11,392 research outputs found
Principles and Implementation of Deductive Parsing
We present a system for generating parsers based directly on the metaphor of
parsing as deduction. Parsing algorithms can be represented directly as
deduction systems, and a single deduction engine can interpret such deduction
systems so as to implement the corresponding parser. The method generalizes
easily to parsers for augmented phrase structure formalisms, such as
definite-clause grammars and other logic grammar formalisms, and has been used
for rapid prototyping of parsing algorithms for a variety of formalisms
including variants of tree-adjoining grammars, categorial grammars, and
lexicalized context-free grammars.Comment: 69 pages, includes full Prolog cod
Efficient Analysis of Complex Diagrams using Constraint-Based Parsing
This paper describes substantial advances in the analysis (parsing) of
diagrams using constraint grammars. The addition of set types to the grammar
and spatial indexing of the data make it possible to efficiently parse real
diagrams of substantial complexity. The system is probably the first to
demonstrate efficient diagram parsing using grammars that easily be retargeted
to other domains. The work assumes that the diagrams are available as a flat
collection of graphics primitives: lines, polygons, circles, Bezier curves and
text. This is appropriate for future electronic documents or for vectorized
diagrams converted from scanned images. The classes of diagrams that we have
analyzed include x,y data graphs and genetic diagrams drawn from the biological
literature, as well as finite state automata diagrams (states and arcs). As an
example, parsing a four-part data graph composed of 133 primitives required 35
sec using Macintosh Common Lisp on a Macintosh Quadra 700.Comment: 9 pages, Postscript, no fonts, compressed, uuencoded. Composed in
MSWord 5.1a for the Mac. To appear in ICDAR '95. Other versions at
ftp://ftp.ccs.neu.edu/pub/people/futrell
siEDM: an efficient string index and search algorithm for edit distance with moves
Although several self-indexes for highly repetitive text collections exist,
developing an index and search algorithm with editing operations remains a
challenge. Edit distance with moves (EDM) is a string-to-string distance
measure that includes substring moves in addition to ordinal editing operations
to turn one string into another. Although the problem of computing EDM is
intractable, it has a wide range of potential applications, especially in
approximate string retrieval. Despite the importance of computing EDM, there
has been no efficient method for indexing and searching large text collections
based on the EDM measure. We propose the first algorithm, named string index
for edit distance with moves (siEDM), for indexing and searching strings with
EDM. The siEDM algorithm builds an index structure by leveraging the idea
behind the edit sensitive parsing (ESP), an efficient algorithm enabling
approximately computing EDM with guarantees of upper and lower bounds for the
exact EDM. siEDM efficiently prunes the space for searching query strings by
the proposed method, which enables fast query searches with the same guarantee
as ESP. We experimentally tested the ability of siEDM to index and search
strings on benchmark datasets, and we showed siEDM's efficiency.Comment: 23 page
Non-hierarchical Structures: How to Model and Index Overlaps?
Overlap is a common phenomenon seen when structural components of a digital
object are neither disjoint nor nested inside each other. Overlapping
components resist reduction to a structural hierarchy, and tree-based indexing
and query processing techniques cannot be used for them. Our solution to this
data modeling problem is TGSA (Tree-like Graph for Structural Annotations), a
novel extension of the XML data model for non-hierarchical structures. We
introduce an algorithm for constructing TGSA from annotated documents; the
algorithm can efficiently process non-hierarchical structures and is associated
with formal proofs, ensuring that transformation of the document to the data
model is valid. To enable high performance query analysis in large data
repositories, we further introduce an extension of XML pre-post indexing for
non-hierarchical structures, which can process both reachability and
overlapping relationships.Comment: The paper has been accepted at the Balisage 2014 conferenc
Improved ESP-index: a practical self-index for highly repetitive texts
While several self-indexes for highly repetitive texts exist, developing a
practical self-index applicable to real world repetitive texts remains a
challenge. ESP-index is a grammar-based self-index on the notion of
edit-sensitive parsing (ESP), an efficient parsing algorithm that guarantees
upper bounds of parsing discrepancies between different appearances of the same
subtexts in a text. Although ESP-index performs efficient top-down searches of
query texts, it has a serious issue on binary searches for finding appearances
of variables for a query text, which resulted in slowing down the query
searches. We present an improved ESP-index (ESP-index-I) by leveraging the idea
behind succinct data structures for large alphabets. While ESP-index-I keeps
the same types of efficiencies as ESP-index about the top-down searches, it
avoid the binary searches using fast rank/select operations. We experimentally
test ESP-index-I on the ability to search query texts and extract subtexts from
real world repetitive texts on a large-scale, and we show that ESP-index-I
performs better that other possible approaches.Comment: This is the full version of a proceeding accepted to the 11th
International Symposium on Experimental Algorithms (SEA2014
Advanced content-based semantic scene analysis and information retrieval: the SCHEMA project
The aim of the SCHEMA Network of Excellence is to bring together a critical mass of universities, research centers, industrial partners and end users, in order to design a reference system for content-based semantic scene analysis, interpretation and understanding. Relevant research areas include: content-based multimedia analysis and automatic annotation of semantic multimedia content, combined textual and multimedia information retrieval, semantic -web, MPEG-7 and MPEG-21 standards, user interfaces and human factors. In this paper, recent advances in content-based analysis, indexing and retrieval of digital media within the SCHEMA Network are presented. These advances will be integrated in the SCHEMA module-based, expandable reference system
Lightweight Lempel-Ziv Parsing
We introduce a new approach to LZ77 factorization that uses O(n/d) words of
working space and O(dn) time for any d >= 1 (for polylogarithmic alphabet
sizes). We also describe carefully engineered implementations of alternative
approaches to lightweight LZ77 factorization. Extensive experiments show that
the new algorithm is superior in most cases, particularly at the lowest memory
levels and for highly repetitive data. As a part of the algorithm, we describe
new methods for computing matching statistics which may be of independent
interest.Comment: 12 page
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