Standards for exchange of purchasing information, such as ANSI X-12 for EDI, have been used by large industries (e.g. retail and auto) for almost 30 years. Newer web-based tools and new standards hold the promise of reduced cost and wider applicability. For many small to medium sized enterprises, the cost and rigidity of existing tools out weight the prospective gains, which must be amortised over comparatively few transactions. In this paper, we describe the development of an N-tiered, object-oriented, architecture for interacting with suppliers based on emerging web tools. We explore the ways in which the project was required to adapt to existing purchasing systems and the ways that the project evolved during its development. We identify patterns in the inevitable evolution of requirements during the implementation, and we describe the ways that the architecture facilitated the satisfaction of these changing requirements. By analysing the major “transition points” during the development, we attempt to document the fundamental nature of evolving requirements and the need to explicitly reflect them in adaptable e-business architectures.