Recent database research has given much attention to the specification of "flexible" transactions that can be used in interoperable systems. Starting from a quite different angle, Business Process Modelling has approached the area of communication modelling as well. The Language/Action perspective describes business processes by means of speech acts and commitments. These can be formalized by means of extended deontic logic. We argue that this logic provides the right concepts for specifying flexible transactions. To impose a modular structure on the specification, we make a distinction between the transaction level, the task level, and the contract. Extended deontic logic also offers the operators (communicative actions) by means of which one business process can be transformed into another. When these operators are provided to the subjects, business processes need no longer be seen as fixed once, but can become the subject of continuous negotiation and adaptation.