GPSG Parsing, Bidirectional Charts, and Connection Graphs

Ttfs paper describes a tractable method for parsing GPSG grmnmars without ,altering the modularity and expressiveness of this tbnnalism. The proposed method is based on a constraint propagation mech,'ufism which reduces the number of unnecessary structures built at parse thne through the early detection of inadmissible local trees. The propagation of constraints is rendered efficient by indexing constraints and categories in a connection graph m~d by using a bidirectional chat1 pm~er together with a botlore-up strategy centered around head constituents.