Abstract: A thorough understanding of the way in which a workflow process is executing is essential to workflow rnanagement.By extracting information from workflow traces, such as system log data, workflow mining aims to discover the actual behavior of a workflow process. One of the challenging problems in workflow mining is to mine hidden tasks.Based on the traditional a-algorithm, an extended one which is called aH-algorithm to mine hidden tasks was proposed.After studying the situations where a hidden task may appear,the aH-algorithm inserts hidden tasks by judging the presences of parallel tasks.The mined workflow model was refined by fusing the same hidden tasks and removing the redundant ones.A prototype based on aH-algorithm was implemented.Experiments in the end show the fasibility and validity of the proposed algorithm.Furthermore,the restriction of the algorithm and related future work were also discussed and pointed out.

Key words: Workflow model, Workflow mining, Hidden tasks, Workflow net, Petri net