I say this was a difficult question, because as anyone familiar with the field knows, many people have widely varying answers! There has always been intense debate among IA / user experience practitioners as to who we are and conceptually what we really do. I gave an answer that indicated my familiarity with recent conversations in this regard (notably from the 2009 IA Summit), and muttered some standard words that probably conformed roughly to some textbook definitions of what IA is all about. That seemed to satisfy the people interviewing me that I knew what I was about.