1,720,969 research outputs found
Static BiLog: a Unifying Language for Spatial Structures
No full textAiming at a unified view of the logics describing spatial structures, we introduce a general framework, BiLog, whose formulae characterise monoidal categories. As a first instance of the framework we consider bigraphs, which are emerging as a an interesting (meta-)model for spatial structures and distributed calculi. Since bigraphs are built orthogonally on two structures, a hierarchical place graph for locations and a link (hyper-)graph for connections, we obtain a logic that is a natural composition of other two instances of BiLog: a Place Graph Logic and a Link Graph Logic. We prove that these instances generalise the spatial logics for trees, for graphs and for tree contexts. We also explore the concepts of separation and sharing in these logics. We note that both the operator * of Separation Logic and the operator | of spatial logics do not completely separate the underlying structures. These two different forms of separation can be naturally derived as instances of BiLog by using the complete separation induced by the tensor product of monoidal categories along with some form of sharing
BiLog: Spatial Logics for Bigraphs
No full textBigraphs are emerging as a (meta-)model for concurrent calculi, like CCS, ambients, -calculus, and Petri nets. They are built orthogonally on two structures: a hierarchical place graph for locations and a link (hyper-)graph for connections. Aiming at describing bigraphical structures, we introduce a general framework, BiLog, whose formulae describe arrows in monoidal categories. We then instantiate the framework to bigraphical structures and we obtain a logic that is a natural composition of a place graph logic and a link graph logic. We explore the concepts of separation and sharing in these logics and we prove that they generalise well known spatial logics for trees, graphs and tree contexts. As an application, we show how XML data with links and web services can be modelled by bigraphs and described by BiLog. The framework can be extended by introducing dynamics in the model and a standard temporal modality in the logic. However, in some cases, temporal modalities can be already expressed in the static framework. To testify this, we show how to encode a minimal spatial logic for CCS in an instance of BiLog
A Distributed Kripke Semantics
No full textAn intuitionistic, hybrid modal logic suitable for reasoning about distribution of resources was introduced in [10]. We extend the Kripke semantics of intuitionistic logic, enriching each possible Kripke state with a set of places, and show that this semantics is both sound and complete for the logic. In the semantics, resources of a distributed system are interpreted as atoms, and placement of atoms in a possible state corresponds to the distribution of the resources. The modalities of the logic allow us to validate properties in a particular place, in some place and in all places. We extend the logic with disjunctive connectives, and refine our semantics to obtain soundness and completeness for extended logic. The extended logic can be seen as an instance of Hybrid IS5 [2, 18]
Unwinding in Information Flow Security
No full textWe study information flow security properties which are persistent, in the sense that if a system is secure then all of its reachable states are secure too. We present a uniform characterization of these properties in terms of a general unwinding schema. This unwinding characterization allows us to prove several compositionality properties of the considered security classes. Moreover, we exploit the unwinding condition to dictate the form of the rules we can use to incrementally develop secure processes and to rectify insecure processes
Secure Contexts for Confidential Data
No full textInformation flow security in a mutlilevel system aims at guaranteeing that no high level information is revealed to low level users, even in the presence of any possible malicious process. This requirement could be too demanding when some knowledge about the environment (context) in which the process is going to run is available. To deal with these situations we introduce the notion of secure contexts for a class of processes. This notion is parametric with respect to both the observation equivalence and the operation used to characterize the low level behavior of a process. We mainly analyze the cases of bisimulation and trace equivalence. We describe how to build secure contexts in these cases and we show that two well-known security properties, named BNDC and NDC, are just special instances of our general notion
Unwinding in Information Flow Security
No full textWe study information flow security properties which are persistent, in the sense that if a system is
secure then all of its reachable states are secure too. We present a uniform characterization of these
properties in terms of a general unwinding schema. This unwinding characterization allows us to
prove several compositionality properties of the considered security classes. Moreover, we exploit
the unwinding condition to dictate the form of the rules we can use to incrementally develop secure
processes and to rectify insecure processes
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
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