anchor.diff:  /// </returns>
   let axiomatise
     (model : Model<Graph, _>)
  -  : Model<Axiom<SVGView, Command>, _> =
  +  : Model<Axiom<GView<Sym<Var>>, Command>, _> =
       withAxioms (axiomatiseGraphs model.Axioms) model
   
   
  
positive.code:           /// <summary>
            ///     The view of the source node.
            /// </summary>
            SrcView : ViewExpr<SVGView>
            /// <summary>
            ///     The name of the destination node.
            /// </summary>
  
negative.code:         /// </summary>
          Contents : Map<
              NodeID,
              (ViewExpr<GView<Sym<Var>>>
               * Set<OutEdge>
               * Set<InEdge>
               * NodeKind)> }
  