Parsing of Hyperedge Replacement Grammars with Graph Parser Combinators

Graph parsing is known to be computationally expensive. For this reason the construction of special-purpose parsers may be beneficial for particular graph languages. In the domain of string languages so-called parser combinators are very popular for writing efficient parsers. Inspired by this approach, we have proposed graph parser combinators in a recent paper, a framework for the rapid development of special-purpose graph parsers. Our basic idea has been to define primitive graph parsers for elementary graph components and a set of combinators for the flexible construction of more advanced graph parsers. Following this approach, a declarative, but also more operational description of a graph language can be given that is a parser at the same time. In this paper we address the question how the process of writing correct parsers on top of our framework can be simplified by demonstrating the translation of hyperedge replacement grammars into graph parsers. The result are recursive descent parsers as known from string parsing with some additional nondeterminism

Graph grammars with string-regulated rewriting

Multicellular organisms undergo a complex developmental process, orchestrated by the genetic information in their cells, in order to form a newborn individual from a fertilized egg. This complex process, not completely understood yet, is believed to have a key role in generating the impressive biotic diversity of organisms found on earth. Inspired by mechanisms of Eukaryotic genetic expression, we propose and analyse graph grammars with string-regulated rewriting. In these grammatical systems a genome sequence is represented by a regulatory string, a graph corresponds to an organism, and a set of graph grammar rules represents different forms of implementing cell division. Accordingly, a graph derivation by the graph grammar resembles the developmental process of an organism. We give examples of the concept and compare its generative power to the power of the traditional context-free graph grammars. We demonstrate that the power of expression increases when genetic regulation is included in the model, as compared to non-regulated grammars. Additionally, we propose a hierarchy of string-regulated graph grammars, arranged by expressive power. These results highlight the key role that the transmission of regulatory information during development has in the emergence of biological diversity.D.L. was supported in part by a research stay fellowship at Otto-von-Guericke-Universität Magdeburg from the Spanish Ministerio de Educación

User support for software development technologies

The adoption of software development technologies is very closely related to the topic of user support. This is especially true in early phases, when the users are not familiar with the modification or the build processes of the software that has to be developed nor with the technology used for software development. This work introduces an approach to improve the usability of software development technologies represented by the Combinatory Logic Synthesizer (CL)S Framework. (CL)S is based on a type inhabitation algorithm for the combinatory logic with intersection types and aims to automatically create software components from a domain-specified repository. The framework yields a complete enumeration of all inhabitants. The inhabitation results are computed in the form of tree grammars. Unfortunately, the underlying type system allows limited application of domain-specific knowledge. To compensate for this limit, this work provides a framework for debugging intersection type specifications and filtering inhabitation results using domain-specific constraints as main aspects. The aim of the debugger is to make potentially incomplete or erroneous input specifications and decisions of the inhabitation algorithm understandable for those who are not experts in the field of type theory. The combination of tree grammars and graph theory forms the foundation of a clear representation of the computed results that informs users about the search process of the algorithm. The graphical representations are based on hypergraphs that illustrate the inhabitation in a step-wise fashion. Within the scope of this work, three filtering algorithms were implemented and investigated. The filtering algorithm integrated into the framework for user support and used for the restriction of inhabitation results is practically feasible and represents a clear improvement compared to existing approaches. It is based on modifying the tree grammars resulting from the (CL)S Framework. Additionally, the usability of the (CL)S Framework is supported by eight perspectives included in a web-based integrated development environment (IDE) that provides detailed graphical and textual information about the synthesis

Toward Semantic Machine Translation

This thesis presents a novel approach to interlingual machine translation using λ-calculus expressions as an intermediate representation. It investigates and extends existing algorithms which learn a combinatorial category grammar for semantic parsing, and introduces two new algorithms for generation out of logical forms inspired by that semantic parser. The results of a set of new experiments for generation and parsing are described, as well as an evaluation of the performance of a semantic translation system created by joining the semantic parser and generator together. Experimental results demonstrate that under certain conditions, this semantic model achieves better performance than a standard phrase-based statistical MT system in both an automated evaluation of translation output and a manual evaluation of adequacy and fluency

In Memoriam, Solomon Marcus

This book commemorates Solomon Marcus’s fifth death anniversary with a selection of articles in mathematics, theoretical computer science, and physics written by authors who work in Marcus’s research fields, some of whom have been influenced by his results and/or have collaborated with him

Multiple Context-Free Tree Grammars: Lexicalization and Characterization

Multiple (simple) context-free tree grammars are investigated, where "simple" means "linear and nondeleting". Every multiple context-free tree grammar that is finitely ambiguous can be lexicalized; i.e., it can be transformed into an equivalent one (generating the same tree language) in which each rule of the grammar contains a lexical symbol. Due to this transformation, the rank of the nonterminals increases at most by 1, and the multiplicity (or fan-out) of the grammar increases at most by the maximal rank of the lexical symbols; in particular, the multiplicity does not increase when all lexical symbols have rank 0. Multiple context-free tree grammars have the same tree generating power as multi-component tree adjoining grammars (provided the latter can use a root-marker). Moreover, every multi-component tree adjoining grammar that is finitely ambiguous can be lexicalized. Multiple context-free tree grammars have the same string generating power as multiple context-free (string) grammars and polynomial time parsing algorithms. A tree language can be generated by a multiple context-free tree grammar if and only if it is the image of a regular tree language under a deterministic finite-copying macro tree transducer. Multiple context-free tree grammars can be used as a synchronous translation device.Comment: 78 pages, 13 figure