System quality is assessed with respect to the value of relevant properties of that system. The level of abstraction of these properties can be very high (e.g. usability) or very low (e.g. all the “Ok” buttons in the application have the same size). These properties can be generic and thus applicable to a large group of systems (e.g. all the interactive systems should be usable) or very specific to a system (e.g. the “Quit” button in my application should always be visible). While properties identification and verification is at the core of interactive systems engineering, much less attention is paid to properties that aims at characterizing a pair (or more) of systems. In this paper, we propose to study such properties (defined as across-systems properties) and propose a notation for representing them. We propose a process for the analysis of such properties using the proposed notation. This process and analysis can be used during systems design or integration. We also present several examples of across-systems properties and demonstrate their importance and use on a simple example of aircraft cockpits buttons.