The WF runtime engine executes workflows by using runtime services. The runtime service model gives the host application the flexibility to provide various services to the WF runtime engine. This section describes the runtime services that are provided by WF and the out-of-box implementations of those services.
See the Windows Workflow Foundation Services and Developing Windows Workflow Foundation Services sections in the WF Programming Guide for more information about the runtime service implementations.
The WF runtime provides four services. These services have out-of-box implementations, or, host applications can implement their own services and provide them to the workflow runtime.