Usable, Useful, Desirable
I've been thinking that different kinds of artifacts have different ratios of usability, usefulness, and desirability. It'd be nice to express this at the beginning of a project to set everyone's expectations and syncronize design approaches. But how to express it?
Perhaps by analogy?
Usefulness seems like a contextual and subjective quality, not a quality of the artifact itself. I could imagine owning two very different coffee makers and each would be more useful depending on the situation. A percolator is the best choice when you're camping.
Ultimately usability and desirability are relative too. For example, my sister-in-law loves the coffee from her percolator. As usual, it's important to know who you're designing for.
Same idea, in PDF format.