I. Introduction and Motivation
Despite all effort that went into the development of requirements modeling languages, the vast majority of requirements specifications created today are still written in natural language, augmented with tables, pictures, and, increasingly, some model diagrams. This situation is not just due to the inability of industry to adopt modeling technology. It is a strong indicator that heavyweight modeling languages such as UML don't fit the needs of industrial requirements engineers [1]. Moreover, requirements at an early stage are by their very nature mainly narrative and pictorial.