In this paper, we describe a novel approach to the problem of dynamic task allocation among groups of heterogeneous agents. Specifically, we advocate the use of publish/subscribe messaging, a well-researched and commercially proven message brokering paradigm that is readily applicable to distributed control. We present Murdoch, an implemented publish-subscribe system, and explain how it can facilitate multi-robot coordination. The system allows the user a high-level interface for posing tasks to a group of autonomous homogeneous or heterogenous robots. Rather than assigning a task to an individual or a group, the user simply poses the task to the system as a whole (with no knowledge of individual agents).