Search

Inspired by P systems initiated by Gheorghe Paun, we study a computation model over a multiset of communicating objects. The objects in our model are instances of finite automata. They interact with each other by firing external transitions between two objects. Our model, called a service automaton, is intended to specify, at a high level, a service provided on top of network devices abstracted as communicating objects. We formalize the concept of processes, running over a multiset of objects, of a service automaton and study the computing power of both single-process and multiprocess service automata. In particular, in the multiprocess case, regular maximal parallelism is defined for inter-process synchronization. It turns out that single-process service automata are equivalent to vector addition systems and hence can define nonregular processes. Among other results, we also show that Presburger reachability problem for single-process service automata is decidable, while it becomes undecidable in the multiprocess case. Hence, multiprocess service automata can not be effectively simulated by vector addition systems.

Targeting at modeling the high-level dynamics of pervasive computing systems, we introduce bond computing systems (BCS) consisting of objects, bonds and rules. Objects are typed but addressless representations of physical or logical (computing and communicating) entities. Bonds are typed multisets of objects. In a BCS, a configuration is specified by a multiset of bonds, called a collection. Rules specify how a collection evolves to a new one. A BCS is a variation of a P system introduced by Gheorghe Paun where, roughly, there is no maximal parallelism but with typed and unbounded number of membranes, and hence, our model is also biologically inspired. In this paper, we focus on regular bond computing systems (RBCS), where bond types are regular, and study their computation power and verification problems. Among other results, we show that the computing power of RBCS lies between linearly bounded automata (LBA) and LBC (a form of bounded multicounter machines) and hence, the regular bond-type reachability problem (given an RBCS, whether there is some initial collection that can reach some collection containing a bond of a given regular type) is undecidable. We also study a restricted model (namely, B-boundedness) of RBCS where the reachability problem becomes decidable.