1. A method for changing a pattern in data according to at least one data model (DM 1 , DM 2 ), said data being grouped in a data base DDE) according to entity, the method being performed in a pattern processing node ( 21 ) of a data collection system ( 10 ) and comprising the steps of: obtaining ( 66 ) an existing pattern (P 1 ) of historical data according to at least one existing data model (DM 1 ), said existing pattern relating to an entity ( 11 ) associated with the data collection system, obtaining ( 68 ) a further pattern (P 2 ) of newer data according to a further data model (DM 2 ), said further pattern also relating to said entity, comparing ( 70 ) the above patterns with each other, determining ( 72 ) if the existing data model can be mapped on the further data model based on the comparison, and updating ( 76 ) the existing pattern with the further pattern in relation to the historical data if the existing data model can be mapped on the further data model.