Showing papers on "String (computer science) published in 2006"

Lightweight Directory Access Protocol (LDAP): Internationalized String Preparation

Abstract: The previous Lightweight Directory Access Protocol (LDAP) technical specifications did not precisely define how character string matching is to be performed. This led to a number of usability and interoperability problems. This document defines string preparation algorithms for character-based matching rules defined for use in LDAP. [STANDARDS-TRACK]

String method in collective variables: Minimum free energy paths and isocommittor surfaces

Abstract: A computational technique is proposed which combines the string method with a sampling technique to determine minimum free energy paths. The technique only requires to compute the mean force and another conditional expectation locally along the string, and therefore can be applied even if the number of collective variables kept in the free energy calculation is large. This is in contrast with other free energy sampling techniques which aim at mapping the full free energy landscape and whose cost increases exponentially with the number of collective variables kept in the free energy. Provided that the number of collective variables is large enough, the new technique captures the mechanism of transition in that it allows to determine the committor function for the reaction and, in particular, the transition state region. The new technique is illustrated on the example of alanine dipeptide, in which we compute the minimum free energy path for the isomerization transition using either two or four dihedral angles as collective variables. It is shown that the mechanism of transition can be captured using the four dihedral angles, but it cannot be captured using only two of them.

Tree-to-String Alignment Template for Statistical Machine Translation

Abstract: We present a novel translation model based on tree-to-string alignment template (TAT) which describes the alignment between a source parse tree and a target string. A TAT is capable of generating both terminals and non-terminals and performing reordering at both low and high levels. The model is linguistically syntax-based because TATs are extracted automatically from word-aligned, source side parsed parallel texts. To translate a source sentence, we first employ a parser to produce a source parse tree and then apply TATs to transform the tree into a target string. Our experiments show that the TAT-based model significantly outperforms Pharaoh, a state-of-the-art decoder for phrase-based models.

Algorithmic construction of sets for k-restrictions

Abstract: This work addresses k-restriction problems, which unify combinatorial problems of the following type: The goal is to construct a short list of strings in Σm that satisfies a given set of k-wise demands. For every k positions and every demand, there must be at least one string in the list that satisfies the demand at these positions. Problems of this form frequently arise in different fields in Computer Science.The standard approach for deterministically solving such problems is via almost k-wise independence or k-wise approximations for other distributions. We offer a generic algorithmic method that yields considerably smaller constructions. To this end, we generalize a previous work of Naor et al. [1995]. Among other results, we enhance the combinatorial objects in the heart of their method, called splitters, and construct multi-way splitters, using a new discrete version of the topological Necklace Splitting Theorem [Alon 1987].We utilize our methods to show improved constructions for group testing [Ngo and Du 2000] and generalized hashing [Alon et al. 2003], and an improved inapproximability result for SET-COVER under the assumption P ≠ NP.

Method and apparatus to control operation of a playback device

Abstract: Media metadata is accessible for a plurality of media items (See FIG. 12). The media metadata includes a number of strings to identify information regarding the media items (See FIG. 12). Phonetic metadata is associated the number of strings of the media metadata (See FIG. 12). Each portion of the phonetic metadata is stored in an original language of the string (See FIG. 12).

System and method for monitoring photovoltaic power generation systems

Abstract: A system and method for monitoring photovoltaic power generation systems or arrays (230), both on a local (site) level (100) and from a central location (610). The system includes panel and string combiner sentries (70) or intelligent devices, in bidirectional communication with a master device on the site to facilitate installation and troubleshooting of faults in the array (e.g., Fig. 9), including performance monitoring and diagnostic data collection (e.g., Figs. 14, 15).

Statistical syntax-directed translation with extended domain of locality

Abstract: In syntax-directed translation, the source-language input is first parsed into a parse-tree, which is then recursively converted into a string in the target-language. We model this conversion by an extended tree-to-string transducer that has multi-level trees on the source-side, which gives our system more expressive power and flexibility. We also define a direct probability model and use a linear-time dynamic programming algorithm to search for the best derivation. The model is then extended to the general log-linear frame-work in order to incorporate other features like n-gram language models. We devise a simple-yet-effective algorithm to generate non-duplicate k-best translations for n-gram rescoring. Preliminary experiments on English-to-Chinese translation show a significant improvement in terms of translation quality compared to a state-of-the- art phrase-based system.

Fast and Scalable Pattern Matching for Network Intrusion Detection Systems

Abstract: High-speed packet content inspection and filtering devices rely on a fast multipattern matching algorithm which is used to detect predefined keywords or signatures in the packets. Multipattern matching is known to require intensive memory accesses and is often a performance bottleneck. Hence, specialized hardware-accelerated algorithms are required for line-speed packet processing. We present hardware-implementable pattern matching algorithm for content filtering applications, which is scalable in terms of speed, the number of patterns and the pattern length. Our algorithm is based on a memory efficient multihashing data structure called Bloom filter. We use embedded on-chip memory blocks in field programmable gate array/very large scale integration chips to construct Bloom filters which can suppress a large fraction of memory accesses and speed up string matching. Based on this concept, we first present a simple algorithm which can scan for several thousand short (up to 16 bytes) patterns at multigigabit per second speeds with a moderately small amount of embedded memory and a few mega bytes of external memory. Furthermore, we modify this algorithm to be able to handle arbitrarily large strings at the cost of a little more on-chip memory. We demonstrate the merit of our algorithm through theoretical analysis and simulations performed on Snort's string set

Associating geographic-related information with objects

Abstract: Techniques for associating geographic-related information with objects are described. In one implementation, a search is conducted on a keyword string of one or more keywords descriptive or otherwise representative of a geographically-relevant object. If a location is identified, geographic-related semantic information of the location is associated with the geographically-relevant object. In some cases, multiple possible locations may be identified as a result of searching the keyword string. If multiple locations are identified, a probable location is determined and then geographic-related semantic information of the probable location is associated with the geographically-relevant object described by the keyword string.

System and method for finding desired results by incremental search using an ambiguous keypad with the input containing orthographic and typographic errors

Abstract: A system for finding and presenting content items in response to keystrokes entered by a user on an input device having a known layout of overloaded keys selected from a set of key layouts. The system includes (1) a database containing content items and terms characterizing the content items; (2) input logic for receiving keystrokes from the user and building a string corresponding to incremental entries by the user, each item in the string having the set of alphanumeric symbols associated with a corresponding keystroke; (3) mapping logic to map the string to the database to find the most likely content items corresponding to the incremental entries, the mapping logic operating in accordance with a defined error model corresponding to the known layout of overloaded keys; and (4) presentation logic for ordering the most likely content items identified by the mapping logic and for presenting the most likely content items.

High Speed Pattern Matching for Network IDS/IPS

Abstract: The phenomenal growth of the Internet in the last decade and society?s increasing dependence on it has brought along, a flood of security attacks on the networking and computing infrastructure. Intrusion detection/prevention systems provide defenses against these attacks by monitoring headers and payload of packets flowing through the network. Multiple string matching that can compare hundreds of string patterns simultaneously is a critical component of these systems, and is a well-studied problem. Most of the string matching solutions today are based on the classic Aho-Corasick algorithm, which has an inherent limitation; they can process only one input character in one cycle. As memory speed is not growing at the same pace as network speed, this limitation has become a bottleneck in the current network, having speeds of tens of gigabits per second. In this paper, we propose a novel multiple string matching algorithm that can process multiple characters at a time thus achieving multi-gigabit rate search speeds. We also propose an architecture for an efficient implementation on TCAM-based hardware. We additionally propose novel optimizations by making use of the properties of TCAMs to significantly reduce the memory requirements of the proposed algorithm. We finally present extensive simulation results of network-based virus/worm detection using real signature databases to illustrate the effectiveness of the proposed scheme.

Exploitation of language identification of media file data in speech dialog systems

Abstract: The present invention relates to a method for outputting a synthesized speech signal corresponding to an orthographic string stored in a media file comprising audio data, comprising the steps of analyzing the audio data to determine at least one candidate for a language of the orthographic string, estimating a phonetic representation of the orthographic string based on the determined at least one candidate for a language and synthesizing a speech signal based on the estimated phonetic representation of the orthographic string. The invention also relates to a media player incorporating such a method for a estimating phonetic representation for song and album titles as well as artists' names for speech recognition. Furthermore, the invention relates to the choice of an appropriate speech recognizer for automatically transcribing the lyrics of songs by using audio-based language estimates.

Round-optimal composable blind signatures in the common reference string model

Abstract: We build concurrently executable blind signatures schemes in the common reference string model, based on general complexity assumptions, and with optimal round complexity. Namely, each interactive signature generation requires the requesting user and the issuing bank to transmit only one message each. We also put forward the definition of universally composable blind signature schemes, and show how to extend our concurrently executable blind signature protocol to derive such universally composable schemes in the common reference string model under general assumptions. While this protocol then guarantees very strong security properties when executed within larger protocols, it still supports signature generation in two moves.

Multi-unit approach to text-to-speech synthesis

Abstract: Methods, apparatus, systems, and computer program products are provided for synthesizing speech. One method includes matching a first level of units of a received input string to audio segments from a plurality of audio segments including using properties of or between first level units to locate matching audio segments from a plurality of selections, parsing unmatched first level units into second level units, matching the second level units to audio segments using properties of or between the units to locate matching audio segments from a plurality of selections and synthesizing the input string, including combining the audio segments associated with the first and second units.

String matching method and system and computer-readable recording medium storing the string matching method

Abstract: A string matching method, system, and a computer-readable medium storing instructions for determining and obtaining a representative string for a plurality of strings that are written in various manners but share the same meaning. The string matching method includes: converting the input string into one or more second-language strings with reference to a language mapping table, which stores a plurality of pieces of mapping information for mapping a first-language string to a second-language string, and generating a conversion list; searching a representative list database, which storing a plurality of records each with a representative string and a corresponding second-language representative string, for records including the same second-language representative strings as the respective second-language strings in the conversion list and generating a candidate list; and determining a representative string from the candidate list to be an output representative string. Therefore, the string matching can provide string-based multimedia data classification scenarios.

Non-interactive correlation distillation, inhomogeneous Markov chains, and the reverse Bonami-Beckner inequality

Abstract: In this paper we studynon-interactive correlation distillation (NICD), a generalization of noise sensitivity previously considered in [5, 31, 39]. We extend the model toNICD on trees. In this model there is a fixed undirected tree with players at some of the nodes. One node is given a uniformly random string and this string is distributed throughout the network, with the edges of the tree acting as independent binary symmetric channels. The goal of the players is to agree on a shared random bit without communicating.

Efficient Realization of Coordinate Structures in Combinatory Categorial Grammar

Abstract: We describe a chart realization algorithm for Combinatory Categorial Grammar (CCG), and show how it can be used to efficiently realize a wide range of coordination phenomena, including argument cluster coordination and gapping. The algorithm incorporates three novel methods for improving the efficiency of chart realization: (i) using rules to chunk the input logical form into sub-problems to be solved independently prior to further combination; (ii) pruning edges from the chart based on the n-gram score of the edge’s string, in comparison to other edges with equivalent categories; and (iii) formulating the search as a best-first anytime algorithm, using n-gram scores to sort the edges on the agenda. The algorithm has been implemented as an extension to the OpenCCG open source CCG parser, and initial performance tests indicate that the realizer is fast enough for practical use in natural language dialogue systems.

Network distributed tracking wire transfer protocol

Abstract: A network distributed tracking wire transfer protocol for storing and retrieving data across a distributed data collection. The protocol includes a location string for specifying the network location of data associated with an entity in the distributed data collection, and an identification string for specifying the identity of an entity in the distributed data collection. According to the protocol, the length of the location string and the length of the identification string are variable, and an association between an identification string and a location string can be spontaneously and dynamically changed. The network distributed tracking wire transfer protocol is application independent, organizationally independent, and geographically independent. A method for using the protocol in a distributed data collection environment and a system for implementing the protocol are also provided.

Learning interpretable SVMs for biological sequence classification.

Abstract: Support Vector Machines (SVMs) – using a variety of string kernels – have been successfully applied to biological sequence classification problems. While SVMs achieve high classification accuracy they lack interpretability. In many applications, it does not suffice that an algorithm just detects a biological signal in the sequence, but it should also provide means to interpret its solution in order to gain biological insight. We propose novel and efficient algorithms for solving the so-called Support Vector Multiple Kernel Learning problem. The developed techniques can be used to understand the obtained support vector decision function in order to extract biologically relevant knowledge about the sequence analysis problem at hand. We apply the proposed methods to the task of acceptor splice site prediction and to the problem of recognizing alternatively spliced exons. Our algorithms compute sparse weightings of substring locations, highlighting which parts of the sequence are important for discrimination. The proposed method is able to deal with thousands of examples while combining hundreds of kernels within reasonable time, and reliably identifies a few statistically significant positions.

Discovering Frequent Closed Partial Orders from Strings

Abstract: Mining knowledge about ordering from sequence data is an important problem with many applications, such as bioinformatics, Web mining, network management, and intrusion detection. For example, if many customers follow a partial order in their purchases of a series of products, the partial order can be used to predict other related customers' future purchases and develop marketing campaigns. Moreover, some biological sequences (e.g., microarray data) can be clustered based on the partial orders shared by the sequences. Given a set of items, a total order of a subset of items can be represented as a string. A string database is a multiset of strings. In this paper, we identify a novel problem of mining frequent closed partial orders from strings. Frequent closed partial orders capture the nonredundant and interesting ordering information from string databases. Importantly, mining frequent closed partial orders can discover meaningful knowledge that cannot be disclosed by previous data mining techniques. However, the problem of mining frequent closed partial orders is challenging. To tackle the problem, we develop Frecpo (for frequent closed partial order), a practically efficient algorithm for mining the complete set of frequent closed partial orders from large string databases. Several interesting pruning techniques are devised to speed up the search. We report an extensive performance study on both real data sets and synthetic data sets to illustrate the effectiveness and the efficiency of our approach

Multi-language document search and retrieval system

Abstract: A multi-lingual indexing and search system performs tokenization and stemming in a manner which is independent of whether index entries and search terms appear as words in a dictionary. During the tokenization phase of the process, a string of text is separated into individual word tokens, and predetermined types of tokens are eliminated from further processing. The stemming phase of the process reduces words to grammatical stems by removing known word-endings associated with the various languages to be supported. Known word endings are removed from the word tokens without any effort to guarantee that the remaining stem is contained in a dictionary. In a preferred implementation, the stemming process is only applied to nouns.

Spelling-Error Tolerant, Order-Independent Pass-Phrases via the Damerau-Levenshtein String-Edit Distance Metric.

Abstract: It is well understood that passwords must be very long and complex to have sufficient entropy for security purposes. Unfortunately, these passwords tend to be hard to memorize, and so alternatives are sought. Smart Cards, Biometrics, and Reverse Turing Tests (human-only solvable puzzles) are options, but another option is to use pass-phrases. This paper explores methods for making passphrases suitable for use with password-based authentication and key-exchange (PAKE) protocols, and in particular, with schemes resilient to server-file compromise. In particular, the Ω-method of Gentry, MacKenzie and Ramzan, is combined with the Bellovin-Merritt protocol to provide mutual authentication (in the random oracle model (Canetti, Goldreich & Halevi 2004, Bellare, Boldyreva & Palacio 2004, Maurer, Renner & Holenstein 2004)). Furthermore, since common password-related problems are typographical errors, and the CAPSLOCK key, we show how a dictionary can be used with the DamerauLevenshtein string-edit distance metric to construct a case-insensitive pass-phrase system that can tolerate zero, one, or two spelling-errors per word, with no loss in security. Furthermore, we show that the system can be made to accept pass-phrases that have been arbitrarily reordered, with a security cost that can be calculated. While a pass-phrase space of 2 is not achieved by this scheme, sizes in the range of 2 to 2 result from various selections of parameter sizes. An attacker who has acquired the server-file must exhaust over this space, while an attacker without the serverfile cannot succeed with non-negligible probability.

PastryStrings: A Comprehensive Content-Based Publish/Subscribe DHT Network

Abstract: In this work we propose and develop a comprehensive infrastructure, coined PastryStrings, for supporting rich queries on both numerical (with range, and comparison predicates) and string attributes, (accommodating equality, prefix, suffix, and containment predicates) over DHT networks utilising prefix-based routing. As event-based, publish/ subscribe information systems are a champion application class, we formulate our solution in terms of this environment.

Search‐based software test data generation for string data using program‐specific search operators

Abstract: This paper presents a novel approach to automatic software test data generation, where the test data is intended to cover program branches which depend on string predicates such as string equality, string ordering and regular expression matching. A search-based approach is assumed and some potential search operators and corresponding evaluation functions are assembled. Their performance is assessed empirically by using them to generate test data for a number of test programs. A novel approach of using search operators based on programming language string operators and parameterized by string literals from the program under test is introduced. These operators are also assessed empirically in generating test data for the test programs and are shown to provide a significant increase in performance. Copyright © 2006 John Wiley & Sons, Ltd.

The number of runs in a string : Improved analysis of the linear upper bound

Abstract: A run (or a maximal repetition) in a string is an inclusion-maximal periodic segment in a string. Let p(n) be the maximal number of runs in a string of length n. It has been shown in [8] that p(n) = O(n), the proof was very complicated and the constant coefficient in O(n) has not been given explicitly. We propose a new approach to the analysis of runs based on the properties of subperiods: the periods of periodic parts of the runs. We show that p(n) < 5 n. Our proof is inspired by the results of [4], where the role of new periodicity lemmas has been emphasized.

Cache-oblivious string B-trees

Abstract: B-trees are the data structure of choice for maintaining searchable data on disk. However, B-trees perform suboptimally when keys are long or of variable length,when keys are compressed, even when using front compression, the standard B-tree compression scheme,for range queries, andwith respect to memory effects such as disk prefetching.This paper presents a cache-oblivious string B-tree (COSB-tree) data structure that is efficient in all these ways: The COSB-tree searches asymptotically optimally and inserts and deletes nearly optimally.It maintains an index whose size is proportional to the front-compressed size of the dictionary. Furthermore, unlike standard front-compressed strings, keys can be decompressed in a memory-efficient manner.It performs range queries with no extra disk seeks; in contrast, B-trees incur disk seeks when skipping from leaf block to leaf block.It utilizes all levels of a memory hierarchy efficiently and makes good use of disk locality by using cache-oblivious layout strategies.

Global grammar constraints

Abstract: Global constraints are an important tool in the constraint toolkit. Unfortunately, whilst it is usually easy to specify when a global constraint holds, it is often difficult to build a good propagator. One promising direction is to specify global constraints via grammars or automata. For example, the Regular constraint [1] permits us to specify a wide range of global constraints by means of a DFA accepting a regular language, and to propagate this constraint specification efficiently and effectively. More precisely, the Regular constraint ensures that the values taken by a sequence of variables form a string accepted by the DFA. In this paper, we consider how to propagate such grammar constraints and a number of extensions.

Natural language search system

Abstract: A natural language system searching system develops concept and string indexes of a textual database, such as a group of litigation documents, by breaking the text to be indexed into sentences, words, dates, names and places in a reader, identifying phrases in a phrase parser, recovering word stems in a morphology module and determining the sense of potentially ambiguous words in a sense selector, all in accordance with words and concepts (word senses) stored in lexicon database 9-32. A query may then be processed by the reader, phrase parser, morphology module, and sense selector to provide a text meaning output which can be compared with the concept and string indexes to identify, retrieve and display documents and/or portions of documents related to the query. A lexicon enhancer adds vocabulary semi-automatically.

Operating non-volatile memory with boost structures

Abstract: A method for operating non-volatile memory having boost structures. The boost structures are provided for individual NAND strings and can be individually controlled to assist in programming, verifying and reading processes. The boost structures can be commonly boosted and individually discharged, in part, based on a target programming state or verify level. The boost structures assists in programming so that the programming and pass voltage on a word line can be reduced, thereby reducing side effects such as program disturb. During verifying, all storage elements on a word line can be verified concurrently. The boost structure can also assist during reading. In one approach, the NAND string has dual source-side select gates between which the boost structure contacts the substrate at a source/drain region, and a boost voltage is provided to the boost structure via a source-side of the NAND string.