Models in the RE seriesre@21

This paper reports on the use and importance of models in the RE (Requirements Engineering) series of conferences based on the results of an analysis of the use of the word `model´ and of other words with `model...´ as their stem in the main bodies of the texts of published papers. The 620 papers examined contained 18,066 instances of these words. The words identified were divided into `general terms´ for models (505), `special names´ for models (215) and names for the `nature and characteristics´ of models and modelling (120). The large numbers are a clear indicator of the overall importance which the model has as a dominant concept and as a still proliferating artifact in the practice of those participating in the series. The three groups of names represent social conventions adopted for communication and continuity; the third provides a pragmatically rather than theoretically based overview of the factors affecting models and modelling. The conclusions suggest questions that may improve general practice and form the basis of more specific model declaration.