Formal Languages and Algorithms for Similarity based Retrieval from   Sequence Databases
  The paper considers various formalisms based on Automata, Temporal Logic and Regular Expressions for specifying queries over sequences. Unlike traditional binary semantics, the paper presents a similarity based semantics for thse formalisms. More specifically, a distance measure in the range [0,1] is associated with a sequence, query pair denoting how closely the sequence satisfies the query. These measures are defined using a spectrum of normed vector distance measures. Various distance measures based on the syntax and the traditional semantics of the query are presented. Efficient algorithms for computing these distance measure are presented. These algorithms can be employed for retrieval of sequence from a database that closely satisfy a given. 
A. Prasad Sistla