In revising my own list of basic sentence patterns, I am ready to join
Martha Kolln and others in seeing  subject+BE+adverb of time* or place as
a pattern:

John is here.
John is in the kitchen.


Would I be drummed out of the profession if I called that adverb a
complement because it completes its verb  as much as  subject complements
or direct objects complete their verbs?

MIchael Kischner

*Actually, I can't think of an adverb of time that goes comfortably in
that slot.  "Choir practice is on Thursdays" doesn't seem to cut it; in
that sentence, BE seems to be just a shortcut for HAPPEN or OCCUR.  I know
that something similar is said of BE with an adverb of place -- that BE
then means EXIST.  But this isn't my main question.