scholarly journals Bisimulation from Open Maps

1994 ◽  
Vol 1 (7) ◽  
Author(s):  
André Joyal ◽  
Mogens Nielsen ◽  
Glynn Winskel
Keyword(s):  
Petri Nets ◽  
Parallel Computation ◽  
Transition Systems ◽  
New Model ◽  
Event Structures ◽  
Uniform Definition ◽  
Refinement Operators ◽  
Definition Of ◽  
Open Maps

An abstract definition of bisimulation is presented. It enables a uniform definition of bisimulation across a range of different models for parallel computation presented as categories. As examples, transition systems, synchronisation trees, transition systems with independence (an abstraction from Petri nets) and labelled event structures are considered. On transition systems the abstract definition readily specialises to Milner's strong bisimulation. On event structures it explains and leads to a revision of history-preserving bisimulation of Rabinovitch and Traktenbrot, Goltz and van Glabeek. A tie-up with open maps in a (pre)topos, as they appear in the work of Joyal and Moerdijk, brings to light a promising new model, presheaves on categories of pomsets, into which the usual category of labelled event structures embeds fully and faithfully. As an indication of its promise, this new presheaf model has ``refinement'' operators, though further work is required to justify their appropriateness and understand their relation to previous attempts. The general approach yields a logic, generalising Hennessy-Milner logic, which is characteristic for the generalised notion of bisimulation.

scholarly journals Models for Concurrency

1994 ◽  
Vol 1 (12) ◽  
Author(s):  
Glynn Winskel ◽  
Mogens Nielsen
Keyword(s):  
Petri Nets ◽  
Parallel Computation ◽  
Category Theory ◽  
Parallel Composition ◽  
Transition Systems ◽  
Basic Category ◽  
Event Structures ◽  
Causal Independence ◽  
Use Category ◽  
Mazurkiewicz Traces

This report surveys a range of models for parallel computation to include interleaving models like transition systems, synchronisation trees and languages (often called Hoare traces in this context), and models like Petri nets, asynchronous transition systems, event structures, pomsets and Mazurkiewicz traces where concurrency is represented more explicitly by a form of causal independence. The presentation is unified by casting the models in a category-theoretic framework. One aim is to use category theory to provide abstract characterisations of constructions like parallel composition valid throughout a range of different models and to provide formal means for translating between different models.<br /> <br />A knowledge of basic category theory is assumed, up to an acquaintance with the notion of adjunction.

scholarly journals Open Maps (at) Work

1995 ◽  
Vol 2 (23) ◽  
Author(s):  
Allan Cheng ◽  
Mogens Nielsen
Keyword(s):  
Petri Nets ◽  
Parallel Computation ◽  
Functional Languages ◽  
Process Algebras ◽  
Representative Selection ◽  
Definition Of ◽  
Testing Equivalence ◽  
Selection Of ◽  
Open Maps

The notion of bisimilarity, as defined by Park and Milner,<br />has turned out to be one of the most fundamental notions of operational<br />equivalences in the field of process algebras. Not only does it induce<br />a congruence (largest bisimulation) in CCS which has nice equational<br />properties, it has also proven itself applicable for numerous models of<br />parallel computation and settings such as Petri Nets and semantics of<br />functional languages. In an attempt to understand the relationships and<br />differences between the extensive amount of research within the field,<br />Joyal, Nielsen, and Winskel recently presented an abstract category-theoretic <br />definition of bisimulation. They identify spans of morphisms satisfying certain "path lifting"<br /> properties, so-called open maps, as a possible abstract definition of bisimilarity.<br /> In [JNW93] they show, that they can capture Park and Milner's bisimulation. <br />The aim of this paper is to show that the abstract definition of bisimilarity is applicable<br />"in practice" by showing how a representative selection of well-known<br />bisimulations and equivalences, such as e.g. Hennessy's testing equivalence,<br />Milner and Sangiorgi's barbed bisimulation, and Larsen and Skou's<br />probabilistic bisimulation, are captured in the setting of open maps and<br />hence, that the proposed notion of open maps seems successful. Hence,<br />we confirm that the treatment of strong bisimulation in [JNW93] is not<br />a one-off application of open maps.

scholarly journals Presheaf Models for CCS-like Languages

1999 ◽  
Vol 6 (36) ◽  
Author(s):  
Gian Luca Cattani ◽  
Glynn Winskel
Keyword(s):  
General Definition ◽  
General Process ◽  
Process Calculi ◽  
Event Structures ◽  
Open Map ◽  
Process Operations ◽  
Definition Of ◽  
Refinement Operator ◽  
Congruence Properties ◽  
Open Maps

The aim of this paper is to harness the mathematical machinery around<br />presheaves for the purposes of process calculi. Joyal, Nielsen and Winskel<br />proposed a general definition of bisimulation from open maps. Here we show<br />that open-map bisimulations within a range of presheaf models are congruences<br /> for a general process language, in which CCS and related languages<br />are easily encoded. The results are then transferred to traditional models<br /> for processes. By first establishing the congruence results for presheaf<br />models, abstract, general proofs of congruence properties can be provided<br />and the awkwardness caused through traditional models not always possessing<br /> the cartesian liftings, used in the break-down of process operations,<br />are side-stepped. The abstract results are applied to show that hereditary<br />history-preserving bisimulation is a congruence for CCS-like languages to<br />which is added a refinement operator on event structures as proposed by<br />van Glabbeek and Goltz.

Event Structure Representation of the Behaviour of Place/Transition Systems

1988 ◽  
Vol 11 (4) ◽  
pp. 405-432
Author(s):  
Józef Winkowski
Keyword(s):  
Petri Nets ◽  
Event Structure ◽  
Transition Systems ◽  
Structure Representation ◽  
Global Behaviour ◽  
Event Structures ◽  
Mathematical Systems

It is shown how the nonsequential behaviour of marked Petri nets of places and transitions can be described with the aid of mathematical systems related to labelled event structures. The method of description is modular in the sense that the global behaviour is obtained by combining local ones corresponding lo places and transitions.

Development and Evaluation of Fuzzy Criteria for the Diagnosis of Rheumatoid Arthritis

1996 ◽  
Vol 35 (04/05) ◽  
pp. 334-342 ◽  
Author(s):  
K.-P. Adlassnig ◽  
G. Kolarz ◽  
H. Leitich
Keyword(s):  
Rheumatoid Arthritis ◽  
Reference Model ◽  
American Rheumatism Association ◽  
Uniform Definition ◽  
Sensitivity Rate ◽  
Fuzzy Techniques ◽  
Definition Of ◽  
Different Levels ◽  
Specificity Rate

Abstract:In 1987, the American Rheumatism Association issued a set of criteria for the classification of rheumatoid arthritis (RA) to provide a uniform definition of RA patients. Fuzzy set theory and fuzzy logic were used to transform this set of criteria into a diagnostic tool that offers diagnoses at different levels of confidence: a definite level, which was consistent with the original criteria definition, as well as several possible and superdefinite levels. Two fuzzy models and a reference model which provided results at a definite level only were applied to 292 clinical cases from a hospital for rheumatic diseases. At the definite level, all models yielded a sensitivity rate of 72.6% and a specificity rate of 87.0%. Sensitivity and specificity rates at the possible levels ranged from 73.3% to 85.6% and from 83.6% to 87.0%. At the superdefinite levels, sensitivity rates ranged from 39.0% to 63.7% and specificity rates from 90.4% to 95.2%. Fuzzy techniques were helpful to add flexibility to preexisting diagnostic criteria in order to obtain diagnoses at the desired level of confidence.

scholarly journals Transition-Systems, Event Structures, and Unfoldings

1995 ◽  
Vol 118 (2) ◽  
pp. 191-207 ◽  
Author(s):  
M. Nielsen ◽  
G. Rozenberg ◽  
P.S. Thiagarajan
Keyword(s):  
Transition Systems ◽  
Event Structures

scholarly journals “There must be Someone’s Name Under Every Bit of Text, Even if it is Unimportant or Incorrect”: Plagiarism as a Learning Strategy

2021 ◽  
Author(s):  
Beata Bielska ◽  
Mateusz Rutkowski
Keyword(s):  
Higher Education ◽  
Detection Rate ◽  
Learning Strategy ◽  
Plagiarism Detection ◽  
International Context ◽  
Detection Systems ◽  
Uniform Definition ◽  
Definition Of ◽  
Difficult Situations ◽  
Source Of Information

AbstractThe article offers analyses of the phenomenon of copying (plagiarism) in higher education. The analyses were based on a quantitative survey using questionnaires, conducted in 2019 at one of the Polish universities. Plagiarism is discussed here both as an element of the learning process and a subject of public practices. The article presents students’ definitions of plagiarism, their strategies for unclear or difficult situations, their experiences with plagiarism and their opinions on how serious and widespread this phenomenon is. Focusing on the non-plagiarism norm, that is the rule that students are not allowed to plagiarize, and in order to redefine it we have determined two strategies adopted by students. The first is withdrawing in fear of making a mistake (omitting the norm), which means not using referencing in unclear situations, e.g. when the data about the source of information are absent. The second is reducing the scope of the norm applicability (limiting the norm), characterized by the fact that there are areas where the non-plagiarism norm must be observed more closely and those where it is not so important, e.g. respondents classify works as credit-level and diploma-level texts, as in the credit-level work they “can” sometimes plagiarize since the detection rate is poor and consequences are not severe. The presented results are particularly significant for interpreting plagiarism in an international context (no uniform definition of plagiarism) and for policies aimed at limiting the scale of the phenomenon (plagiarism detection systems1).

A Compositional Semantics for Timed Petri Nets1

1990 ◽  
Vol 13 (2) ◽  
pp. 141-170
Author(s):  
Andrea Maggiolo-Schettini ◽  
Józef Winkowski
Keyword(s):  
Petri Nets ◽  
Compositional Semantics ◽  
Timed Petri Nets ◽  
Event Structures ◽  
Configuration Systems

Timed Petri nets and their behaviours are considered. A concept of a seminet is introduced. which generalizes the concept of a net, and suitable operations on seminets are defined, which allow constructing seminets from atoms corresponding to places and transitions. The behaviours of seminets are given in the form of so called configuration systems, a notion close to labelled event structures. Such behaviours can be combined with the aid of operations corresponding to those on seminets. In particular, the behaviour of a compound seminet can be obtained by combining the behaviours of components.

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