PAT Tree Research Articles

Research and Application of Network Technology and Online Translation Tools in English Translation

This paper proposed a novel method to extract bilingual translation pairs from the web. Based on the observation that translation pairs tend to appear collectively on the web, a recursive process is used to extract high quality translation pairs from the web. First query the search engine with some seed data and crawl the returned pages. Then identify the Collective Translation Pair Block (CTPB) which contains the collective translation pairs using a heuristic evaluation method. After the CTPB has been identified, a PAT tree is employed to generate the extraction patterns automatically. Then a ranking SVM model is used to re-rank these patterns based on the F measure. The top 10 patterns are adopted to extract the translation pairs with the help of surface pattern. At last in order to get the high quality extraction translation, the extracted translation pairs are verified by a SVM classifier based on the translation relevant between the source and the target language.

A hierarchical model of a FTP search engine with applications

Because the traditional FTP search engines usually adopt centralised spiders to collect data, insufficient temporal effectiveness is their major demerit. For solving this problem, this paper presents an efficient hierarchical FTP search engine model that deploys the spider agent on the node host of some specific network for collecting file data of FTP servers. The key technologies involve a regional responsibility mechanism, a search mechanism based on the asynchronous retrieval technology and a PAT Tree storage mechanism. The simulation shows that the responding time is less than that of the traditional system and the temporal effectiveness arrives at the application level. In addition, the test results show that the architecture has a good scalability.

A dynamic construction algorithm for the Compact Patricia trie using the hierarchical structure

We need to access objective information efficiently and arbitrary strings in the text at high speed. In several key retrieval strategies, we often use the binary trie for supporting fast access method in order. Especially, the Patricia trie (Pat tree) is famous as the fastest access method in binary tries, because it has the shallowest tree structure. However, the Pat tree requires many good physician storage spaces in memory, if key set registered is large. Thereby, an expense problem happens when storing this trie to the main storage unit. We already proposed a method that use compact bit stream and compress a Pat tree to solve this problem. This is called Compact Patricia trie (CPat tree). This CPat tree needs capacity of only a very few memory device. However, if a size of key set increases, the time expense that search, update key increases gradually. This paper proposes a new structure of the CPat tree to avoid that it takes much time in search and update about much key set, and a method to construct a new CPat tree dynamically and efficiently. This method divides a CPat tree consisting of bit string to fixed depth. In addition, it compose been divided CPAT tree hierarchically. A construction algorithm that proves this update time requires alteration of only one tree among whole trees that is divided. From experimental result that use 120,000 English substantives and 70,000 Japanese substantives, we prove an update time that is faster more than 40 times than the traditional method. Moreover, a space efficiency of memory increases about 35% only than the traditional method.

A survey of alternative designs for a search engine storage structure

Three information retrieval storage structures are considered to determine their suitability for a World Wide Web search engine: The Wolverhampton Web Library — The Next Generation. The structures are an inverted file, signature file and Pat tree. A number of implementations are considered for each structure. For the index of an inverted file a sorted array, B-tree, B+-tree, trie and hash table are considered. For the signature file vertical and horizontal partitioning schemes are considered and for the Pat tree a tree and array implementation are considered. A theoretical comparison of the structures is done on seven criteria that include: response time, support for results ranking, search techniques, file maintenance, efficient use of disk space (including the use of compression), scalability and extensibility. The comparison reveals that an inverted file is the most suitable structure, unlike the signature file and Pat tree, which encounter problems with very large corpora.

On the Construction of Classes of Suffix Trees for Square Matrices: Algorithms and Applications

We provide a uniform framework for the study of index data structures for a two-dimensional matrixTEXT[1:n, 1:n] whose entries are drawn from an ordered alphabetΣ. An index forTEXTcan be informally seen as the two-dimensional analog of the suffix tree for a string. It allows on-line searches and statistics to be performed onTEXTby representing compactly theΘ(n3) square submatrices ofTEXTin optimalO(n2) space. We identify 4n−1families of indices forTEXT, each containing ∏ni=1 (2i−1)! isomorphic data structures. We also develop techniques leading to a single algorithm that efficiently builds any index in any family inO(n2 log n) time andO(n2) space. Such an algorithm improves in various respects the algorithms for the construction of the PAT tree and the Lsuffix tree. The framework and the algorithm easily generalize tod>2 dimensions. Moreover, as part of our algorithm, we provide new algorithmic tools that yield a space-efficient implementation of the “naming scheme” of R. Karpet al.(in“Proceedings, Fourth Symposium on Theory of Computing,” pp. 125–136) for strings and matrices.