Verification of Timeliness QoS Properties in Multimedia Systems

One of the main challenges of the design of object-based Distributed Multimedia Systems is to address the performance related issues such as the Quality of Service (QoS). The specification of QoS is a crucial part of architectural object-based methods such as Open Distributed Processing (ODP). In the ODP, a QoS property assigned to an object is modelled via two clauses of required and provided QoS statements, which specify the level of QoS required/provided by an object from/to its environment, respectively. An over-demanding QoS statement can be beyond the physical limitation of the system and might result in inconsistencies. In particular, to produce a correct design, it is crucial to study the effect of QoS statements of components on the overall behaviour of the system in earlier stages of the design. This paper develops a theory for the verification of Timeliness QoS properties such as Jitter, Throughput and Latency. The approach adopted is based on the idea of Test Automata. We shall present a formal definition of Timeliness QoS properties, which is used for the creation of Test Automata. Such Test Automata, which we shall refer to as QoS Timed Automata, can be used to verify the corresponding QoS Timeliness property. The method is illustrated by the verification of Throughput in a Video Player systems via the model checker UPPAAL.