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Coalgebras have been proposed as formal basis for the semantics of objects in the sense of object-oriented programming. This paper shows that this semantics provides a smooth interpretation for subtyping, a central notion in object-oriented programming. We show that different characterisations of behavioural subtyping found in the literature can conveniently be expressed in coalgebraic terms. We also investigate the subtle difference between behavioural subtyping and refinement.
Coalgebras have been proposed as formal basis for the semantics of
objects in the sense of object-oriented programming.
This paper shows that this semantics provides a smooth
interpretation for subtyping,
a central notion in object-oriented programming.
We show that different characterisations of
behavioural subtyping
found in the literature can conveniently be expressed in coalgebraic terms.
We also investigate the subtle difference between
behavioural subtyping and refinement.
The problem of developing a general methodology for system design has always been demanding. For this purpose, an evolutionary algorithm, adapted with design-specific representation data structures is devised. The representation modeling the system to be designed, is composed of three levels of abstraction: the first, is an 'abstract brain' layer - mainly a number of competing finite state machines, which in turn control the second level composed of fuzzy Petri nets; the third level constitutes...
Proof systems with sequents of the form
U ⊢ Φ for
proving validity of a propositional
modal μ-calculus formula Φ over a set U of
states in a given model usually handle
fixed-point formulae through unfolding, thus allowing such formulae
to reappear in a proof. Tagging is a technique originated by Winskel
for annotating fixed-point formulae with information
about the proof states at which these are unfolded. This information
is used later in the proof to avoid unnecessary unfolding, without...
In order to approximate discrete-event systems in which there exist considerable states and events, David and Alla define a continuous Petri net (CPN). So far, CPNs have been a useful tool not only for approximating discrete-event systems but also for modelling continuous processes. Due to different ways of calculating instantaneous firing speeds of transitions, various continuous Petri net models, such as the CCPN (constant speed CPN), VCPN (variable speed CPN) and the ACPN (asymptotic CPN), have...
In a recent paper by one of the authors it has been shown that there is a relationship between algebraic structures and labeled transition systems. Indeed, it has been shown that an algebraic structures can be viewed as labeled transition systems, which can also be viewed as multigraphs. In this paper, we extend this work by providing an estimation of the transition possibilities between vertices that are connected with multiarcs.
To model the dynamics of discrete deterministic systems, we extend the Petri nets framework by a priority relation between conflicting transitions, which is encoded by orienting the edges of a transition conflict graph. The aim of this paper is to gain some insight into the structure of this conflict graph and to characterize a class of suitable orientations by an analysis in the context of hypergraph theory.
More than a decade ago, Moller and Tofts published their seminal work on relating processes, which are annotated with lower time bounds, with respect to speed. Their paper has left open many questions regarding the semantic theory for the suggested bisimulation-based faster-than preorder, the MT-preorder, which have not been addressed since. The encountered difficulties concern a general compositionality result, a complete axiom system for finite processes, a convincing intuitive justification of...
More than a decade ago, Moller and Tofts published their seminal
work on relating processes, which are annotated with lower time
bounds, with respect to speed. Their paper has left open many
questions regarding the semantic theory for the suggested
bisimulation-based faster-than preorder, the MT-preorder, which
have not been addressed since. The encountered difficulties concern
a general compositionality result, a complete axiom system for
finite processes, a convincing intuitive justification...
Three basic operations on labelled net structures are proposed: synchronised union, synchronised intersection and synchronised difference. The first of them is a version of known parallel composition with synchronised actions identically labelled. The operations work analogously to the ordinary union, intersection and difference on sets. It is shown that the universe of net structures with these operations is a distributive lattice and – if infinite pre/post sets of transitions are allowed – even...
Three basic operations on labelled net
structures are proposed: synchronised union, synchronised intersection and synchronised difference. The first of them is a version of known parallel composition with synchronised actions identically labelled. The operations work analogously to the ordinary union, intersection and difference on sets.
It is shown that the universe of net structures with these operations is a distributive lattice and – if infinite pre/post sets of transitions are allowed – even...
In this paper we introduce a new modeling paradigm for developing a decision process representation called the Colored Decision Process Petri Net (CDPPN). It extends the Colored Petri Net (CPN) theoretic approach including Markov decision processes. CPNs are used for process representation taking advantage of the formal semantic and the graphical display. A Markov decision process is utilized as a tool for trajectory planning via a utility function. The main point of the CDPPN is its ability to...
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