In this paper we introduce the concept of a Petri net component and show how systems can be composed from components. A component communicates with its environment via distinguished input and output places, which formalizes communication by message passing. Then, we present a compositional semantics for components. The semantics is an extension of processes for place/transition systems (partial order semantics). We show that the semantics is fully abstract with respect to the behaviour of closed components (essentially, processes of place/transition systems). A main feature of the compositional semantics is that composition of components corresponds to conjunction. The semantics can be easily combined with a temporal logic interpreted on processes of a place/transition system. We introduce such a logic and show how it can be combined with the semantics to achieve a rely-guarantee concept. Keywords: Petri net component, compositional semantics, rely-guarantee specification, partial ord...

. In this paper, we present two logics that allow for specifying distributed information systems, emphasizing communication among sites. The low-level logic D 0 offers features that are easy to implement but awkward to use for specification, while the high-level logic D 1 offers convenient specification features that are not easy to implement. We show that D 1 specifications may be automatically translated to D 0 in a sound and complete way. In order to prove soundness and completeness, we define our translation as a simple map of institutions. Our result may be useful for making implementation platforms like Corba easier accessible by providing high-level planning and specification methods for communication. 1 Introduction Two logics are presented that allow for specifying distributed information systems, emphasizing communication among sites. The low-level logic D 0 offers features that are easy to implement but awkward to use for specification, while the high-level logic D 1 offers...

From an arbitrary temporal logic institution we show how to set up the corresponding institution of objects. The main properties of the resulting institution are studied and used in establishing a categorial, denotational semantics of several basic constructs of object specification, namely aggregation (parallel composition), interconnection, abstraction (interfacing) and monotonic specialization. A duality is established between the category of theories and the category of objects, as a corollary of the Galois correspondence between these concrete categories. The special case of linear temporal logic is analysed in detail in order to show that categorial products do reflect interleaving and reducts may lead to internal nondeterminism. Key words: object-orientation, system specification, temporal logic, institution, denotational semantics, duality. 1 Introduction The advantages of object-orientation in software engineering in general and system specification in particular...

. The classification of properties of concurrent programs into safety and liveness was first proposed by Lamport [20]. Since then several characterizations of hierarchies of properties have been given, see e.g. [4, 18, 8, 19]; this includes syntactic characterizations (in terms classes of formulas of logics such as the linear temporal logic) as well as extensional (as sets of computations in some abstract domain). The latter often admits a topological characterization with respect to the natural topologies of the domain of computations. We introduce a general notion of a linear time model of computation which consists of partial and completed computations satisfying certain axioms. The model is endowed with a natural topology. We show that the usual topologies on strings, Mazurkiewicz traces and pomsets arise as special cases. We then introduce a hierarchy of properties including safety, liveness, guarantee, response and persistence properties, and show that our definition ...