This technical report describes in detail the VSDG, the PDG (program dependence graph), and CFG (control-flow graph) program representations. It describes a way to generate a PDG from a VSDG, and a CFG from a PDG, resulting in a linear program from a VSDG.
The Value State Dependence Graph (VSDG) is a high-level intermediate representation for software procedures. It represents values as having an operation plus inputs plus a virtual "state" input used to ensure the ordering of side-effects is explicitly maintained. It makes many optimizations simple, but is very difficult to convert into linear code efficiently.