Beverly Serrel's book, "Exhibit Labels: An Interpretive Approach," has a
chapter on labels that ask questions.  I would strongly urge anyone involved
in exhibit interpretation to read it -- not just the chapter, the entire
book.

Anyway, her points (as I understand them) are:

1)      Yes, it's fine to ask questions in labels, provided

2)      You answer them immediately (even if the answer is "we don't know"
or "experts differ"), and

3)      MOST IMPORTANT -- you ask questions that the visitors themselves
would ask.  Otherwise, the visitor may legitimately answer your question by
saying "I don't care" and move on, not reading the label.

Eugene Dillenburg
Lead Developer, Philippine Coral Reef Exhibit
John G. Shedd Aquarium
1200 S. Lake Shore Drive
Chicago, Ill.  60605

V) 312 / 692-3136
F) 312 / 939 - 8001
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"Rules of grammar which don't contribute to clarity can be thrown out with
the classroom chalk stubs." -- Heywood Hale Broun