Due to the multi-disciplinary nature of AoIR we've generally encouraged people to follow their own discipline's general guidelines. For example, in communication this would mean about 25-30 double spaced pages of text max (plus references, etc.). However, from past years I know that some disciplines don't even expect full-length papers at the time of the conference. As a matter of fact, I remember some people being upset because another person only had presentation notes and not a full-length paper, while that person was upset that someone would demand a full paper at that point... Obviously it would be preferable if you had a paper, not just notes, because that way it can be shared with others. However, as I said above, try to do the best work possible according to your discipline's guidelines. As to length of papers for the annual - I don't know. Ulla