- 5 - Simple keyword representation has its problems –in particular when automatically extracted as not every word has similar importance longer documents have a higher chance to have an overlap with the user profile Standard measure: TF-IDF –Encodes text documents in multi-dimensional Euclidian space weighted term vector –TF: Measures, how often a term appears (density in a document) assuming that important terms appear more often normalization has to be done in order to take document length into account –IDF: Aims to reduce the weight of terms that appear in all documents
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