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1.
Discrete time model for process meta language with fictitious-clock
Boštjan Vlaovič, Aleksander Vreže, 2022, original scientific article

Abstract: Industries like telecommunications, medical, automotive, military, avionics, and aerospace use complex real-time systems. Specification and Description Language (SDL) is one of the leading domain specific languages that is formally defined by international standards and well established in describing such systems. To check system properties abstracted model of the system is prepared in selected modeling language. We use Spin (Simple Promela Interpreter) model checker that is one of the leading tools for verification of complex concurrent and reactive systems. This paper focuses on modeling the SDL timer construct. It is one of the SDL constructs that is not easily modeled with Promela, but is present in many SDL systems. After an overview of the related work we propose a new Discrete Time Model for Promela (DTMP) that is seamlessly integrated in our framework for modeling SDL systems and can be used with the mainstream version of the Spin tool. To the best of our knowledge, this is not possible with the existing solutions. We describe how DTMP can be used to model SDL systems that use timers. Experimental results demonstrate its applicability to non-SDL systems with Fischer’s mutual exclusion protocol and the Parallel Acknowledgment with Retransmission that were used in prior studies. We compare state-space requirements with one of the existing solutions DT Promela and DT Spin. With that, virtues and shortcomings of this high-level solution are exposed. We have shown that DTMP is effective when an extensive range of timer expiration values are used, which is usually the case in real-life SDL systems.
Keywords: formal specifications, formal languages, discrete time, model checking, automated extraction, SDL, Promela, SpinRCP, Sdl2pml
Published in DKUM: 27.03.2025; Views: 0; Downloads: 6
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2.
Mixed-integer nonlinear programming based optimal time scheduling of construction projects under nonconvex costs
Rok Cajzek, Uroš Klanšek, 2016, original scientific article

Abstract: Optimal project scheduling under nonconvex time-cost relations represents a challenging problem in construction management. The nonconvex time-cost relations may appear in a construction project when several different duration options are available for its activities due to alternative technological processes enabled for their realization or wide accessibility of production resources. The source of nonconvexity of the project scheduling optimization problem can also be the project penalty- or bonus-duration relations arranged within the construction contract. The aim of this paper is to present the mixed-integer nonlinear programming (MINLP) based optimal time scheduling of construction projects under nonconvex costs. For this purpose, the MINLP model was developed and applied. A numerical example from literature and an example of construction project time-cost trade-off analysis under practical nonconvex penalty function are given in the paper to demonstrate advantages of MINLP optimization. The example from literature first presented the capability of the MINLP approach to obtain the optimal solution for difficult, highly combinatorial nonconvex discrete project scheduling problem. Thereupon, the following example revealed that the optimal project time-cost curve may take very nonuniform shape on account of discrete nature of activity direct cost options and nonconvex relation between project duration and total cost. In this way, the presented study intends to provide practitioners with new information from the field of optimization techniques for project scheduling as well as an alternative view on performance of total cost when project duration is changed.
Keywords: extreme environments, construction management, discrete optimization, mixed-integer nonlinear programming, nonconvex costs, time scheduling
Published in DKUM: 12.07.2017; Views: 1577; Downloads: 437
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