His description of the different frp approaches starts at section 2.1 of the thesis. http://www.testblogpleaseignore.com/wp-content/uploads/2012/04/thesis.pdf Then in 3.1 describes implementation of discrete signals. I don't think he gives a denotational semantics.
I was thinking, the event, is the derivative of the specific continuous signal it corresponds to, all other continuous signals of the system held equal.  Applying the partial derivative, is like sampling, or discrete time stepping.  But it is samplying the entire state, or multivariate structure not just the specific symbol. This made more sense unarticulated.  I'll need to think a bit.