11. A non-transitory computer-accessible memory medium comprising program instructions for runtime execution of one or more tasks defined in a workflow process language, wherein the program instructions are executable by a processor to: at runtime: obtain a description of the one or more tasks from a process ontology (PO), the process ontology (PO) defining a hierarchical taxonomy of executable tasks, each task referring to at least one frame of a hierarchical frame taxonomy of the process ontology (PO); identify at least one task parameter as described in the frame description to which the task refers; resolve the value of the at least one task parameter, comprising determining the value of the at least one task parameter; select a most specific applicable version of the task from a plurality of versions of the task contained in the task taxonomy of the process ontology (PO) based on the resolved value of the at least one task parameter; execute the most specific applicable version of the task.
11. A non-transitory computer-accessible memory medium comprising program instructions for runtime execution of one or more tasks defined in a workflow process language, wherein the program instructions are executable by a processor to: at runtime: obtain a description of the one or more tasks from a process ontology (PO), the process ontology (PO) defining a hierarchical taxonomy of executable tasks, each task referring to at least one frame of a hierarchical frame taxonomy of the process ontology (PO); identify at least one task parameter as described in the frame description to which the task refers; resolve the value of the at least one task parameter, comprising determining the value of the at least one task parameter; select a most specific applicable version of the task from a plurality of versions of the task contained in the task taxonomy of the process ontology (PO) based on the resolved value of the at least one task parameter; execute the most specific applicable version of the task. 12. The non-transitory computer-accessible memory medium of claim 11 , wherein said resolving comprises sending a message to a source indicated in the frame description, if the parameter value is not defined in a current process environment.