The difference between information retrieval and information architecture

On the IA Institute members's list, Christina Wodtke asked about the difference between information architecture and information retrieval. Margie Coles had the answer: wayfaring.

You can see similar suggestion in the shift from task-centered design to goal-directed design, and from goal-directed design to message-driven design. The ACM Ubiquity article, "Why features don't matter anymore: the new laws of digital technology", approaches the same topic. (Message is how I define the the other, oft-missing, part of the mental model.)