29. The method according to claim 1 , wherein there are groupings of data rows and each collection of values contains the values of a single data attribute for a single grouping of data rows, ordinal numbers of values in the collection of values being equal to ordinal numbers of rows in the corresponding grouping of data rows, and collections of values corresponding to the same data attribute being assigned to the same structure dictionary.
29. The method according to claim 1 , wherein there are groupings of data rows and each collection of values contains the values of a single data attribute for a single grouping of data rows, ordinal numbers of values in the collection of values being equal to ordinal numbers of rows in the corresponding grouping of data rows, and collections of values corresponding to the same data attribute being assigned to the same structure dictionary. 35. The method of claim 29 , wherein, for a data attribute assigned to a structure dictionary, each collection of values corresponding to the data attribute is assigned by a decomposition rule with a subset of structures in the structure dictionary, by: providing a first interface to a user of the system, the user interacting with said first interface to define and add new structures to the structure dictionary; providing a second interface to a user of the system, the user interacting with said second interface to change the decomposition rule to be used for new collections of values corresponding to the data attribute; storing information about the current and all previous decomposition rules together with information about which collections of values correspond to each of the decomposition rules; and for each collection of values, composing its storage according to the subset of structures that the decomposition rule assigns to the corresponding collection of values.