anchor.diff:  
   %% TODO: Single projection only!
   materialize({select, Projections},
  -            #state{predicate_output_id=PredicateOutputId}=State) ->
  -    %% Create a node for the result of the predicate.
  -    {ok, {OutputId, _, _, _}} = lasp:declare(?SET),
  +            #state{output_id=OutputId, predicate_output_id=PredicateOutputId}=State) ->
   
       %% Apply the projection.
       lasp:map(PredicateOutputId,
  
positive.code: 
  -include("lasp.hrl").
  
  -export([create/1]).
  
  -record(state, {set_id, projection_output_id, predicate_output_id}).
  
  -define(DEFAULT, <<"hi">>).
  
  %% @doc Create a SQL view from a textual specification.
  create(Specification) when is_list(Specification) ->
      %% Tokenize the string.
      {ok, Tokens, _EndLine} = ?SQL_LEXER:string(Specification),
  
  
negative.code:     ct:pal("Parse Tree: ~p", [ParseTree]),
  
      %% Create and return identifier.
      OutputId = materialize(ParseTree, #state{output_id=OutputId}),
  
      %% Return output identifier.
      {ok, OutputId}.
  