Abstract
The system of communication plays a critical role in the design, management and change management of purposeful human activity systems. This occurs not only in the verbal and written form of communication but also in the assimilation and interpretation of purposeful human activity system signs. The authors propose that purposeful human activity systems exhibit four types of signs: those indicating the system's persisting meaning, behaviour, structure and process. These signs together indicate the current state of the purposeful human activity system they emerge from and form the foundations of the communication system. Currently, the connection of signs back to a communication system has been largely unexplored, and a taxonomy for identifying and delineating signs in this research context does not exist. The authors present the theoretical virtue of purposeful human activity system signs and a taxonomy developed for identifying and delineating system signs with application for novice system analysts.