Various technologies and techniques are disclosed for creating and executing extensible processes across multiple application components. A declarative feature is provided to allow partially ordered steps in an extensible process spanning multiple application components to be defined in a declarative format. A developer can define the minimum base steps in a first application component. Other application components can then provide additional partially ordered steps and/or actions to the extensible process. The declarative feature allows the partially ordered steps to have an associated step action. A sequencer is provided that assembles the partially ordered steps together from the multiple application components into a computational sequence having a total ordering. The sequencer executes the computational sequence in that total ordering upon receiving an execution request.