DCharts have their roots in David Harel's statecharts, which have been a part of UML now (with some modification). There are a number of variants of statecharts, mostly because the semantics of statecharts is not rigorously defined. This situation limits the reusability of statecharts models.
DCharts reuse all the concepts presented in statecharts. Extensions are added so that DCharts models are able to express models of all the statecharts variants. They can even be used to model the DCharts formalism itself. (This capability of meta-modeling is extremely interesting and cool!)
Some of the important extensions to original statecharts are summarized below. A complete description can be found in my master's thesis.