On the role of ambiguity in RE

[Context and motivation] Ambiguity has long been pictured as one of the worst enemies of the specifier, especially with reference to ambiguity in natural language (NL) requirements specifications. [Question/problem] In this paper, we investigate the nature of ambiguity, and [Principal ideas/result] advocate that the sirnplistic view of ambiguity as merely a "defect" that has to be avoided at all costs does not do justice to the complexity of this phenomenon. We also provide a finer classification of several types of ambiguities, distinguishing their different causes and effects in the development process. [Contribution] This better understanding can help in the analysis of practical experiences and in the design of more effective methods to detect, mark and handle ambiguity