Pattern matching in pseudo real-time

It has recently been shown how to construct online, non-amortised approximate pattern matching algorithms for a class of problems whose distance functions can be classified as being local. Informally, a distance function is said to be local if for a pattern P of length m and any substring T[i,i+m-1] of a text T, the distance between P and T[i,i+m-1] can be expressed as @?"j@D(P[j],T[i+j]), where @D is any distance function between individual characters. We show in this work how to tackle online approximate matching when the distance function is non-local. We give new solutions which are applicable to a wide variety of matching problems including function and parameterised matching, swap matching, swap-mismatch, k-difference, k-difference with transpositions, overlap matching, edit distance/LCS and L"1 and L"2 rearrangement distances. The resulting online algorithms bound the worst case running time per input character to within a log factor of their comparable offline counterpart