In this paper we present the results of an evaluation applied to a set of notational elements in interactive systems. The evaluation was carried out in order to: 1. Validate the categories of an activity taxonomy for interactive systems and 2. Analyse the level of understanding that engineers and students developing interactive systems have about these elements (which can be well classified within the categories of activity taxonomy). The final purpose of this research is to define a language that is generic enough to represent the activity and serves as a basis for defining executable languages within the framework of the design of interactive systems.