Syntactic Graphs: A Representation for the Union of All Ambiguous Parse Trees

In this paper, we present a new method of representing the Surface syntactic structure of a sentence. Trees have usually been used in linguistics and natural language processing to represent syntactic structures of a sentence. A tree structure shows only one possible syntactic parse of a sentence, but in order to choose a correct parse, we need to examine all possible tree structures one by one. Syntactic graph representation makes it possible to represent all possible surface syntactic relations in one directed graph (DG). Since a syntactic graph is expressed in terms of a set of triples, higher level semantic processes can access any part of the graph directly without navigating the whole structure. Furthermore, since a syntactic graph represents the union of all possible syntactic readings of a sentence, it is fairly easy to focus on the syntactically ambiguous points. In this paper, we introduce the basic idea of syntactic graph representation and discuss its various properties. We claim that a syntactic graph carries complete syntactic information provided by a parse forestmthe set of all possible parse trees.