March 24, 2000: Essential Use Cases (Constantine and Lockwood) are a geeky HCI way of formally defining the types of people who will use a system and how they'll do so. The key is keeping things abstract to distance yourself from specific technologies or implementations. I find these sorts of formal exercises really, really frustrating while I'm doing them, but they can be a very powerful way to break free from the implementation-lock that sets in so quickly on a project.