Showing papers on "Tree-adjoining grammar published in 1989"

Regulated rewriting in formal language theory

Abstract: It is well-known that context-free grammars cannot cover all aspects of natural languages, progamming languages and other related fields. Therefore a lot of mechanisms have been introduced which control the application of context-free rules. This book presents 25 different regulating mechanisms by definitions, examples and basic facts, especially concerning hierarchies. Matrix, programmed, and random context grammars as typical representants are studied in more detail. Besides their algebraic and decidability properties a comparison is made with respect to syntactic complexity measures and pure versions. Further topics are combinations of some control mechanisms, regulated L systems, automata characterizations, Szilard languages, and grammar forms of regulated grammars as well as selective substitution grammars as one common generalization.

Slot Grammar: A System for Simpler Construction of Practical Natural Language Grammars

Abstract: Slot Grammar makes it easier to write practical, broad-coverage natural language grammars, for the following reasons. (a) The system has a lexicalist character; although there are grammar rules, they are fewer in number and simpler because analysis is largely data-driven through use of slots taken from lexical entries. (b) There is a modular treatment of different grammatical phenomena through different rule types, for instance rule types for expressing linear ordering constraints. This modularity also reduces the differences between the Slot Grammars of different languages. (c) Several grammatical phenomena, such as coordination and extraposition, are treated mainly in a language-independent shell provided with the system.

Categorial grammars determined from linguistic data by unification

Abstract: We provide an algorithm for determining a categorial grammar from linguistic data that essentially uses unification of type-schemes assigned to atoms. The algorithm presented here extends an earlier one restricted to rigid categorial grammars, introduced in [4] and [5], by admitting non-rigid outputs. The key innovation is the notion of an optimal unifier, a natural generalization of that of a most general unifier.

Scannerless NSLR(1) parsing of programming languages

Abstract: The disadvantages of traditional two-phase parsing (a scanner phase preprocessing input for a parser phase) are discussed. We present metalanguage enhancements for context-free grammars that allow the syntax of programming languages to be completely described in a single grammar. The enhancements consist of two new grammar rules, the exclusion rule, and the adjacency-restriction rule. We also present parser construction techniques for building parsers from these enhanced grammars, that eliminate the need for a scanner phase.

Data processing system implemented process and compiling technique for performing context-free parsing algorithm based on register vector grammar

Abstract: A context-free parsing algorithm employing register vector grammars provides fast parsing of natural languages A compiler for register vector grammars accepts input grammars as standard phase structure rules and generates strongly equivalent grammars in register vector grammar form By applying the context-free register vector grammar parsing algorithm to the resulting grammars, strings may be parsed and trees may be constructed in the same manner performed with phase structure grammar

A grammar-based approach towards unifying hierarchical data models

Abstract: A simple model for representing the hierarchical structure of information is proposed. This model, called the grammatical model, is based on trees that are generated by grammars; the grammars describe the hierarchy of the information represented by the trees. Two transformation languages, an algebra and a calculus, are presented and shown to be equally expressive.

Context-Free NCE Graph Grammars

Abstract: The aim of this paper is to show some close relationships between context-free graph grammars and concepts from string language theory and tree language theory. There are many kinds of context-free graph grammars (see, e.g., [EhrNagRozRos]). Some are node rewriting and others are edge rewriting. In both cases a production of the grammar is of the form X ~ (D,B). Application of such a production to a labeled graph H consists of removing a node (or edge) labeled X from H, replacing it by the graph D, and connecting D to the remainder of H according to the embedding procedure B. Since these grammars are context-free in the sense that one node (or edge) is replaced, their derivations can be modeled by derivation trees, as in the case of strings. However, the grammar may still be context-sensitive in the sense that the (edges of the) graph generated according to the derivation tree may depend on the order in which the productions are applied. A graph grammar that does not suffer from this context-sensitivity is said to be confluent (or to have the finite Church-Rosser property), see [Cou] for a uniform treatment. Thus, for a confluent graph grammar G, each derivation tree of G yields a unique graph in the graph language generated by G. Due to this close relationship to (derivation) trees, the generated graph languages can be described in terms of regular tree languages and regular string languages. We will show this for the particular case of the (node rewriting) edNCE graph grammars, studied in [Kau, Bral/2, EngLeiRozl/2, Sch, EngLeiWel, EngLeil/2, EngRoz] (and called DNELC grammars in [Bra2]).

How to cover a grammar

Abstract: A novel formalism is presented for Earley-like parsers. It accommodates the simulation of non-deterministic pushdown automata. In particular, the theory is applied to non-deterministic LR-parsers for RTN grammars.

Context-sensitivity of two-dimensional regular array grammars

Abstract: Regular array grammars (RAGs) are the lowest subclass in the Chomsky-like hierarchy of isometric array grammars. The left-hand side of each rewriting rule of RAGs has one nonterminal symbol and at most one "#" (a blank symbol). Therefore, the rewriting rules cannot sense contexts of non-# symbols. However, they can sense # as a kind of context. In this paper, we investigate this #-sensing ability. and study the language generating power of RAGs. Making good use of this ability, We show a method for RAGs to sense the contexts of local shapes of a host array in a derivation. Using this method, we give RAGs which generate the sets of all solid upright rectangles and all solid squares. On the other hand. it is proved that there is no context-free array grammar (and thus no RAG) which generates the set of all hollow upright rectangles.

Graph grammars, a new paradigm for implementing visual languages

Abstract: This paper is a report on an ongoing work which started in 1981 and is aiming at a general method which would help to considerably reduce the time necessary to develop a syntax-directed editor for any given diagram technique. The main idea behind the approach is to represent diagrams by (formal) graphs whose nodes are enriched with attributes. Then, any manipulation of a diagram (typically the insertion of an arrow, a box, text, coloring, etc.) can be expressed in terms of the manipulation of its underlying attributed representation graph. The formal description of the manipulation is done by programmed attributed graph grammars.

The modular grammars

Abstract: In this article a new class of grammars with derivation restrictions (similar to the matrix, conditional ones, etc.) is presented. In this situation, if a rule of a subset peculiar to P is used in a derivation then it is compulsory to use only productions of that particular subset as long as it is possible. According to the Chomsky hierarchy, naturally attributed to the grammars the generative power of the modular grammars is studied (Section 2), a series of results being obtained as well as a normal form similar to Chomsky's normal one. The following two paragraphs deal with the closure properties—only for ℳ 2 and (proving that ℳ 2 is AFL) and also with decision problems connected with the modular grammars, using algorithmical proofs in general.

On hyperedge replacement and BNCL graph grammars

Abstract: It is shown that up to vertex labelling BNLC grammars of bounded nonterminal degree generate the same languages of simple graphs as hyperedge replacement grammars. This does not hold if the vertex labelling is taken into account. Vice versa hyperedge replacement grammars generate the same languages of simple graphs as BNLC grammars of bounded nonterminal degree. Furthermore the generation of loops and multiple edges by hyperedege replacement grammars is discussed.

Describing distributed systems by categorical graph grammars

Abstract: The structure of an asynchronous system of processes is described by a labeled hypergraph. It represents both the past and the present of the system. The set of all possible traces is defined by a hypergraph grammar. In the graph, actions and process states are represented by hyperedges. Each hyperedge is connected to some event nodes, some of which are considered to be predecessors of the edge, whereas others are successor nodes. This induces a partial ordering of the hyperedges. Some aspects of the Ada rendezvous are used as an example and translated into hypergraph productions.

Parallel Evaluation of Attribute Grammars.

Abstract: Examines the generation of parallel evaluators for attribute grammars, targeted to shared-memory MIMD computers. Evaluation-time overhead due to process scheduling and synchronization is reduced by detecting coarse-grain parallelism (as opposed to the naive one-process-per-node approach). As a means to more clearly expose inherent parallelism, it is shown how to automatically transform productions of the form X to Y X into list-productions of the form X to Y/sup +/. This transformation allows for many simplifications to be applied to the semantic rules, which can expose a significant degree of inherent parallelism, and thus further increase the evaluator's performance. Effectively, this constitutes an extension of the concept of attribute grammars to the level of abstract syntax. >

A generalizationnof the offline parsable grammars

Abstract: The offline parsable grammars apparently have enough formal power to describe human language, yet the parsing problem for these grammars is solvable. Unfortunately they exclude grammars that use x-bar theory - and these grammars have strong linguistic justification. We define a more general class of unification grammars, which admits x-bar grammars while preserving the desirable properties of offline parsable grammars.

Resolving circularity in attribute grammars with applications to data flow analysis (preliminary version)

Abstract: Circular attribute grammars appear in many data flow analysis problems. As one way of making the notion useful, an automatic translation of circular attribute grammars to equivalent non-circular attribute grammars is presented. It is shown that for circular attribute grammars that arise in many data flow analysis problems, the translation does not increase the asymptotic complexity of the semantic equations. Therefore, the translation may be used in conjunction with any evaluator generator to automate the development of efficient data flow analysis algorithms. As a result, the integration of such algorithms with other parts of a compiler becomes easier.

Generating rectangles using two-dimensional grammars with time and space complexity analyses

Abstract: A two-dimensional grammar for generating all possible rectangles is presented and illustrated by examples. The time and space complexity analyses of this grammar together with a parallel context-free array grammar and a free grammar are also presented. Generating pictures using two-dimensional grammars appear to be a fertile field for further study. The study of two-dimensional grammars has useful applications in region filling. pattern recognition. robotics, pictorial information system design and related areas.

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.

Extending attribute grammar and type inference algorithms

Abstract: Gated attribute grammars and error-tolerant unification expand upon the usual views of attribute grammars and unification. Normally, attribute grammars are constrained to be noncircular; gated attribute grammars allow fairly general circularities. Most unification algorithms do not behave well when given inconsistent input; the new unification paradigm proposed here not only tolerates inconsistencies but extracts information from them. The expanded views prove to be useful in interactive language-based programming environments. Generalized unification allows the environment to help the user find the sources of type errors in a program, while gated attribute grammars allow the environment to provide an interpreter for incremental reevaluation of programs after small changes to the code. The defining feature of gated attribute grammars is the appearance of a gate attribute (indicating where cycle evaluation should begin and end) within every cycle. Attributes are ordered by collapsing strongly connected components in the dependency graph and topologically sorting the result. The smaller dependency graph for each component (ignoring edges leading to the gate) can be recursively collapsed to provide further ordering. Use of the evaluation order defined in this manner allows gated attribute grammars to do without the restrictions on functions within a component needed by the other varieties of circular attribute grammars. Initial and incremental evaluation algorithms are given, as well as a sample grammar allowing an editor for a small language to become an incremental interpreter. Counting unification defines unique solutions to sets of input equations that contain conflicting type information. These solutions are derived from the potential variable constraints implied by the input equations. For each type variable, each branch (a portion of a constraint) is assigned a weight indicating the number of times the input set implied such a constraint. When the input equations are derived from the static analysis of a program, the relative branch weights for a conflicting variable give the overall pattern of uses of that variable and can direct attention to parts of the program that disagree with the majority of uses. A number of error-tolerant unification algorithms are presented.

Compiling phrase structure grammar rules into register vector grammar

Abstract: A procedure is described for compiling context-free phrase structure grammar (PSG) rules into equivalent context-free register vector grammars (RVG). The procedure makes use of finite-state automata (FSA) as an intermediate form, as well as standard FSA transformation and reduction algorithms to minimize the size of the resulting register vector grammars. An example using the syntax of English auxiliary verbs demonstrated the use of FSA in the translation process, and it was shown that such automata must be reduced to yield fewer RVG productions. It was also shown that an additional optimization phase is needed to further reduce the size and increase the efficiency of register vector grammars. The PSG-to-RVG compiler enables natural-language interface developers to design grammars at the phrase structure rule level, but execute them at the register vector grammar level. This approach maximizes both the understandability and efficiency of syntactic analysis. >

Learning regular grammars on connection architectures

Abstract: The authors present results on learning regular grammars as well as developing extensions to learning multidimensional random fields. In learning a regular grammar, they use recent results on the stochastic representation of strongly connected regular grammars in order to derive an algorithm based on mutual information for learning the minimal state set as well as the production rules of the grammar. These learning results are then extended to multiple dimensions by extending the state structure of the regular grammar to the neighborhood structure of multidimensional random fields. This allows the authors to learn textures for image segmentation and reconstruction. The implementation of the learning algorithms on connection architectures is described. >

Coordinate grammars revisited: generalized isometric grammars

Abstract: In a "coordinate grammar", the rewriting rules replace sets of symbols having been given coordinates by sets of symbols whose coordinates are given functions of the coordinates of the original symbols. It was shown in 1972 that coordinate grammars are "too powerful"; even if the rules are all of finite-state types and the functions are all computable by finite transducers, the grammar has the power of a Turing machine. This paper shows that if we require the functions to be shift-invariant and the rules to be of bounded diameter, then such grammars do have a useful hierarchy of types; in fact, when we require that their sentential forms always remain connected, they turn out to be equivalent to "isometric grammars".

Regular attribute grammars and finite state machines

Abstract: A regular attribute grammar is an attribute grammar with an underlying context-free grammar which is right or left linear. The restriction to regular underlying grammars restricts the possible dependencies between attributes; this in turn permits efficient algorithms for attribute evaluation. An algorithm for performing attribute evaluation in parallel with a single scan of the input by a deterministic finite state machine is developed. Special cases of regular attribute grammars for which the algorithm uses very little space are identified. Several examples are included.

Analysis and generation grammars

Abstract: This paper describes the analysis and generation grammars for English and Japanese as they were employed in the KBMT-89 program. We discuss word order, coordination, subcategorization, morphological rules, rule ordering and bi-directional grammars.

An evaluation of lexicalization in parsing

Abstract: In this paper, we evaluate a two-pass parsing strategy proposed for the so-called 'lexicalized' grammar. In 'lexicalized' grammars (Schabes, Abeille and Joshi, 1988), each elementary structure is systematically associated with a lexical item called anchor. These structures specify extended domains of locality (as compared to CFGs) over which constraints can be stated. The 'grammar' consists of a lexicon where each lexical item is associated with a finite number of structures for which that item is the anchor. There are no separate grammar rules. There are, of course, 'rules' which tell us how these structures are combined.A general two-pass parsing strategy for 'lexicalized' grammars follows naturally. In the first stage, the parser selects a set of elementary structures associated with the lexical items in the input sentence, and in the second stage the sentence is parsed with respect to this set. We evaluate this strategy with respect to two characteristics. First, the amount of filtering on the entire grammar is evaluated: once the first pass is performed, the parser uses only a subset of the grammar. Second, we evaluate the use of non-local information: the structures selected during the first pass encode the morphological value (and therefore the position in the string) of their anchor; this enables the parser to use non-local information to guide its search.We take Lexicalized Tree Adjoining Grammars as an instance of lexicalized grammar. We illustrate the organization of the grammar. Then we show how a general Earley-type TAG parser (Schabes and Joshi, 1988) can take advantage of lexicalization. Empirical data show that the filtering of the grammar and the non-local information provided by the two-pass strategy improve the performance of the parser.