The invention provides improved methods and apparatus for workflow editing. Such methods and apparatus permit, for example, user-defined and/or other tasks to be combined in any combination or combinations to specify a workflow. The tasks can be linked for direct, serial processing and/or for conditional processing that includes branching and/or looping. The invention also improved methods and apparatus of workflow definition and processing with extensible actions. The invention provides, further, improved methods and apparatus for workflow definition and processing which utilize workflow variables for communication of data and control information among tasks within a workflow. The invention provides, still further, improved methods and apparatus of workflow definition and processing with enhanced messaging. The invention provides, still yet further, improved methods and apparatus for workflow definition and processing which permit definition of hierarchically enumerated data types and for for definition of "plans" to collect, e.g., for storage, data such as the aforementioned hierarchical data types.