Rahul, the latest SCXML WD [1] describes a set of system variables which are read-only for the application. See section 5.5 [2]: "The Data Module maintains a protected portion of the data model containing information that may be useful to applications...."
This could be implemented in commons-scxml using an additional context and set it as the parent of the current root context. Some expression languages (such as ECMAScript) support scope chains and allow to attach scopes read only. Other expression languages may require a special treatment of this "system variable context". In this case it could be necessary to implement a special context which handles the read-only behavior. At the same time we could change the "eventname" and "eventvalue" variables to "_event.name" and "_event.value". What do you think? - Ingmar. [1] http://www.w3.org/TR/2008/WD-scxml-20080516/ [2] http://www.w3.org/TR/2008/WD-scxml-20080516/#SystemVariables
