Proceedings of the International Multiconference on Computer Science and Information Technology pp. 821–835 ISSN 1896-7094 c  2007 PIPS Modelling and Schedulability Analysis of Real-time Sequence Patterns using Time Petri Nets and Uppaal Angelo Furfaro and Libero Nigro Laboratorio di Ingegneria del Software, Dipartimento di Elettronica Informatica e Sistemistica, Universit`a della Calabria, 87036 Rende(CS) - Italy Email: a.furfaro@deis.unical.it, l.nigro@unical.it Web: http://www.lis.deis.unical.it Abstract. This paper proposes an original approach to the schedula- bility analysis of real-time systems specified by Time Petri Nets (TPNs). The focus is on sequence patterns of transition firings (execution tasks). A TPN model is first translated in the Timed Automata terms of the popular Uppaal tool. Then schedulability properties of tasks are verified through reachability analysis. The approach is efficient and scalable. The paper demonstrates the concrete application of the approach through examples. Finally, conclusions are drawn together with an indication of on-going and future work. Keywords: real-time systems, time Petri nets, timed automata, Uppaal, schedu- lability, firing sequence patterns 1 Introduction Time Petri Nets (TPNs) [16] have been proven to be a very convenient tool for specifying timing constraints in time-dependent systems [6, 22, 10]. TPNs as- sociate time pairs with transitions instead of a single delay as in timed Petri nets [18], thus TPNs are more general than timed Petri nets [4]. TPNs support formal analysis through an adaptation [4, 6] of the well-known reachability anal- ysis technique of Petri nets [17]. A reachability graph represents the complete dynamic behaviour of a TPN based on the interleaving semantics. Each node of the graph is a state class. Edges are labelled by transition firings. A state class holds a marking and a firing domain reflecting timing constraints about when the state class is possibly reached in the time domain. Examples of con- crete tools permitting the enumeration of the state classes of TPNs and enabling reachability analysis are Tina [5, 20] and Romeo [12, 19]. As pointed out in [22], although schedulability is closely related to reachabil- ity, it has more specific concerns with transition sequences rather than markings or states. In particular, an end-to-end delay of a task execution, that is an im- portant issue in time critical systems, cannot directly be derived from firing domains and state classes. 821