Considering Architectural Properties in Real-time Play-out

Abstract

Real-time embedded systems (RTES), as in the automotive domain, provide their functionality by executing software operations on hardware with restricted resources and by communicating via buses. The properties of the underlying architecture, i.e., execution times of software operations and bus latencies, cause delays during the provision of the functionality. At the same time, RTES have to fulfill strict real-time requirements. The fulfillment of such real-time requirements under consideration of delays induced by architectural properties should be taken into account already during requirements engineering (RE) to avoid costly iterations in subsequent development phases. In previous work, we developed a formal RE approach based on a recent Live Sequence Chart (LSC) variant, so-called Modal Sequence Diagrams (MSDs). This scenario-based RE approach allows to validate the requirements by means of simulation, i.e., the play-out algorithm originally conceived for LSCs. Our MSD play-out approach considers assumptions on the environment as well as real-time requirements and is applicable to hierarchical component architectures, which makes it well suited for automotive systems. However, delays induced by architectural properties are not considered. In order to consider this important aspect, we introduce in this paper an approach enabling the annotation of software operation execution times and connector latencies to hierarchical component architectures by means of the MARTE profile. These assumptions about the architectural properties can be verified against the realtime requirements specified in the MSDs by means of simulation. We illustrate the approach by means of an example of an automotive RTES.