[Haskell-cafe] graphical editor links ?

I am designing some graphical editor ( visio - dia like) and would be interested to hear any pointer to help me think on the architecture of this, in term of data structure/ EDSL/ persistence/ paradigm (FP/ FRP/...) for the different "layers of abstraction " I may see , like rendering libraries ( gtk/wx..)<-> model of the diagram<-> semantics ( this is a state diag/ archimate / mind mapping , i.e. what the glyph and lines means ) <-> persistence Any help & pointers welcomed ! ( and which place is best to discuss this ?) Luc