The derivation of business process execution language (BPEL) for web services from graph-oriented process models has attained wide focus in the literature. It is a challenging work owing to the fundamental differences between graph-oriented models and BPEL. In this paper, a transformation of activity diagrams (AD) into BPEL is presented, which concentrates on a specific kind of structure in graph-oriented process models called overlapped patterns (OPs). The structures of AD models containing OP are analysed, and an important subclass of OP, first-order OP, is defined. Then in the context of first-order OP, the applicable ranges of two existing transformation strategies of OP are discussed, and a new method is proposed for the cases that neither of them can handle.