As described in How rules define scenario behavior, there is a rich syntax available for defining conditions. Traditionally, you would expect to have to learn the language for defining conditions, specify a condition in a rule, and then have some facility that will check your input and inform you whether or not it is valid.

Event Modeler takes a different approach, in that it provides for graphical programming. With graphical programming, you assemble the condition by selecting from a number of options, gradually piecing it together. The advantage of this approach is that you do not necessarily need to know the intricacies of the language in any great detail and will be unable to make syntactic mistakes. With a little practice you can rapidly become as fast as someone who is typing in the condition.