13,937 research outputs found
A Note on the Complexity of Restricted Attribute-Value Grammars
The recognition problem for attribute-value grammars (AVGs) was shown to be
undecidable by Johnson in 1988. Therefore, the general form of AVGs is of no
practical use. In this paper we study a very restricted form of AVG, for which
the recognition problem is decidable (though still NP-complete), the R-AVG. We
show that the R-AVG formalism captures all of the context free languages and
more, and introduce a variation on the so-called `off-line parsability
constraint', the `honest parsability constraint', which lets different types of
R-AVG coincide precisely with well-known time complexity classes.Comment: 18 pages, also available by (1) anonymous ftp at
ftp://ftp.fwi.uva.nl/pub/theory/illc/researchReports/CT-95-02.ps.gz ; (2) WWW
from http://www.fwi.uva.nl/~mtrautwe
Treebank-based acquisition of wide-coverage, probabilistic LFG resources: project overview, results and evaluation
This paper presents an overview of a project to acquire wide-coverage, probabilistic Lexical-Functional Grammar
(LFG) resources from treebanks. Our approach is based on an automatic annotation algorithm that annotates ârawâ treebank trees with LFG f-structure information approximating to basic predicate-argument/dependency structure. From the f-structure-annotated treebank
we extract probabilistic unification grammar resources. We present the annotation algorithm, the extraction of
lexical information and the acquisition of wide-coverage and robust PCFG-based LFG approximations including
long-distance dependency resolution.
We show how the methodology can be applied to multilingual, treebank-based unification grammar acquisition. Finally
we show how simple (quasi-)logical forms can be derived automatically from the f-structures generated for the treebank trees
A specification language for Lexical Functional Grammars
This paper defines a language L for specifying LFG grammars. This enables
constraints on LFG's composite ontology (c-structures synchronised with
f-structures) to be stated directly; no appeal to the LFG construction
algorithm is needed. We use L to specify schemata annotated rules and the LFG
uniqueness, completeness and coherence principles. Broader issues raised by
this work are noted and discussed.Comment: 6 pages, LaTeX uses eaclap.sty; Procs of Euro ACL-9
Multiple hierarchies : new aspects of an old solution
In this paper, we present the Multiple Annotation approach, which solves two problems: the problem of annotating overlapping structures, and the problem that occurs when documents should be annotated according to different, possibly heterogeneous tag sets. This approach has many advantages: it is based on XML, the modeling of alternative annotations is possible, each level can be viewed separately, and new levels can be added at any time. The files can be regarded as an interrelated unit, with the text serving as the implicit link. Two representations of the information contained in the multiple files (one in Prolog and one in XML) are described. These representations serve as a base for several applications
- âŠ