A variety of user interface development methodologies have been described over the last twenty years. Yet it is often difficult to understand exactly how to follow a methodology, to understand how one methodology differs from another, or how to combine two methodologies. This paper shows how methodologies can be characterized by applying a formal analysis technique, developed originally for examining software development methodologies. The technique is illustrated by applying it to the Shneiderman user interface development methodology. As a result of the examination, a number of improvements to the Shneiderman methodology are suggested.