In complex and diversified application context

flexibility is one of the key issues of workflow technology. As an important approach to improve the flexibility of system

reflection is also available to Workflow Management System (WfMS).This paper reifies the workflow process and its management respectively from structural and behavioral aspects

and as a result

a reflective model of workflow is designed. A model of Meta-Ohject Protocol (MOP) is proposed to abstract and pmgram on meta-level

including protocol declaration

meta-object association

pmtocol selection and meta-object management.The typical instance evolution example shows that reflection is effective to impmve the flexibility and adaptability of WfMS. The implementation of reflection is presented in the paper.