You can create new versions of your human task, so that multiple versions of those same tasks can co-exist in a runtime environment.
To create a version of a human task, it is important that you plan ahead. Specifically, you will need to consider how the client interacts with the task, and how the task itself is set up. To allow for seamless introduction of new versions, it is a good idea to anticipate the need ahead of time, and set things up in the manner described in the associated topics.
In addition, it is important to note that interface specifications of different versions need to remain the same.
Of critical importance, the two versions must have the same name and namespace, but have different valid-from dates. In addition, where applicable, they must also have the same interface. In other words, it is with different valid-from dates that multiple versions of the same task are distinguished. In practice, the runtime engine could use a new version of a task that is set to become valid today, even if an older version of that task was still being used.
When a client invokes a task, that client can be configured either to choose a specific version each time, or to pick up the currently valid version of the task. This is the basic concept behind early binding and late binding.
With early binding, a client is hard-wired to a task in such a way as to force a continued relationship between the two of them, even if another version of the task becomes available. In contrast, with late-binding the relationship between the client and the task is dynamic in that it is resolved in the runtime environment.
In other words, if the caller instantiates a task using early binding, a specific version of the task is used to create that instance, and if they use late binding, the currently valid version of the human task is used.
See the whitepaper on developerWorks called Versioning and dynamicity with WebSphere Process Server and the podcast called WebSphere Technical Podcast series: SOA programming model, Part 5: Managing change in Web services components and applications