Service workflow management which consolidates multiple services to achieve business goals has become a critical issue in service-oriented computing. Due to the unique feature of service workflows such as full distribution and high dynamicity, the contemporary workflow technology has exhibited inefficiency, vulnerability, inflexibility and lack of adaptability. Based upon the authors' previous work on peer-to-peer based workflow management and seamless integration of agents and Web services, this paper innovatively presents SwinDeW-A which is a decentralised service workflow management framework based on peer-to-peer and agent technologies. Based on this framework, this paper also discusses how autonomous service level agreement negotiation, decentralised process enactment, and autonomous process adaptation can be achieved. The proposed approach takes advantages of the peer-to-peer computing technology and the agent technology to provide more efficient, reliable, flexible and adaptive service workflow management.