Validates the user input.
Parameters: transientVars - Variables that will not be persisted. These include inputsgiven in the Workflow.initialize and Workflow.doAction method calls.There are two special variable names: entry (object type:com.opensymphony.workflow.spi.WorkflowEntry) and context(object type: com.opensymphony.workflow.WorkflowContext).Also, any variable set as a com.opensymphony.workflow.Register), will also beavailable in the transient map, no matter what. These transient variables only last throughthe method call that they were invoked in, such as Workflow.initializeand Workflow.doAction. Parameters: args - The properties for this function invocation. Properties are createdfrom arg nested elements within the xml, an arg element takes in a name attributewhich is the properties key, and the CDATA text contents of the element map tothe property value. Parameters: ps - The persistent variables that are associated with the currentinstance of the workflow. Any change made to the propertyset are persisted tothe propertyset implementation's persistent store. throws: InvalidInputException - if the input is deemed to be invalid