While the specification languages of workflow management systems focus on process execution semantics, the successful development of workflows relies on a fuller conceptualisation of business processing, including process semantics. For this, a wellspring of modelling techniques, paradigms and informal-formal method extensions which address the analysis of organisational processing structures (enterprise modelling) and communication (based on speech-act theory), is available. However, the characterisations indeed the cognition of workflows still appears coarse. In this paper, we provide the complementary, empirical insight of a real-scale business transaction workflow. The development of the workflow model follows a set of principles which we believe address workflow modelling suitability. Through the principles, advanced considerations including asynchronous as well as synchronous messaging, temporal constraints and a service-oriented perspective are motivated. By illustrating the suitability principles and with it the inherent complexity of business transaction domains, we offer timely insights into workflow specification extension, and workflow reuse and deployment.