Wyniki wyszukiwania - BazTech

1

Discovering Process Models with Long-Term Dependencies while Providing Guarantees and Filtering Infrequent Behavior Patterns

Mannel Lisa L, van der Aalst Wil M. P.

Fundamenta Informaticae

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2024

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Vol. 190, nr 2-4

109--158

EN

In process discovery, the goal is to find, for a given event log, the model describing the underlying process. While process models can be represented in a variety of ways, Petri nets form a theoretically well-explored description language and are therefore often used. In this paper, we extend the eST-Miner process discovery algorithm. The eST-Miner computes a set of Petri net places which are considered to be fitting with respect to a certain fraction of the behavior described by the given event log as indicated by a given noise threshold. It evaluates all possible candidate places using token-based replay. The set of replayable traces is determined for each place in isolation, i.e., these sets do not need to be consistent. This allows the algorithm to abstract from infrequent behavioral patterns occurring only in some traces. However, when combining places into a Petri net by connecting them to the corresponding uniquely labeled transitions, the resulting net can replay exactly those traces from the event log that are allowed by the combination of all inserted places. Thus, inserting places one-by-one without considering their combined effect may result in deadlocks and low fitness of the Petri net. In this paper, we explore adaptions of the eST-Miner, that aim to select a subset of places such that the resulting Petri net guarantees a definable minimal fitness while maintaining high precision with respect to the input event log. Furthermore, current place evaluation techniques tend to block the execution of infrequent activity labels. Thus, a refined place fitness metric is introduced and thoroughly investigated. In our experiments we use real and artificial event logs to evaluate and compare the impact of the various place selection strategies and place fitness evaluation metrics on the returned Petri net

2

Modeling a negotiation process between aircraft using petri nets

Żuchowska Daria, Stelmach Anna

Zeszyty Naukowe. Transport / Politechnika Śląska

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2023

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z. 121

267--285

EN

New air traffic control ideas are sought. Many studies point out the delegation of the responsibility for ensuring separation from air traffic controllers to the aircraft crews, but it should be assumed that the transition from centralized to decentralized air traffic control will occur in stages. It is, therefore, necessary to ensure effective communication between conflicting aircraft and to define the negotiation process between aircraft. The concept of the process of negotiation and communication between aircraft in conflict using a monotonic concession protocol is presented. The proposed solution was modeled using a Petri Net, which allowed us to analyze all the dependencies present in the system. The analysis allowed us to evaluate the method in the context of safety. The conducted research showed that, under the assumed conditions, the negotiation method allows obtaining the desired effect of negotiations while maintaining an adequate level of safety.

3

Towards digital twin-driven performance evaluation methodology of FMS

Bocewicz Grzegorz, Wójcik Robert, Sitek Paweł, Banaszak Zbigniew

Applied Computer Science

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2022

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Vol. 18, no 3

5--18

EN

The paper presents a method of automated modelling and performance evaluation of concurrent production flows carried out in Flexible Manufacturing Systems. The method allows for quick assessment of various variants of such systems, considering their structure and the organization of production flow of possible ways of their implementation. Its essence is the conditions imposed on the designed model, limiting the space of possible variants of the production flow only to deadlock-free variants. The practical usefulness of the model implemented in the proposed method illustrates the example, which describes the simultaneous assessment of alternative variants of the flexible machining module's structure and the planned multi-assortment production. The ability of the method to focus on feasible solutions offers attractive perspectives for guiding the Digital Twin-like scenario in situations caused by the need to change the production flow.

4

Availability analysis of an offshore oil and gas production system subjected to age-based preventive maintenance by Petri Nets

Lotovskyi Eduard, Teixeira Angelo Palos, Soares Guedes Carlos

Eksploatacja i Niezawodność

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2020

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Vol. 22, no. 4

627--637

EN

The main objective of this paper is to model an offshore oil production system subjected to age-based preventive maintenance strategies by Petri Nets and to evaluate its availability by Monte Carlo Simulation. The oil processing and the separation equipment with their reliability and maintainability characteristics, the corrective and preventive maintenance policies and the operational dependencies that lead to the reconfiguration of the system after the failure are implemented. A special attention is given to the effect of age-based perfect and imperfect preventive maintenance strategies on the system availability. The maintenance actions consider the components’ age thresholds and an age reduction ratio. Moreover, the variation of the oil and gas flows from the well over the years is accounted by the model. As case study, an offshore production installation that operates in a Brazilian oilfield is adopted. An elasticity analysis on the model parameters is conducted to assess influence of the maintenance policy on the system availability and on the oil production.

5

Causal reversibility in individual token interpretation of Petri Nets

Benamira Adel

Computer Science

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2020

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T. 21 (4)

489-511

EN

Causal reversibility in concurrent systems means that events that the origin of other events can only be undone after undoing its consequences. In opposition to backtracking, events that are independent of each other can be reversed in an arbitrary order; in other words, we have flexible reversibility with respect to a causality relationship. An implementation of individual token interpretation of Petri Nets (IPNs) has been proposed by Rob Van Glabbeek et al.; the present paper investigates a study of causal reversibility within IPNs. Given N as an IPN, by adding an intuitive firing rule to undo transitions according to the causality relationship, the coherence of N is assured; i.e., the set of all reachable states of N in the reversible version and that of the original one are identical. Furthermore, reversibility in N is flexible, and their initial state can be accessible in reverse from any state. In this paper, an approach for controlling causal-reversibility within IPNs is proposed.

6

Automatyczny system wspomagający proces projektowania systemów dyskretnych z wykorzystaniem hipergrafów

Wiśniewska M.

Pomiary Automatyka Kontrola

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2011

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R. 57, nr 7

726-728

PL

W artykule zaprezentowany został autorski system wspomagający proces projektowania systemów dyskretnych z wykorzystaniem hipergrafów. Narzędzie Hippo składa się ze zbioru bibliotek, realizujących najważniejsze operacje z zakresu teorii grafów i hipergrafów (m. in. kolorowanie, pokrycie, dopełnienie, dualizm, itd.), które zostały zrealizowane pod kątem ich zastosowania w dekompozycji systemów dyskretnych. Głównym zadaniem systemu jest usprawnienie oraz automatyzacja procesu dekompozycji systemów dyskretnych stosowanych m.in. w projektowaniu zaawansowanych układów cyfrowych (redukcja rozmiaru pamięci, selekcja klas kompatybilności, minimalizacja funkcji logicznych, dekompozycja automatów cyfrowych). Opracowany system Hippo umożliwia przeprowadzenie automatycznego procesu dekompozycji z zastosowaniem różnych algorytmów (zarówno grafowych, jak i hipergrafowych), w efekcie pozwalając wybrać użytkownikowi najkorzystniejsze rozwiązanie.

EN

In the paper a dedicated CAD system Hippo for automatic decomposition of discrete systems is presented. The tool consists of a set of libraries. Each library was designed as a separate module to solve the particular problem from the field of the graph and hypergraph theories (among others: vertex coloring, vertex covering, transversal computation, dualism, computation of the graph and hypergraph complement). The main task of the system is to improve the process of decomposition of discrete systems (for example: reduction of the microinstruction length, selection of the compatibility classes, decomposition of concurrent automata). The Hippo system consists of eight main modules:- complement -calculation of graph/hypergraph complement;- coloring - five methods of coloring of graph and hypergraph (four greedy and one backtracking);- transversal - four methods of transversals computation (fast reduction algorithm, greedy, backtracking, mixed fast reduction and greedy);- exact transversals - the calculation of the exact transversals is based on the Knuth DLX algorithm, the main advantage of such a solution is polynomial computational time in case of exact hypergraphs;- dualism (only for hypergraphs) - calculates the dual hypergraph;- converting graph to hypergraph;- converting hypergraph to graph;- conversion of the graph/hypergraph description to the TeX format.In the paper particular libraries are described in detail. Moreover, the stand-alone application (Hippo) is shown. Finally, an example of automatic decomposition of the discrete system is presented. All steps and required operations are described.

7

Tworzenie wzorców zachowań dla aplikacji opartych o architekturę EDA

Dziubich K., Dziubich T.

Metody Informatyki Stosowanej

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2008

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nr 3 (Tom 16)

85--95

EN

The following paper presents a context-aware application based on Event Driven Architecture (EDA). This application is dedicated for pervasive and ubiquitous environments. The most important problem for such applications is a process of scenario definition and behaviour patterns. The suitable method for scenario analysis and decomposition are described. A validation of scenarios based on Petri nets is also presented.

8

Czasowy model bloku przetwarzania danych w systemie pomiarowym

Bilski P., Łukaszewski Ł.

Pomiary Automatyka Kontrola

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2007

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R. 53, nr 9 bis

253--256

PL

Artykuł dotyczy modelowania komputerowych systemów pomiarowo-sterujących (KSPS) uwzględniającej czasowe aspekty przepływu informacji w KSPS. W artykule zamieszczono opis części większych prac dotyczących nowej metody opisu modelu KSPS z wykorzystaniem sieci Petri`ego i narzędzia CPN Tools. Szczegółowo przedstawiono model bloku przetwarzania KSPS. Opisano dokładnie funkcje opóźnień zaimplementowane w modelu oraz metodą ich wyznaczania. Dodatkowo zamieszczono badania opóźnień bloku przetwarzania rzeczywistego KSPS oraz symulacje weryfikujące zaprojektowany model.

EN

The paper presents the method of the distributed measuring and control systems modelling, regarding the time aspects of the information flow inside the system. Results of the work including a new method of the measuring system model description using the Petri nets and CPN Tools are included. The data processing model inside the measuring system was presented in detail with delay functions implemented in the model. The paper is concluded with experimental results, comparing simulations with real measuring system behavior.