As part of a discussion thread on XBRL-Public, I learned something which I sort of knew but never really heard this articulation or explanation of semantic models before. It seems to make things clearer for me.
Wikipedia defines semantic models as:
Terms such as "semantic network" and "semantic data model" are used to describe particular types of data models characterized by the use of directed graphs in which the vertices denote concepts or entities in the world, and the arcs denote relationships between them.
That describes what XBRL does.
If you work with XBRL and you don't understand graph theory, you need to study up if you REALLY want to understand XBRL.