// class dictionary
Cd_graph = < first > Adj < rest > Adj_list .
Adj = < vertex > Vertex < ns > Neighbors "." .
Neighbors : Construct | Alternat .
Construct = "=" < c_ns > Any_vertex_list .
Alternat = ":" < first > Vertex "|" < second > Vertex .
Any_vertex : Labeled_vertex | Syntax_vertex .
Syntax_vertex = < string > DemString .
Labeled_vertex = "<" < label_name > DemIdent ">" 
                     < class_name > Vertex .
Adj_list : Empty_cd_graph | Cd_graph .
Any_vertex_list : Empty | Nany_vertex_list .
Nany_vertex_list = 
  < first > Any_vertex < rest > Any_vertex_list .
Empty = .
Empty_cd_graph = .
Vertex = < name > DemIdent .