1,721,166 research outputs found
Rule-based modeling and static analysis of self-adaptive systems by graph transformation
No full textSoftware systems nowadays require continuous operation despite changes both in user needs and in their operational environments. Self-adaptive systems are typically instrumented with tools to autonomously perform adaptation to these changes while maintaining some desired properties. In this paper we model and analyze self-adaptive systems by means of typed, attributed graph grammars. The interplay of different grammars representing the application and the adaptation logic is realized by an adaption manager. Within this formal framework we define consistency and operational properties that are maintained despite adaptations and we give static conditions for their verification. The overall approach is supported by the AGG tool for modeling, simulating, and analyzing graph transformation systems. A case study modeling a business process that adapts to changing environment conditions is used to demonstrate and validate the formal framework
Open Petri nets: Non-deterministic Processes and Compositionality
No full textWe introduce ranked open nets, a reactive extension of Petri
nets which generalises a basic open net model introduced in a previous
work by allowing for a refined notion of interface. The interface towards
the external environment of a ranked open net is given by a subset
of places designated as open and used for composition. Additionally, a
bound on the number of connections which are allowed on an open place
can be specified. We show that the non-deterministic process semantics
is compositional with respect to the composition operation over ranked
open nets, a result which did not hold for basic open nets
Rule-based modeling and static analysis of self-adaptive systems by graph transformation
No full textSoftware systems nowadays require continuous operation despite changes both in user needs and in their operational environments. Self-adaptive systems are typically instrumented with tools to autonomously perform adaptation to these changes while maintaining some desired properties. In this paper we model and analyze self-adaptive systems by means of typed, attributed graph grammars. The interplay of different grammars representing the application and the adaptation logic is realized by an adaption manager. Within this formal framework we define consistency and operational properties that are maintained despite adaptations and we give static conditions for their verification. The overall approach is supported by the AGG tool for modeling, simulating, and analyzing graph transformation systems. A case study modeling a business process that adapts to changing environment conditions is used to demonstrate and validate the formal framework
Process Bisimulation via a Graphical Encoding
No full textThe paper presents a case study on the synthesis of labelled transition systems (LTSs) for process calculi, choosing as testbed Milner's Calculus of Communicating System (CCS). The proposal is based on a graphical encoding: each CCS process is mapped into a graph equipped with suitable, such that the denotation is fully abstract with respect to the usual structural congruence. Graphs with interfaces are amenable to the synthesis mechanism based on borrowed contexts (BCs), proposed by Ehrig and Koenig (which are an instance of relative pushouts, originally introduced by Milner and Leifer). The BC mechanism allows the effective construction of an LTS that has graphs with interfaces as both states and labels, and such that the associated bisimilarity is automatically a congruence. Our paper focuses on the analysis of the LTS distilled by exploiting the encoding of CCS processes: besides offering some technical contributions towards the simplification of the BC mechanism, the key result of our work is the proof that the bisimilarity on processes obtained via BCs coincides with the standard strong bisimilarity for CCS
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
Constructs for Programming with Graph Rewrites
Full text linkGraph rewriting is becoming increasingly popular as a method for programming with graph based data structures. We present several modifications to a basic serial graph rewriting paradigm and discuss how they improve coding programs in the Grrr graph rewriting programming language. The constructs we present are once only nodes, attractor nodes and single match rewrites. We illustrate the operation of the constructs by example. The advantages of adding these new rewrite modifiers is to reduce the size of programs, improve the efficiency of execution and simplify the host graph undergoing rewriting
Parallel composition and unfolding semantics of graph grammars
Full text linkThe main aims of this thesis are to provide an approach to the parallel composition of graph grammars and a semantics for graph grammars, called the unfolding semantics, in which the aspects of concurrency and compositionality with respect to the parallel composition play a central role. The parallel composition of graph grammar allows the composition of grammars with respect to a shared part (that may be empty), and is based on parallel and amalgamated composition of the rules of the component grammars. Moreover, the result of the composition is suitably syntactically and semantically related to the component grammars. The unfolding semantics of a graph grammar is a true concurrent, branching structure semantics in which states (graphs) as well as changes of states (derivations) are represented. The unfolding can be constructed incrementally, and we show that this yields the same result as a construction based on gluing of the deterministic computations of a grammar. Moreover, the unfolding of a graph grammar is itself a graph grammar that belong to a special class of graph grammars: the occurrence graph grammars. Here this class is defined axiomatically, and the members of this class can be seen as grammars that represent (deterministic and non-deterministic) computations of another grammars. The semantics of a grammar obtained as the parallel composition of other grammars is isomorphic to the composition of the semantics of the component grammars. As the purpose of the parallel composition is to be a composition for concurrent and reactive systems, the fact that this composition is compatible with a true concurrency semantics is an attractive result.Das Hauptziel dieser Arbeit ist es, einen Ansatz fur die parallele Komposition von Graph- Grammatiken und eine Unfolding-Semantik genannte Semantik fiir Graph-Grammatiken bereitzustcllen, in der die Aspekte Nebenlaufigkeit und Kompositionalitat bzgl. der parallelen Komposition eine zentrale Rolle einnehmen. Die parallele Komposition von Graph-Grammatiken erlaubt die Komposition von Grammatiken bzgl. eines gemeinsamen (moglicherweise leeren) Anteils und basiert auf der parallelen und amalgamierten Komposition von Regeln der komponierten Grammtiken. Dariiber hinaus ist das Kompositionsergebnis syntaktisch und semantisch in geeigneter Weise mit den komponierten Grammatiken verkniipft. Die Unfolding-Semantik einer Graph-Grammatik ist eine echt nebenldufige, verzweigende Semantik, in der sowohl Zustande (Graphen) als auch Zustandsanderungen (Ableitungen) reprasentiert sind. Das Unfolding kann inkrementell konstruiert werden und es wird gezeigt, daß dies das gleiche Result liefert wie die Verklebung der deterministischen Berechnungen einer Grammatik Dartiberhinaus ist das Unfolding einer Graph-Grammatik selbst eine Graph- Grammatik, die einer speziellen Klasse von Graph-Grammatiken angehOrt: den Occurrence- Grammatiken. Hier wird diese Klasse axiomatisch definiert und die Elemente dieser Klasse kOnnen als Grammatiken gesehen werden, die (deterministische und nicht-deterministische) Berechnungen einer anderen Grammatik reprdsentieren. Die Semantik einer Grammatik, die aus der parallelen Komposition anderer Grammatiken entstanden ist, ist isomorph zur Komposition der Semantiken der komponierten Grammatiken. Dieses Kompatibilitatsresultat verbindet die parallele Komposition und die Unfolding Semantik in enger Weise. Da der Zweck der parallelen Komposition die Komposition nebenldufiger Systeme ist, stellt die Kompatibiliat von Komposition und Nebenlaufigkeitssemantik ein attraktives Ergebnis dar
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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