Search system and method for retrieval of data, and the use thereof in a search engine
First Claim
1. A search system for information retrieval, particularly information stored in form of text, wherein a text T comprises words and/or symbols s and sequences S thereof, wherein the information retrieval takes place with a given or varying degree of matching between a query Q, wherein the query Q comprises words and/or symbols q and sequences thereof P, and retrieved information R comprising words and/or symbols and sequences thereof from the text T, wherein the search system comprises a data structure for storing at least a part of the text T, and a metric M which measures the degree of matching between the query Q and retrieved information R, and wherein the search system implements search algorithms for executing a search, particularly a full text search on the basis of keywords kw, characterized in that the data structure comprises a tree structure in the form of a non-evenly spaced sparse suffix tree ST(T) for storing suffixes of words and/or symbols s and sequences S thereof in the text T, that the metric M comprises a combination of an edit distance metric D(s,q) for an approximate degree of matching between words and/or symbols s;
- q in respectively the text T and a query Q and an edit distance metric Dws(S,P) for an approximate degree of matching between sequences S of words and/or symbols s in the text T and a query sequence P of words and/or symbols q in the query Q, the latter edit distance metric including weighting cost functions for edit operations which transform sequences of words and/or symbols s in the text T into the sequence P of words and/or symbols q in the query Q, the weighting taking place with a value proportional to a change in the length of the sequence S upon a transformation or dependent on the size of the words and/or symbols s;
q in sequences S;
P to be matched, that the implemented search algorithms comprise a first algorithm for determining the degree of matching between words and/or symbols s;
q in the suffix tree representation of respectively the text T and a query Q, and a second algorithm for determining the degree of matching between sequences S;
P of words and/or symbols s;
q in the suffix tree representation of respectively the text T and the query Q, said first and/or second algorithms searching the data structure with queries Q in the form of either words, symbols, sequences of words or sequences of symbols or combinations thereof, such that information R is retrieved on the basis of query Q with a specified degree of matching between the former and the latter, and that the search algorithms optionally also comprise a third algorithm for determining exact matching between words and/or symbols s;
q in the suffix tree representation of respectively the text T and the query Q and/or a fourth algorithm for determining exact matching between sequences S;
P of words and/or symbols s;
q in the suffix tree representation of respectively the text T and the query Q, said third and/or fourth algorithms searching the data structure with queries Q in the form of either words, symbols, sequences of words, or sequences of symbols or combinations thereof, such that information R is retrieved on the basis of the query Q with an exact matching between the former and the latter.
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Abstract
A search system for information retrieval includes a data structure in the form of a non-evenly spaced sparse suffix tree for storing suffixes of words and/or symbols, or sequences thereof, in a text T, a metric M including combined edit distance metrics for an approximate degree of matching respectively between words and/or symbols, or between sequences thereof, in the text T and a query Q, the latter distance metric including weighting cost functions for edit operations which transform a sequence S of the text into a sequence P of the query Q, and search algorithms for determining the degree of matching respectively between words and/or symbols, or between sequences thereof, in respectively the text T and the query Q, such that information R is retrieved with a specified degree of matching with the query Q. Optionally the search system also includes algorithms for determining exact matching such that information R may be retrieved with an exact degree of matching with the query Q.
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Citations
14 Claims
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1. A search system for information retrieval, particularly information stored in form of text, wherein a text T comprises words and/or symbols s and sequences S thereof, wherein the information retrieval takes place with a given or varying degree of matching between a query Q, wherein the query Q comprises words and/or symbols q and sequences thereof P, and retrieved information R comprising words and/or symbols and sequences thereof from the text T, wherein the search system comprises a data structure for storing at least a part of the text T, and a metric M which measures the degree of matching between the query Q and retrieved information R, and wherein the search system implements search algorithms for executing a search, particularly a full text search on the basis of keywords kw, characterized in that the data structure comprises a tree structure in the form of a non-evenly spaced sparse suffix tree ST(T) for storing suffixes of words and/or symbols s and sequences S thereof in the text T, that the metric M comprises a combination of an edit distance metric D(s,q) for an approximate degree of matching between words and/or symbols s;
- q in respectively the text T and a query Q and an edit distance metric Dws(S,P) for an approximate degree of matching between sequences S of words and/or symbols s in the text T and a query sequence P of words and/or symbols q in the query Q, the latter edit distance metric including weighting cost functions for edit operations which transform sequences of words and/or symbols s in the text T into the sequence P of words and/or symbols q in the query Q, the weighting taking place with a value proportional to a change in the length of the sequence S upon a transformation or dependent on the size of the words and/or symbols s;
q in sequences S;
P to be matched, that the implemented search algorithms comprise a first algorithm for determining the degree of matching between words and/or symbols s;
q in the suffix tree representation of respectively the text T and a query Q, and a second algorithm for determining the degree of matching between sequences S;
P of words and/or symbols s;
q in the suffix tree representation of respectively the text T and the query Q, said first and/or second algorithms searching the data structure with queries Q in the form of either words, symbols, sequences of words or sequences of symbols or combinations thereof, such that information R is retrieved on the basis of query Q with a specified degree of matching between the former and the latter, and that the search algorithms optionally also comprise a third algorithm for determining exact matching between words and/or symbols s;
q in the suffix tree representation of respectively the text T and the query Q and/or a fourth algorithm for determining exact matching between sequences S;
P of words and/or symbols s;
q in the suffix tree representation of respectively the text T and the query Q, said third and/or fourth algorithms searching the data structure with queries Q in the form of either words, symbols, sequences of words, or sequences of symbols or combinations thereof, such that information R is retrieved on the basis of the query Q with an exact matching between the former and the latter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- q in respectively the text T and a query Q and an edit distance metric Dws(S,P) for an approximate degree of matching between sequences S of words and/or symbols s in the text T and a query sequence P of words and/or symbols q in the query Q, the latter edit distance metric including weighting cost functions for edit operations which transform sequences of words and/or symbols s in the text T into the sequence P of words and/or symbols q in the query Q, the weighting taking place with a value proportional to a change in the length of the sequence S upon a transformation or dependent on the size of the words and/or symbols s;
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10. A method in a search system for information retrieval, particularly information stored in form of text, wherein a text T comprises words and/or symbols s and sequences S thereof, wherein the information retrieval takes place with a given or varying degree of matching between a query Q, wherein the query Q comprises words and/or symbols q and sequences P thereof, and retrieved information R comprising words and/or symbols and sequences thereof from the text T, wherein the search system comprises a data structure for storing at least a part of the text T, and a metric M which measures the degree of matching between the query Q and retrieved information R, and wherein the search system implements search algorithms for executing a search, particularly a full text search on the basis of keywords kw, wherein the information in the text T is divided into words s and word sequences S, the words being substrings of the entire text separated by word boundary terms and forming a sequence of symbols, and wherein each word is structured as a sequence of symbols, characterized by generating the data structure as a word-spaced sparse suffix tree SSTws(T) of a text T for representing all the suffixes starting at a word separator symbol in the text T, storing sequence information of the words s in the text T in the word-spaced sparse suffix tree SSTws(T), generating a combined edit distance metric M comprising an edit distance metric D(s,q) for words s in the text T and a query word q in a query Q and a word-size dependent edit distance metric Dws(S,P) for sequences S of words s in the text T and a sequence P of words q in the query Q, the edit distance metric Dws(S,P) being the minimum sum of costs for edit operations transforming a sequence S into the sequence P, the minimum sum of costs being the minimum sum of cost functions for each edit operation weighted by a value proportional to the change in the total length of the sequence S or by the ratio of the current word length and average word length in the sequences S;
- P, and determining the degree of matching between words s,q by calculating the edit distance D(s,q) between the words s of the retrieved information R and the word q of a query Q, or in case the words s,q are more than k errors from each other, determining the degree of matching between the word sequences SR;
PQ of retrieved information R and a query Q respectively by calculating the edit distance Dws(SR,PQ) for all matches. - View Dependent Claims (11, 12, 13, 14)
- P, and determining the degree of matching between words s,q by calculating the edit distance D(s,q) between the words s of the retrieved information R and the word q of a query Q, or in case the words s,q are more than k errors from each other, determining the degree of matching between the word sequences SR;
Specification