Showing papers on "Context-free grammar published in 1988"

Graph Grammars and Their Application to Computer Science: 3rd International Workshop Warrenton, Virginia, Usa, December 2-6, 1986

Abstract: Tutorial introduction to the algebraic approach of graph grammars- May we introduce to you: Hyperedge replacement- An introduction to parallel map generating systems- Set theoretic approaches to graph grammars- An introduction to the NLC way of rewriting graphs- Array grammars- Graph grammar based specification of interconnection structures for massively parallel computation- Towards distributed graph grammars- On partially ordered graph grammars- A representation of graphs by algebraic expressions and its use for graph rewriting systems- On context-free sets of graphs and their monadic second-order theory- Restricting the complexity of regular DNLC languages- Apex graph grammars- Graph grammar engineering: A software specification method- A linguistic formalism for engineering solid modeling- Graph grammars and diagram editing- Graphics and their grammars- On network algebras and recursive equations- Ada-concurrency specified by graph grammars- Basic notions of actor grammars- Embedding rule independent theory of graph grammars- Supporting the software development process with attributed NLC graph grammars- Practical applications of precedence graph grammars- Is parallelism already concurrency? Part 1: Derivations in graph grammars- Is parallelism already concurrency? Part 2: Non-sequential processes in graph grammars- Map OL-systems with edge label control: Comparison of marker and cyclic systems- From 0L and 1L map systems to indeterminate and determinate growth in plant morphogenesis- Fundamentals of edge-label controlled graph grammars- Parallelism analysis in rule-based systems using graph grammars- An efficient algorithm for the solution of hierarchical networks of constraints- A software development environment based on graph technology- Map 0L systems with markers- Graph rewriting with unification and composition- Complexity of pattern generation via planar parallel binary fission/fusion grammars- Applications of L-systems to computer imagery- Advances in array languages- Rosenfeld's cycle grammars and kolam- Application of graph grammars in music composing systems- Boundary NLC and partition controlled graph grammars

Applicability of Indexed Grammars to Natural Languages

Abstract: If we take the class of context-free phrase structure grammars (CFPSGs) and modify it so that (i) grammars are allowed to make use of finite feature systems and (ii) rules are permitted to manipulate the features in arbitrary ways, then what we end up with is equivalent to what we started out with Suppose, however, that we take the class of contextfree phrase structure grammars and modify it so that (i) grammars are allowed to employ a single designated feature that takes stacks of items drawn from some finite set as its values, and (ii) rules are permitted to push items onto, pop items from, and copy the stack What we end up with now is no longer equivalent to the CF-PSGs but is significantly more powerful, namely the indexed grammars (Aho, 1968) This class of grammars has been alluded to a number of times in the recent linguistic literature: by Klein (1981) in connection with nested comparative constructions, by Dahl (1982) in connection with topicalised pronouns, by Engdahl (1982) and Gazdar (1982) in connection with Scandinavian unbounded dependencies, by Huybregts (1984) and Pulman and Ritchie (1984) in connection with Dutch, by Marsh and Partee (1984) in connection with variable binding, and doubtless elsewhere as well

Attribute Grammars: Definitions, Systems and Bibliography

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An augmented context free grammar for discourse

Abstract: This paper presents an augmented context free grammar which describes important features of the surface structure and the semantics of discourse in a formal way, integrating new as well as previously existing insights into a unified framework. The structures covered include lists, narratives, subordinating and coordinating rhetorical relations, topic chains and interruptions. The paper discusses the problem of parsing discourse, and compares different grammatical formalisms which could be used for describing discourse structure.

Source encoding using syntactic information source models

Abstract: The use of syntactic information source models for the source encoding (data compression) of messages is described. Syntactic models formulated using context-free grammars augmented with derivation step probabilities are considered. Using an arithmetic coder as the low-level encoding unit, it is shown how practical encoding systems can be constructed from such models. Application of the techniques to the encoding of syntactically correct Pascal computer programs is described, and additional techniques including the use of symbol tables are introduced. The resultant syntactic encoders achieve compression of Pascal programs approaching 90%. >

Combinatory categorial grammars: generative power and relationship to linear context-free rewriting systems

Abstract: Recent results have established that there is a family of languages that is exactly the class of languages generated by three independently developed grammar formalisms: Tree Adjoining Grammars, Head Grammars, and Linear Indexed Grammars. In this paper we show that Combinatory Categorial Grammars also generates the same class of languages. We discuss the structural descriptions produced by Combinatory Categorial Grammars and compare them to those of grammar formalisms in the class of Linear Context-Free Rewriting Systems. We also discuss certain extensions of Combinatory Categorial Grammars and their effect on the weak generative capacity.

Context-Free-Like Forms for the Phrase-Structure Grammars

Abstract: Some new normal forms for the phrase-structure grammars are presented. Each phrase-structure grammar can be replaced by an equivalent grammar with all of the rules context-free, of the form S→v, where S is the initial symbol, and either two extra rules AB→ ɛ, CD→ ɛ, or two extra rules AB→ ɛ, CC→ ɛ, or two extra rules AA→ ɛ, BBB→ ɛ, or even a single extra rule ABBBA→ ɛ, or a single extra rule ABC→ ɛ.

An experimental parser for systemic grammars

Abstract: We describe a general parsing method for systemic grammars. Systemic grammars contain a paradigmatic analysis of language in addition to structural information, so a parser must assign a set of grammatical features and functions to each constituent in addition to producing a constituent structure. Our method constructs a parser by compiling systemic grammars into the notation of Functional Unification Grammar. The existing methods for parsing with unification grammars have been extended to handle a fuller range of paradigmatic descriptions. In particular, the PATR-II system has been extended by using disjunctive and conditional information in functional descriptions that are attached to phrase structure rules. The method has been tested with a large grammar of English which was originally developed for text generation. This testing is the basis for some observations about the bidirectional use of a grammar.

Object-oriented parallel parsing for context-free grammars

Abstract: This paper describes a new parallel parsing scheme for context-free grammars and our experience of implementing this scheme, and it also reports the result of our simulation for running the parsing program on a massive parallel processor.In our basic parsing scheme, a set of context free grammar rules is represented by a network of processor-like computing agents each having its local memory. Each computing agent in the network corresponds to an occurrence of a non-terminal or terminal symbol appearing in the grammar rules. Computing agents in the network work concurrently and communicate with one another by passing messages which are partial parse trees.This scheme is shown to be fast (0(n*h) time for the first complete parse tree, where n is the length of an input sentence and h is the height of the parse tree) and useful in various modes of parsing such as on-line parsing, overlap parsing, on-line unparsing, pipe-lining to semantics processing, etc. Performance evaluation for implementing this scheme on a massive parallel machine is conducted by distributed event simulation using the Time Warp mechanism/Jefferson85/.Our parsing scheme is implemented in a programming language called ABCL/1 which is designed for object-oriented concurrent programming and used for various concurrent programming /Yonezawa86/. The program is currently runing on standard single-cpu machines such as SUN3s and Symbolics Lisp machines (by simulated parallelism).In our experiment and simulation, a set of about 250 context-free grammar rules specifying a subset of English is represented by the corresponding network of objects (i.e., computing agents) and about 1100 concurrently executable objects are involved.

Learning context-free grammars from structural data in polynomial time

Abstract: We consider the problem of learning a context-free grammar from its structural descriptions. Structural descriptions of a context-free grammar are unlabelled derivation trees of the grammar. We present an efficient algorithm for learning context-free grammars using two types of queries: structural equivalence queries and structural membership queries. The learning protocol is based on what is called “minimally adequate teacher”, and it is shown that a grammar learned by the algorithm is not only a correct grammar, i.e. equivalent to the unknown grammar but also structurally equivalent to it. Furthermore, the algorithm runs in time polynomial in the number of states of the minimum frontier-to-root tree automaton for the set of structural descriptions of the unknown grammar and the maximum size of any counter-example returned by a structural equivalence query.

An object-oriented metaprogramming system

Abstract: The Mjolner programming environment is discussed. A number of tools in this environment are metaprograms, i.e., programs that manipulate other programs. The metaprogramming system is grammar-based in the sense that a metaprogramming tool may be generated from the grammar of any language. For each syntactic category of the language, a corresponding class is generated. The syntactic hierarchy of the grammar is mapped into a corresponding class hierarchy. This object-oriented representation of programs is further exploited by including a set of more general classes that view a program as an abstract syntax tree and by allowing the user to add semantic attributes in subclasses. >

Formal manipulation of Forrester diagrams by graph grammars

Abstract: A grammar that formally constructs the types of diagrams used in system dynamics is fully described. It belongs to the special kinds of grammars (attributed programmed graph grammars) that are applied to the construction of graphs and geometric figures. The flow diagrams used in system dynamics have been defined by 'attributed graphs' so that the approach could be applied. The grammar manipulates the graphs according to the requirements of the methodology. Basically, a method to achieve a formal program for interactive modeling upon any diagram, starting from the formal specification of the diagram, is presented. >

Syntactic analysis for large vocabulary speech recognition using a context-free covering grammar

Abstract: The authors describe a syntactive component for large vocabulary speech recognition that incorporates a context-free covering grammar as the language model. The component comprises two modules: a preprocessing module and a syntactic analysis module. The preprocessing module consists of a lexical and a grammar preprocessor. The preprocessors facilitate grammar development. The syntactic analysis module consists of an error correcting maximum likelihood Cocke-Younger-Kasami parser and a context-free covering grammar. The parsar determines the sentence of maximum likelihood accepted by the grammar with respect to a word log likelihood matrix supplied b the acoustic/phonetic component of the speech recognition system. The effectiveness of this type of syntactic analysis was tested in a simulation using a 1040 word vocabulary. Results and error correcting examples are given. >

The OI-hierarchy is closed under control

Abstract: Controlling the derivations of high level grammars by high level languages does not influence their generating power.

Gaifman's theorem on categorial grammars revisited

Abstract: The equivalence of (classical) categorial grammars and context-free grammars, proved by Gaifman [4], is a very basic result of the theory of formal grammars (an essentially equivalent result is known as the Greibach normal form theorem [1], [14]). We analyse the contents of Gaifman's theorem within the framework of structure and type transformations. We give a new proof of this theorem which relies on the algebra of phrase structures and exhibit a possibility to justify the key construction used in Gaifman's proof by means of the Lambek calculus of syntactic types [15].

Attribute grammar based theorem prover

Abstract: In this paper a software tool called attribute grammar based theorem prover (AGBTP) is proposed, which can be used both as a processor of attribute grammars and as a theorem prover. Hence, attribute grammars' applications from the area of software engineering as well as theorem proving applications from the area of knowledge engineering can be faced using the same tool. The main advantages of the proposed tool are that it can combine procedural and declarative characteristics using a very high level language i.e. the attribute grammars' language and user defined semantic functions in the host language. Second, full theorem proving capabilities are obtained through an extended parser, which implements the model elimination procedure.

Language specification by multi-axiom grammars

Abstract: Multiaxiom grammars and language, presented as generalizations of context-free grammars and languages, are defined and used as a mechanism for programming language specification and implementation It is shown how to divide such a grammar into a sequence of subgrammars that generate inductively the language specified by the original grammar Furthermore, it is shown how to use this sequence of subgrammars for inductive language recognition by a process of tokenizing Two classes of algorithms for languages parsing based on multi-axiom grammars are developed: an algorithm obtained by generalizing context-free LR-parsers to multi-axiom grammars, and a pattern-matching algorithm that results from the ability to layer a multi-axiom language into levels such that each sublanguage is independent of the language that contains it The implications of multi-axiom grammars for compiler code generation are briefly discussed >

Speech recognition in VODIS II

Abstract: VODIS is a UK Alvey sponsored project to develop Voice Operated Database Inquiry Systems. A key goal of the project is to investigate ways in which higher level knowledge such as syntax and dialog context can be used to improve the performance of existing speech recognition devices. This paper describes VODIS II, a research system in which recognition is based on the conventional one-pass connected word algorithm but extended in two ways. Firstly, syntactic constraints can be applied directly via context free grammar rules. Secondly, the algorithm generates a lattice of candidate word matches rather than a single globally optimal sequence. This lattice is then processed by a chart parser and an intelligent dialogue controller to obtain the most plausible interpretations of the input. >

Attribute grammars and dataflow computing

Abstract: The use of attribute grammars as a tool for extracting the inherent parallelism of computational algorithms is described. The computational algorithms are expressed as attribute grammars and they are translated into a new form that specifies the dependencies among the various required operations. This form is suitable for parallel execution by dataflow computers.

Controlled Rewriting Using Productions and Reductions.

Abstract: We investigate context-free grammars the rules of which can be used in a productive and in a reductive fashion, while the application of these rules is controlled by a regular language. We distinguish several modes of derivation for this kind of grammar. The resulting language families (properly) extend the family of context-free languages. We establish some closure properties of these language families and some grammatical transformations which yield a few normal forms for this type of grammar. Finally, we consider some special cases (viz. the context-free grammar is linear or left-linear), and generalizations, in particular, the use of arbitrary rather than regular control languages.

A convenient way to incorporate semantic actions in two-pass compiling schemes

Abstract: We present a simple method for connecting semantic actions to parsers. Although applicable to any kind of parser it is especially suited for LR parsers. The method is based on the idea of separating syntax analysis and semantic processing and executing semantic actions by procedures, similar to those of a recursive descent compiler. The procedures are driven by structural information about the source program, which is collected during parsing. The method is applicable to L-attributed grammars. It can be incorporated easily into any existing parser.

A process-activation based parsing algorithm for the development of Natural Language Grammars

Abstract: A running system, named SAIL, for the development of Natural Language Grammars is described. Stress is put on the particular grammar rule model adopted, named Complex Grammar Units, and on the parsing algorithm that runs rules written in according to this model. Moreover, the parser is like a processor and sees grammar rules as processes which can be activated or inactivated, and can handle exchange of information, structured as messages, among rules for long distance analysis. A brief description of the framework of SAIL a user can interact with, named SIS, is also given. Finally, an example shows that different grammar formalisms can be implemented into the frame of SAIL.

Controlled Bidirectional Grammars

Abstract: We investigate context-free grammars the rules of which can be used in a productive and in a reductive fashion, while the application of these rules is controlled by a regular language. We distinguish several modes of derivation for this kind of grammar. The resulting language families (properly) extend the family of context-free languages. We establish some closure properties of these language families and some grammatical transformations which yield a few normal forms for this type of grammar. Finally, we consider some special cases (viz. the context-free grammar is linear or left-linear), and generalizations, in particular, the use of arbitrary rather than regular control languages.