This paper describes concepts and features of a Web-based system called XRL/flower for carrying out Petri-net based workflows described with XRL (eXchangeable Routing Language). XRL/flower uses XML technology and is implemented in Java on top of the Petri-net Kernel PNK. Standard XML tools can be deployed to parse, check, and handle XRL documents. The XRL enactment application is complemented with a Web server, allowing actors to interact with the system through the internet. A database allows the enactment engine and the Web server to exchange information with each other. Since XRL is instance based, a modelled workflow serves as a template that needs to be copied and may be possibly refined for enactment. For that purpose XRL constructs are automatically translated into Petri-net constructs. As a result, the system is easy to extend: For supporting a new control flow primitive, the engine itself does not need to change. Furthermore, the Petri net representation can be analyzed using state-of-the-art analysis techniques and tools.