iTaSC DSL is a Domain Specific Language for constraint-based programming, more specifically iTaSC.
For more explanation and examples, please read D. Vanthienen, M. Klotzbuecher, T. De Laet, J. De Schutter, and H. Bruyninckx, Rapid application development of constrained-based task modelling and execution using domain specific languages, in Proc. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Tokyo, Japan, 2013, pp. 1860–1866.
It is recommended to use the devel branch for the DSL as well as the iTaSC stacks.
For the Orocos reference implementation (in a ROS environment): One way is to send events in the Orocos task browser through the event_firer component that is automatically started when parsing and deploying an application.
Another, more user-friendly way, is to send events on the /itasc/ ros_common_events_in ROS topic (see README of the itasc_dsl repository).
A GUI to send events can be found on: https://bitbucket.org/apertuscus/python_gui
Look for an example at the itasc_erf2012_demo, that contains a run_eventgui.sh, launching this GUI with events for the iTaSC ERF2012 tutorial.