Efficient retrieval of variable-length character string data

Inactive Publication Date: 2005-06-02
NEC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] Accordingly, an object of the present invention is to provide an information retrieval technique, which ach

Problems solved by technology

On the other hand, a pattern that does not match leading characters of the retrieval key, such as a pattern “BCDE”, does not meet a condition of prefix matching, even if the pattern is a partial character string of the retrieval key.
Such a prior art has a disadvantage, which will be described with reference to FIG. 1.
Therefore, if a character string starting with “PQRSPQRSP” is inputted as a retrieval key, the narrowing of the patterns1305 to 1

Method used

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  • Efficient retrieval of variable-length character string data
  • Efficient retrieval of variable-length character string data
  • Efficient retrieval of variable-length character string data

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

1. First Embodiment

[0044] 1.1) Configuration

[0045] Referring to FIG. 2, a variable-length character string retrieval apparatus 1 according to a first embodiment of the present invention generally includes a pattern registration section 131, a retrieval execution section 11 and a pattern storage section 12.

[0046] When a registration pattern 132 is inputted, the pattern registration section 131 extracts N prefixes (N: natural number) with different lengths in accordance with a given extraction rule. Further, the pattern registration section 131 selects one prefix among the extracted prefixes in accordance with a given selection rule, and sets the selected prefix as an index element for the registration pattern 132. Thereafter, a predetermined hash function is applied to the prefix set as the index element to obtain a hash value, and this prefix is registered on a prefix pattern list 121 in the pattern storage section 12, at a location according to the obtained hash value. That is, i...

second embodiment

2. Second Embodiment

[0075] In the first embodiment as described above, the prefix extractor 111 extracts prefixes with predetermined N different lengths from a retrieval key, and the pattern registration section 131 extracts a prefix to be set as an index element from a registration pattern based on the predetermined N different lengths. By comparison, in a second embodiment of the present invention, the prefix extractor 111 extracts prefixes with N different lengths according to a predetermined separating character, and the pattern registration section 131 extracts a prefix to be set as an index element from a registration pattern according to the predetermined separating character.

[0076] 2.1) Prefix Extraction

[0077] First, the operation of the prefix extractor 111 in the second embodiment will be described with reference to FIGS. 6 and 7. In the following description, it is assumed that N=4. In addition, consideration will be given to a case, for example, where a retrieval key 5...

third embodiment

3. Third Embodiment

[0092] In the first and second embodiments, the retrieval of the longest prefix match of a variable-length character string is performed. By comparison, in a third embodiment of the present invention, the retrieval of a longest suffix match will be performed. Now the third embodiment will be described with reference to FIGS. 11 and 12.

[0093]FIG. 11 is a block diagram showing an exemplary configuration of a variable-length character string retrieval apparatus 1a for retrieving a longest suffix match. Referring to FIG. 11, the variable-length character string retrieval apparatus 1a according to the third embodiment generally includes a pattern registration section 131a, a retrieval execution section 11a and a pattern storage section 12a.

[0094] When a registration pattern 132 is inputted, the pattern registration section 131a extracts N suffixes (N: natural number) with different lengths from the tail of the registration pattern 132 in accordance with a given extra...

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PUM

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Abstract

Prefixes are registered on a first list as index elements for respective registration patterns. Each prefix is selected as the longest of different-length prefixes that are extractable from a registration pattern in accordance with an extraction rule. Suffixes, which are the remaining parts of the registration patterns excluding the respective prefixes, are registered on a second list. Using different-length prefixes that are extracted from a retrieval key in accordance with the extraction rule, a prefix retriever searches the first list to retrieve a registration pattern whose prefix matches any of the prefixes of the retrieval key. A suffix checker carries out a check on the suffix of the registration pattern retrieved by the prefix retriever, among the suffixes on the second list, as to whether the suffix of the registration pattern matches the suffix of the retrieval key.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an information retrieval technology of retrieving variable-length character string data. More particularly, the present invention relates to a technology to enhance efficiency in retrieving the longest prefix match or longest suffix match of a variable-length character string. [0003] 2. Description of the Related Art [0004] First of all, a description will be given of a general outline of the retrieval of the longest prefix match; which is the primary application target of the present invention. In the retrieval of the longest prefix match, a retrieval result is, in a pattern list, the longest of patterns that match leading characters of a retrieval key (character string to retrieve). For example, when there are three patterns “ABCD”, “ABCDEFGH” and “ABCDE” that match leading characters of a retrieval key (e.g., “ABCDEFGHIJ”), the longest matching pattern “ABCDEFGH” is outputted as a...

Claims

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Application Information

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IPC IPC(8): G06F17/30
CPCG06F17/30985G06F16/90344Y10S707/99936
Inventor MOTOKI, AKIHIRO
Owner NEC CORP
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