A method for the definition of data categories is described. The method uses logic templates and may be used in database processing. One embodiment of the method comprises: selecting a plurality of attributes from a group of attributes, each attribute describing a possible data item in a set of data; selecting a logic template from a group of logic templates, each logic template comprising a predetermined logic expression containing one or more variables; and assigning one or more selected attributes to each variable within the selected the logic template to produce a logic expression defining the data category. A computer program product and a user interface for achieving this method are also described.