The Filtering Approaches for the Improved Boyer-Moore Approximate String Matching

The Boyer-Moore algorithm is to solve exact string matching. Here, the Bad Character Rule of the Boyer-Moore algorithm is extended to solve approximate string matching. Although Tarhio and Ukkonen introduce a basic algorithm, it is similar to the Horsool algorithm. We utilize the concept of their algorithm to implement the Bad Character Rule, and we will obtain a new shift length. When the window needs to be shifted in filtering stage, there is a chance to shift larger. This paper also explains two simple filtering approaches, and we easily combine any one of the filtering method to our algorithm. These filtering rules are easy to understand. One of them comes from the obvious concept of the definition of edit distance. Another uses a special relationship between edit distance and Hamming distance.