On the membership problem for regular DNLC grammars

AbstractThere are (at least) three motivations to study the class of regular directed node-label controlled graph grammars (regular DNLC grammars for shor): (1) it fits very well into the hierarchy of subclasses of DNLC grammars, (2) it generalizes naturally right-linear string grammars and (3) it provides a useful framework for the theory of concurrent systems based on the theory of traces.The complexity of (the membership problem for) the class of regular DNLC grammars is investigated

Theory of traces

AbstractThe theory of traces, originated by A. Mazurkiewicz in 1977, is an attempt to provide a mathematical description of the behavior of concurrent systems. Its aim is to reconcile the sequential nature of observations of the system behavior on the one hand and the nonsequential nature of causality between the actions of the system on the other hand.One can see the theory of traces to be rooted in formal string language theory with the notion of partial commutativity playing the central role. Alternatively one can see the theory of traces to be rooted in the theory of labeled acyclic directed graphs (or even in the theory of labeled partial orders).This paper attempts to present a major portion of the theory of traces in a unified way. However, it is not a survey in the sense that a number of new notions are introduced and a number of new results are proved. Although traditionally most of the development in the theory of traces follows the string-language-theoretic line, we try to demonstrate to the reader that the graph-theoretic point of view may be more appropriate.The paper essentially consists of two parts. The first one (Sections 1 through 4) is concerned with the basic theory of traces. The second one (Section 5) presents applications of the theory of traces to the theory of the behavior of concurrent systems, where the basic system model we have chosen is the condition/event system introduced by C.A. Petri

Boundary graph grammars with dynamic edge relabeling

AbstractMost NLC-like graph grammars generate node-labeled graphs. As one of the exceptions, eNCE graph grammars generate graphs with edge labels as well. We investigate this type of graph grammar and show that the use of edge labels (together with the NCE feature) is responsible for some new properties. Especially boundary eNCE (B-eNCE) grammars are considered. First, although eNCE grammars have the context-sensitive feature of “blocking edges,” we show that B-eNCE grammars do not. Second, we show the existence of a Chomsky normal form and a Greibach normal form for B-eNCE grammars. Third, the boundary eNCE languages are characterized in terms of regular tree and string languages. Fourth, we prove that the class of (boundary) eNCE languages properly contains the closure of the class of (boundary) NLC languages under node relabelings. Analogous results are shown for linear eNCE grammars

Ordered Tree Decomposition for HRG Rule Extraction

We present algorithms for extracting Hyperedge Replacement Grammar (HRG) rules from a graph along with a vertex order. Our algorithms are based on finding a tree decomposition of smallest width, relative to the vertex order, and then extracting one rule for each node in this structure. The assumption of a fixed order for the vertices of the input graph makes it possible to solve the problem in polynomial time, in contrast to the fact that the problem of finding optimal tree decompositions for a graph is NP-hard. We also present polynomial-time algorithms for parsing based on our HRGs, where the input is a vertex sequence and the output is a graph structure. The intended application of our algorithms is grammar extraction and parsing for semantic representation of natural language. We apply our algorithms to data annotated with Abstract Meaning Representations and report on the characteristics of the resulting grammars

Algoritmo de membresía para gramáticas de reemplazo de hiperaristas

“Este trabajo trata del problema de membresía en gramáticas de reemplazo de hiperaristas (HRG). Dado un hipergrafo H con nodos e hiperaristas etiquetadas, dirigidas y enraizadas, el problema consiste en determinar si H ∈ L (G), donde G ∈ HRG, es decir si H está ́ en el lenguaje generado por G. Se conoce que el problema de membresía para HRG es, en general, intratable. Sin embargo, este problema se ha resuelto en tiempo polinomial pará algún un tipo restringido de HRG. El objetivo principal de esta investigación es desarrollar un algoritmo correcto con complejidad polinomial que resuelva el problema de membresía en HRG. Para lograr el objetivo fue necesario utilizar una definición ́ alternativa de la matriz de adyacencias para hipergrafos, la cual es una generalización de la matriz de adyacencias para grafos. En este trabajo se obtuvo un algoritmo Analizador, cuya complejidad es del orden O (l5 ), donde l es el número de vértices del hipergrafo de entrada. Este algoritmo lleva acabo el análisis directamente en la Matriz de Adyacencias del hipergrafo H. También, para el algoritmo propuesto se presenta la demostración de su corrección”

Weighted DAG Automata for Semantic Graphs

Graphs have a variety of uses in natural language processing, particularly as representations of linguistic meaning. A deficit in this area of research is a formal framework for creating, combining, and using models involving graphs that parallels the frameworks of finite automata for strings and finite tree automata for trees. A possible starting point for such a framework is the formalism of directed acyclic graph (DAG) automata, defined by Kamimura and Slutzki and extended by Quernheim and Knight. In this article, we study the latter in depth, demonstrating several new results, including a practical recognition algorithm that can be used for inference and learning with models defined on DAG automata. We also propose an extension to graphs with unbounded node degree and show that our results carry over to the extended formalism

Study of application of space telescope science operations software for SIRTF use

The design and development of the Space Telescope Science Operations Ground System (ST SOGS) was evaluated to compile a history of lessons learned that would benefit NASA's Space Infrared Telescope Facility (SIRTF). Forty-nine specific recommendations resulted and were categorized as follows: (1) requirements: a discussion of the content, timeliness and proper allocation of the system and segment requirements and the resulting impact on SOGS development; (2) science instruments: a consideration of the impact of the Science Instrument design and data streams on SOGS software; and (3) contract phasing: an analysis of the impact of beginning the various ST program segments at different times. Approximately half of the software design and source code might be useable for SIRTF. Transportability of this software requires, at minimum, a compatible DEC VAX-based architecture and VMS operating system, system support software similar to that developed for SOGS, and continued evolution of the SIRTF operations concept and requirements such that they remain compatible with ST SOGS operation

Culture as Soft Power

Including a thorough literature review and a number of case studies referred to cultural institutions and organisations, this book sheds light on different usages of culture as a source of soft power. Through an innovative and interdisciplinary approach, it addresses issues tackled in international cultural relations, intellectual history, comparative literature, sociology of literature and global literary studies