Discovering non-trivial matching subsequences from two time series is very useful in synthesizing novel time series. This can be applied to applications such as motion synthesis where smooth and natural motion sequences are often required to be generated from existing motion sequences. We first address this problem by defining it as a problem of l--join over two time series. Given two time series, the goal of l--join is to find those non-trivial matching subsequences by detecting maximal l-connections from the -matching matrix of the two time series. Given a querying motion sequence, the l--join can be applied to retrieve all connectable motion sequences from a database of motion sequences. To support efficient l--join of time series, we propose a two-step filter-and-refine algorithm, called Warping Time Series Join (WTSJ) algorithm. The filtering step serves to prune those sparse regions of the -matching matrix where there are no maximal l-connections without incurring costly computat...