25. The method according to claim 14 , wherein the word belonging to the structure dictionary is modifiable and methods of modifying the word include at least one of: detecting symbols in the word that can be replaced by more detailed sub-words, automatically adding new words obtained by replacing the symbols in the structure dictionary by the sub-words, or recommending the new word to a user of the relational database system via an interface, the user deciding whether to add the new word to structure dictionary and whether to replace the word with the new word in the structure dictionary; evaluating the candidate replacements of symbols by more detailed sub-words based on a group of criteria including at least one of minimizing the number of structure sub-collections and minimizing the cost of storing symbol sub-collections; and providing an interface to a user of the relational database system, the interface reporting amounts of values matched by new words obtained by replacing symbols by more detailed sub-words and sizes of symbol sub-collections corresponding to symbols of the more detailed sub-words, the user using the interface to add the new words to the structure dictionary and to remove the word from the structure dictionary.
25. The method according to claim 14 , wherein the word belonging to the structure dictionary is modifiable and methods of modifying the word include at least one of: detecting symbols in the word that can be replaced by more detailed sub-words, automatically adding new words obtained by replacing the symbols in the structure dictionary by the sub-words, or recommending the new word to a user of the relational database system via an interface, the user deciding whether to add the new word to structure dictionary and whether to replace the word with the new word in the structure dictionary; evaluating the candidate replacements of symbols by more detailed sub-words based on a group of criteria including at least one of minimizing the number of structure sub-collections and minimizing the cost of storing symbol sub-collections; and providing an interface to a user of the relational database system, the interface reporting amounts of values matched by new words obtained by replacing symbols by more detailed sub-words and sizes of symbol sub-collections corresponding to symbols of the more detailed sub-words, the user using the interface to add the new words to the structure dictionary and to remove the word from the structure dictionary. 26. The method of claim 25 , wherein the evaluating is based on heuristic optimization, including at least one of: greedy, randomized, and Al-based algorithms.