The foundation of Workflow is an executable workflow. The framework includes an engine that performs the workflow.
It allows you to write pieces of workflow logic in code.
I suggest reading this developer introduction on MSDN.
UML does nothing - you cannot use code as part of your UML or execute your UML workflows.
UML is intended as a tool for documentation and communication.
Workflow Foundation is a software tool that is used to model and execute workflows.
Domain modeling suitability update.
Since the core of the Workflow Foundation is workflow modeling, you must use it for this. If the primary domain is not a workflow, you should model it in a more traditional way. You can use the Workflow Foundation to model the workflows of your model.
Odded source share