Consider:

When is the exam?
The exam is Thursday.
The exam is next week.

I know sticklers for exactitude might object to these expressions,
preferring 'when will the exam take place' or some such, but these are in
very broad use. The question, especially, sounds very natural to me.

Some might say 'Thursday' and 'next week' aren't adverbs, and that's true,
but they are _adverbials_ -- in other words, they are performing an
adverbial function. Noun phrases can do this in English. Certainly, it
would be incorrect to interpret the above expressions as containing
noun-phrase subject complements. I.e.,They aren't statements equating
'the exam' with 'Thursday' or 'next week'.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Johanna Rubba   Assistant Professor, Linguistics              ~
English Department, California Polytechnic State University   ~
San Luis Obispo, CA 93407                                     ~
Tel. (805)-756-2184     Fax: (805)-756-6374                   ~
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Office hours Winter 1999: Mon/Wed 10:10-11am Thurs 2:10-3pm   ~
Home page: http://www.calpoly.edu/~jrubba                     ~
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