For details on modeling using EMRALD see the documentation - https://emraldapp.inl.gov/docs/

Emrald modeling example 1

Constructing an EMRALD model consists of building multiple state diagrams with pieces corresponding to aspects of traditional PRA modeling. This model is most effectively created through the web based GUI, although the GUI does export an XML file that could also be modified with an in-depth knowledge.  

At any given moment when running an EMRALD model, it is in a set of states. These states determine what the model is to do; what events to monitor for; and where to transition.