1. A method of defining relations between sub-bands of a sequence of wavelet transforms applied to an original n-dimensional signal, comprising: a. defining a list of sub-bands initially containing the original n-dimensional signal with a null label; b. repeatedly: (1) removing any sub-band with its label from said list of sub-bands; (2) creating a new low sub-band and a new high sub-band by respectively applying a pair of a low-pass and a high-pass 1D(1-dimensional) wavelet filters to said removed sub-band in the direction of dimension k of said sub-band's n dimensions; (3) defining a label for the new low sub-band as the removed sub-band's label concatenated with the symbol Lk, and a label for the new high sub-band as the removed sub-band's label concatenated with the symbol Hk; (4) inserting said two newly created low and high sub-bands, with their labels, to the list of sub-bands; c. defining the phase-space information of a given sub-band as the number and direction of symbols “Hk” appearing in the sub-band's label; d. partitioning the sub-bands of the list into groups of equal phase-space sub-bands; and e. defining a DAG (Directed Acyclic Graph) data structure comprising DAG relations between the sub-bands in each group.