Pursuant to our discussion this morning about the new version of help.unc.edu, I decided to revisit Flamenco. I'm pretty sure I've rambled on about that project before, but if not, well there it is. It's an interesting search interface that does many things well, I think. I read through one of their publications (pdf) and a few things jumped out at me:

• Searching can be categorized as being either directed or open-ended. One type of user is looking for a very specific answer; once they've found it, they'll know they've found it and that's the end of their search. It's easy to measure success in this sort of scenario. Either they found the answer or they didn't. The open-ended search is a bit more difficult to evaluate. As long as they find something then the search has some measure of success.
• Users performing a directed search aren't interested in advanced search options. All they want is a search box that they can type words into and get results back.
• Clicking on links to navigate through a collection is more intuitive than entering words into forms.