1. A method of executing computer instructions on at least one computing device in which the at least one computing device includes at least one processor and at least one memory, the method comprising: executing the computer instructions on the at least one processor of the at least one computing device; wherein the computer instructions to be executed comprise instructions for query processing; wherein the executing the query processing instructions comprise: representing a query as a numeral; comparing the query numeral with one or more numerals representing rooted partial subtrees of a complex tree hierarchy for a set of electronic documents; and storing the result of the comparison in the at least one memory of the at least one computing device; wherein the executing the query processing instructions further comprise: enumerating a set of rooted partial subtrees for the complex tree hierarchy, wherein the set of rooted partial subtrees comprises at least one rooted partial subtree having a same node as a second rooted partial subtree; determining one or more digital signals for numerals associated with the enumerated rooted partial subtrees of the set; and returning one or more corresponding rooted partial subtrees of the set based, at least in part, on the comparison.