Scientific workflows (SWF) are traditionally coordinated and executed in a centralized fashion. This creates a single point of failure, forms a scalability bottleneck, and often leads to too much message traffic routed back to the coordinator. We have developed PADRES, a content-based publish/subscribe platform that serves as a runtime environment for the decentralized execution, control, and monitoring of SWF. Publish/subscribe is a natural paradigm for event-driven applications such as SWF management, as the loosely-coupled nature of publishers and subscribers relieves the coordinator from maintaining client connection and capability information. PADRES has been developed with features inspired by the requirements of SWF management. Its unique features include an expressive subscription language, composite subscription processing support, a rule-based matching and routing mechanism, a querybased historic data access mechanism, and support for the decentralized execution of SWFs specified in XML.