make CBV spec on MeasurementType more precise; add descriptions to RDF

[VladimirAlexiev]

1. special @vocab for some JSONLD props #265 (comment) describes some discrepancies between EPCIS and CBV that make me and @shalikasingh wonder whether this allows 1. MeasurementTypes, 2. SensorTypes, and/or also 3. User types (values). @RalphTro @CraigRe Please precise these texts

2. The CBV table 7.6.3 includes detailed Definition. @mgh128 I'm sure you plan to include it in the gs1 RDF?

3. Same table has "SI Unit": do you plan to match that to Rec20 and and emit it?

4. The table needs to be revised in view of @mgh128's sync to QUDT. Note: there are some misspellings in col "SI Unit": "siemen" -> "siemens"

Mark, what RDF form do you plan to use? Something like this?

@prefix quantitykind: <http://qudt.org/vocab/quantitykind/> .
@prefix qudt: <http://qudt.org/schema/qudt/> .

gs1:MeasurementType a rdfs:Class, owl:Class;
  rdfs:label "Measurement Type"@en;
  rdfs:comment "TODO";
  skos:exactMatch qudt:QuantityKind.

gs1:canonicalSIunit a rdf:Property, owl:DatatypeProperty;
  rdfs:label "canonical SI unit";
  rdfs:comment "Canonical SI unit of the measurement type, expressed as a UNECE/UNCEFACT Recommendation 20 code"@en;
  rdfs:domain gs1:MeasurementType;
  rdfs:range xsd:string.

gs1:MT-Length a gs1:MeasurementType;
  rdfs:label "Length"@en;
  rdfs:comment "The linear magnitude of any thing, as measured end to end."@en;
  gs1:canonicalSIunit "MTR";
  skos:exactMatch quantitykind:Length.

[mgh128]

1. Yes, the intention is that "type" within epcis:SensorReport can take a value from the proposed gs1:MeasurementType or gs1:SensorAlertType code lists as well as a Web URI for a user-defined / vendor-defined value if none of the standard values are appropriate.
2. Yes, we plan to include those definitions from CBV table 7.6.3 in the RDF for the GS1 Web vocabulary update - we already have that in JSON-LD in the preview site at https://milecastle.media/dev2021/voc_epcis_extras/MeasurementType
3. Yes, it's a good idea to include gs1:canonicalSIunit, aligned with Rec20.
4. @CraigRe can take care of updating table 7.6.3 in CBV.

Those are useful additions to the RDF/JSON-LD we currently have for the preview site, so I'll make an update accordingly.