfs:comment "Spatial resolution (equivalent scale): 1:10000"@en .

# Spatial resolution as distance

[]  a dcat:Dataset ;

    rdfs:comment "Spatial resolution (distance): 5 km"@en .

# Coordinate reference system

[]  a dcat:Dataset ;

    dct:conformsTo <http://www.opengis.net/def/crs/EPSG/0/4258> .

<http://www.opengis.net/def/crs/EPSG/0/4258>

    dct:type <http://inspire.ec.europa.eu/glossary/SpatialReferenceSystem> .

See also e-mail by Stefan Kafka:

http://joinup.ec.europa.eu/mailman/archives/dcat_application_profile-geo/2015-December/000313.html

"Hi all,

hmm, I don't like the scale / resolution coding in the current version.  Is
it some possibility to code it more structured than 

<rdfs:comment xml:lang="en">Spatial resolution (equivalent scale):
XXXXX</rdfs:comment> ?

I have found e.g. http://bibframe.org/vocab/Cartography.html where scale is
defined. Also http://dbpedia.org/ontology/scale exists.

What do you think about it?

Stepan Kafka"

https://www.researchgate.net/publication/262936829_A_geologic_timescale… provides information on an RDF approach to modelling ISO 19108 but I am not sure of the status or adoption of this work.

Use / application profile of ISO 8601 is available from http://www.epimorphics.com/web/wiki/using-interval-set-uris-statistical… and also  http://id.loc.gov/datatypes/edtf/EDTF-level0.html .  The first of these is used in UK Gov and Scottish Gov RDF data cubes.