You NEED both. (that's the simple version), but my experience is that
w/o the prototype there is too much ambiguity and to pull from one of
the messages of Alan's article, unpredictability.
In that other thread on SIGIA-L we were discussing how to make Axure
or any other prototyping:documentation tool better and in my mind the
ideal tool heads in the direction where interactive (behavioral)
prototypes intertwine with annotations and data binding schemas.
The discussion then focused on the need for annotations and I stressed
quite strongly that a prototype without annotations is not valuable
I may not be meeting you all the way here, but I'm not as far away as
my original strong statements that you (respectfully) disagreed with