An exciting trend in enterprise computing lies in the integration of applications across an organisation and even between organisations. This allows the provision of services by automated business processes that coordinate activity among several collaborating companies. The best successes in this type of distributed system come through use of Web Services technologies, which allow interoperation between applications and workflows, through open standards based on XML and SOAP. In this talk we discuss some unresolved issues which confront a designer who wants to ensure the consistency of data across several collaborating workflows or applications.