content of the offers for determination of similarity any kind of clustering algorithm may be used such as the fast isodata algorithm nargess memarsadeghi david m mount nathan s netanyahu and jacqueline le moigne u2014 a fast implementation of the isodata clustering algorithm international journal of computational geometry amp applications 2007 pp 71 103 or the k means algorithm coates adam ng andrew y u2014 learning feature representations with k means neural networks tricks of the trade reloaded springer lncs 2012 after all of the offers have been automatically clustered and each offer is assigned to a respective one of the virtual items within its category the thus obtained clusters of the virtual items are stored into the database and can be used as a reference classification for the pattern learning procedure of the next steps for example the distance between two word vectors a and b is computed as follows 1 for each relevant word in word vector a the same relevant word in the word vector b is searched within a predefined length difference 2 for each pairs of the previously found common relevant words we compute the edit distance between the two words in this context the term u201c edit distance.