document: Detecting the origin of text segments efficiently In the origin detection problem an algorithm is given a set S of documents , ordered by creation time , and a query document D. It needs to output for every consecutive sequence of k alphanumeric terms in D the earliest document in $ S$ in which the sequence appeared ( if such a document exists ) . Algorithms for the origin detection problem can , for example , be used to detect the `` origin '' of text segments in D and thus to detect novel content in D. They can also find the document from which the author of D has copied the most ( or show that D is mostly original . ) We concentrate on solutions that use only a fixed amount of memory . We propose novel algorithms for this problem and evaluate them together with a large number of previously published algorithms . Our results show that ( 1 ) detecting the origin of text segments efficiently can be done with very high accuracy even when the space used is less than 1 % of the size of the documents in $ S$ , ( 2 ) the precision degrades smoothly with the amount of available space , ( 3 ) various estimation techniques can be used to increase the performance of the algorithms .
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