1. A method of managing metadata in a relational database system using a processor, the metadata created in a form of rough values corresponding to collections of values, each rough value being substantially smaller than the corresponding collection of values, the method comprising: assigning a collection of values to a structure dictionary, wherein each of the values represents the value of a row for an attribute and has a unique ordinal number within the collection, and wherein the structure dictionary contains structures defined based on at least one of interaction with a user of the system via an interface, automatic detection of structures occurring in data, and predetermined information about structures relevant to data content that is stored in the system; forming match granules; gathering information about how values match the structures in the structure dictionary; for each structure in the structure dictionary, forming structure granules; gathering information about the values in the collection that match the structure; and forming a rough value out of the match granules and the structure granules.