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A Notion of Non-Interference for Timed Automata (Extended Abstract)
No full textRoberto Barbuti , Nicoletta De Francesco , Antonella Santone , Luca Tesei Dipartimento di Informatica, Universita di Pisa Corso Italia, 40, 56125 Pisa - Italy e-mail: fbarbuti, [email protected] Dipartimento di Ingegneria dell'Informazione, Universita di Pisa Via Diotisalvi, 2, 56126 Pisa - Italy e-mail: fnicoletta.defrancesco, [email protected] Abstract The non-interference property of concurrent systems is a security property concerning the ow of information among dierent levels of security of the system. If we suppose that the behavior of the system is divided into a high security behavior and low security behavior, we say that the system respects the non-interference property if the low-level behavior is not aected by the high-level one. In this paper we discuss a notion of non-interference for real-time systems, where the time is a crucial parameter
Timed Automata with Urgent Transitions
No full textIn this paper we propose an extension to the formalism of timed automata by allowing urgent transitions. A urgent transition is a transition which must be taken within a fixed time interval from its enabling time. We give a set of rules formally describing the behaviour of urgent transitions and we show that, from a language theoretic point of view, the addition of urgency does not improve the expressive power of timed automata. However, from a specification point of view, the use of urgent transitions is crucial, especially in modular specification of systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
A Notion of Non-Interference for Timed Automata
No full textThe non-interference property of concurrent systems is a security property concerning the flow of information among different levels of security of the system. In this paper we introduce a notion of timed non-interference for real-time systems specified by timed automata.The notion is presented using an automata based approach and then it is characterized also by operations and equivalence between timed languages. The definition is applied to an example of a time-critical system modeling a simplified control of an airplane
Abstract Interpretation and Model Checking for Checking Secure Information Flow in Concurrent Systems
No full textWe propose a method to check secure information flow in concurrent programs with synchronization. The method is based on the combination of abstract interpretation and model checking: by abstract interpretation we build a finite representation (transition system)
of the behavior of the program. Then we model check the abstract transition system with respect to the security properties, expressed by a set of temporal logic formulae. The approach allows certifying more programs than previous methods do. The main point is that we are able to check more carefully the scope of indirect information flows
Variations on the Author
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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