Context-Free Grammar Rewriting and the Transfer of Packed Linguistic Representations

We propose an algorithm for the transfer of packed linguistic structures, that is, finite collections of labelled graphs which share certain subparts. A labelled graph is seen as a word over a vocabulary of description elements (nodes, arcs, labels), and a collection of graphs as a set of such words, that is, as a language over description elements. A packed representation for the collection of graphs is then viewed as a context-free grammar which generates such a language. We present an algorithm that uses a conventional set of transfer rules but is capable of rewriting the CFG representing the source packed structure into a CFG representing the target packed structure that preserves the compaction properties of the source CFG.