1,720,960 research outputs found
Practical efficient modular verification and analysis
No full textThis paper shows how the modular structure of composite systems can guide the state-space exploration in explicit-state linear-time model-checking and make it more efficient in practice. Given a composite system where every module has input and output variables — and variables of different modules can be connected — a total ordering according to which variables are generated is determined, through heuristics based on graph-theoretical analysis of the modular structure. The technique is shown to outperform standard exploration techniques (that do not take the modular structure information into account) by several orders of magnitude in experiments with Spin models of MTL formulas
Tomorrow and all our yesterdays: MTL satisfiability over the integers
No full textWe investigate the satisfiability problem for metric temporal logic (MTL) with both past and future operators over linear discrete bi-infinite time models isomorphic to the integer numbers, where time is unbounded both in the future and in the past. We provide a technique to reduce satisfiability over the integers to satisfiability over the well-known mono-infinite time model of natural numbers, and we show how to implement the technique through an automata-theoretic approach. We also prove that MTL satisfiability over the integers is EXPSPACE-complete, hence the given algorithm is optimal in the worst case
Towards the exhaustive verification of real-time aspects in controller implementation
No full textIn industrial applications, the number of final products endowed with real-time automatic control systems that manage safety-critical situations has dramatically increased. Thus, it is of growing importance that the control system design flow encompasses also its translation into software code and its embedding into a hardware and software network. In this paper, a tool-supported approach to the formal analysis of real-time aspects in controller implementation is proposed. The analysis can ensure that some desired properties of the control loop are preserved in its implementation on a distributed architecture. Moreover, the tool provides as output information which can be used to approach straightforwardly some design problems, such as hardware sizing in the final implementation
On Relaxing Metric Information in Linear Temporal Logic
No full textMetric LTL formulas rely on the next operator to encode time distances, whereas qualitative LTL formulas use only the until operator. This paper shows how to transform any metric LTL formula M into a qualitative formula Q, such that Q is satisfiable if and only if M is satisfiable over words with variability bounded with respect to the largest distances used in M (i.e., occurrences of next), but the size of Q is independent of such distances. Besides the theoretical interest, this result can help simplify the verification of systems with time-granularity heterogeneity, where large distances are required to express the coarse-grain dynamics in terms of fine-grain time units
Automata-based Verification of Linear Temporal Logic Models with Bounded Variability
No full textA model has variability bounded by v/k when the state changes at most v times over any linear interval containing k time instants. When interpreted over models with bounded variability, specification formulae that contain redundant metric information---through the usage of next operators---can be simplified without affecting their validity. This paper shows how to harness this simplification in practice: we present a translation of LTL into Büchi automata that removes redundant metric information, hence makes for more efficient verification over models with bounded variability. To show the feasibility of the approach, we also implement a proof-of-concept translation in ProMeLa and verify it using the Spin off-the-shelf model-checker
Bounded variability of metric temporal logic
Get PDFPrevious work has shown that reasoning with real-time temporal logics is often simpler when restricted to models with bounded variability—where no more than v events may occur every V time units, for given v, V. When reasoning about formulas with intrinsic bounded variability, one can em-ploy the simpler techniques that rely on bounded variability, without any loss of generality. What is then the complexity of algorithmically deciding which formulas have intrinsic bounded variability? In this paper, we study the problem with reference to Metric Tem-poral Logic (MTL). We prove that deciding bounded variability of MTL formulas is undecidable over dense-time models, but with a undecidability degree lower than generic dense-time MTL satisfiability. Over discrete-time models, instead, deciding MTL bounded variability has the same exponential-space complexity as satisfiability. To complement these nega-tive results, we also briefly discuss small fragments of MTL that are more amenable to reasoning about bounded variability. 1 The Benefits of Bounding Variability In yet another instance of the principle that “there ain’t no such thing as a free lunch”, expressiveness of formal languages comes with a significant cost to pay in terms of complexity—and possibly undecidability—of algorithmic analysis. The trade-off between expressiveness and complexity is particularly critical for the real-time temporal logics, which dwell on the border of intractability. A chief research challenge is, therefore, identifying expressive temporal logic fragments without letting the “dark side ” of undecidability [6] prevail and abate practical usability
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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