[2] If all edit operations have the same unit costs (WC = WD = WI = 1) the problem is the same as computing the Levenshtein distance of two strings.
Several algorithms exist to provide an efficient way to determine string distance and specify the minimum number of transformation operations required.
[3][4] Such algorithms are particularly useful for delta creation operations where something is stored as a set of differences relative to a base version.
The extended variant of the problem includes a new type of edit operation: swapping any two adjacent symbols, with a cost of WS.
In particular, he proved that when WI < WC = WD = ∞ and 0 < WS < ∞ (or equivalently, changing and deletion are not permitted), the problem is NP-complete.