generalized RDF comment from David Booth

I would hope that David would be satisfied with a change like:

A generalized RDF triple is an RDF triple except that subjects, predicates,
and objects are all allowed to be IRIs, blank nodes, or literals. A generalized
RDF graph is an RDF graph except that the triples in it are generalized RDF
triples. A generalized RDF dataset is an RDF dataset except that the graphs
in it are generalized RDF graphs and the graph labels are IRIs, blank
nodes, or literals.

This is by no means deathless prose, but any attempt to add literary muscle
("can be", "its", ...) ends up being harder to grok.

I oppose moving this section from Concepts to Semantics.

peter