anchor.diff:  module xsd =
     open VDS.RDF
   
  -  let mapL f n =
  -    match n with
  -    | Node.Literal l -> (f l)
  -    | _ -> failwith (sprintf "%A is not a literal node" n)
  -
     let string =
       function
       | Node.Literal(Literal.String s) -> s
  
positive.code:     g.GetTriplesWithSubjectObject(uriNode p (Graph g), uriNode o (Graph g))
    let bySubjectPredicate p o (Graph g) =
      g.GetTriplesWithSubjectPredicate(uriNode p (Graph g), uriNode o (Graph g))
    let fromSingle f x g = f x g |> Resource.from
    let fromDouble f x y g = f x y g |> Resource.from
  
  
negative.code: 
  
  module triple =
    let uriNode (Sys u) (Graph g) = g.CreateUriNode(u)
    let bySubject u (Graph g) = g.GetTriplesWithSubject(uriNode u (Graph g))
    let byObject u (Graph g) = g.GetTriplesWithObject(uriNode u (Graph g))
    let byPredicate u (Graph g) = g.GetTriplesWithPredicate(uriNode u (Graph g))
  