confusion over docs of Graph Groups

[TallTed]

Originally posted by @mhoangvslev in openlink/virtuoso-opensource#1277 (comment)

When I read this line from the doc, I feel confused:

Bit 8 allows to obtain list of members of graph group; an IRI can be used as graph IRI and as graph group IRI at the same time so bit 8 can be freely combined with any of bits 1, 2 or 4.

My understanding from the doc for RDF Graph Groups is that its sole purpose is to provide a convenient way to query specific subset of graphs, as described here:

It would be nice to create named lists of graphs and a clause like "SELECT from all graph names of the specified list". "Graph groups" serve for this purpose. That is Virtuoso-specific SPARQL extension that let create a named list of IRIs such that if name of the list is used in FROM clause like IRI of default graph then it is equivalent to list of FROM clauses, one clause for each item of the list.

I think the line DB.DBA.RDF_GRAPH_USER_PERMS_SET (graph_group_iri, 'nobody', 9) should be added to the DB.DBA.RDF_GRAPH_GROUP_CREATE procedure. If not possible, for security reason, it should be mentioned in the document.