xsd:string range excludes language-tagged strings

[cygri]

Where schema.org properties have the expected type “Text”, we express that as xsd:string. This is too narrow, because it excludes language-tagged strings, and surely a text tagged with a language is valid. The alternative, rdfs:Literal, is too broad because it includes many kinds of non-text literals.

We might want to wait until the RDF WG proposes a new datatype or class that includes both tagged and untagged strings, which is on their agenda.

(Originally pointed out by Aidan.)