Using the Earley Algorithm we can use the Leo enhancement to create cached items for recognition. http://www.sciencedirect.com/science/article/pii/030439759190180AScott's algorithm on building parse trees doesn't take into account this enhancement. http://www.sciencedirect.com/science/article/pii/S1571066108001497Leo notes in his paper his algorithm builds an effective recognizer, but ultimately leaves out information that would be needed to construct the parse forest. Building the parse forest would require the transition items omitted by the enhancement and therefore undo the complexity gains. So I would like to know if there is research or findings on creating a parse forest that retains the complexity gains from the Leo enhancement without pushing the complexity from the recognizer to the parse forest generation. Basically, is there a linear time algorithm on LR(k) grammars for building sparsely packed parse forests? 
Is there any research or findings on creating parse forests on Earley parsers with Leo Joop Enhancements?
fl.formal languages;parsing