Scientific publications

The major advantage of the n-gram inverted index is the possibility to locate any given substring in a document collection. Nevertheless, the n-gram inverted index also has drawbacks: If the collections are getting bigger, this index tends to be very large and the performance drops significantly. We propose a novel technique of enhancing the performance of an n-gram inverted index with the use of additional fingerprints for each n-gram. A fingerprint contains information about the positions of an n-gram. When combining two or more n-grams, these fingerprints also provide information about the positions of the combination. This can be used to reduce the complexity of merging the n-gram postings lists for a given search and improves the performance of the n-gram inverted index. Furthermore it is possible to freely scale the size of the fingerprints in order to adjust the performance of the index. The size of a fingerprint is neither dependent of the size of the document collection nor the number of n-grams.