Specifying Real-Time Requirements for SDL Specifications — A Temporal Logic-Based Approach

Abstract

The expressiveness of many state-transition based formal description techniques, e.g. the ITU-TS standardised Specification and Description Language (SDL), does not capture hard real-time requirements. In telecommunications systems engineering, hard real-time requirements, however, are an important class of properties. They occur in the description of progress properties in telecommunications protocols as well as in the specification of real-time related of Quality of Service (QoS) requirements. We suggest integrating functional system properties, given as SDL specifications, with real-time requirements expressed in terms of real-time temporal logic formulas. We call the resulting specifications ‘complementary specifications’. First, we show the inexpressiveness of SDL with respect to hard real-time requirements. Next, we define a common model theoretic foundation which allows SDL specifications to be used jointly with temporal logic specifications. Then we give examples of commonly used real-time related QoS requirements, namely delay bound, delay jitter, and isochronicity. We also discuss the specification of various QoS mechanisms, like QoS negotiation, QoS monitoring and jitter compensation. Finally, we point at related formal verification problems.