RDF elements descriptions

[zvr]

Feedback from OMG:

5. Every element in your ontology should be declared and have, at a minimum, an rdfs:label and skos:definition. That would require adding the namespace for SKOS (Simple Knowledge Organization System, which is a W3C recommendation) to the header of your file, and then using skos:definition throughout rather than rdfs:comment. Definitions should be expressed using ISO 704 style, which is an expression that does not start with an upper case letter (unless the word is a proper noun), does not end in punctuation, and is not a full sentence. It should be something you can use to replace the name of the concept/class in a sentence. Any other details should be in skos:note, or similar annotation. We define a number of useful annotations in the Commons Annotation Vocabulary at the URI given in 4. You might consider importing it if any of them are useful to you. Certainly for the copyright statement you should consider doing so.