Excerpt from the abstract of a research paper by Bastian Schäffer:
The OGC Web Geoprocessing Service specification provides a means to perform distributed web-based processing on geodata. However, the specification does not provide the ability to dynamically deploy and undeploy processes. This was the starting point for this paper to extend the specification with a generic means to deploy and undeploy processes at runtime, by adding two new operations to the WPS interface. Since the proposed approach allows any kind of processes to be deployed, specialized deployment profiles have to be offered.
Read the full paper:Schaeffer_-_Towards_a_Transactional_Web_Processing_Service.pdf
The code is part of the WPS trunk (and therefore binary releases).