Complexity of Dependencies at the Syntactic Level and at the Discourse Level

Aravind K. Joshi is, at present, the Henry Salvatori Professor of Computer and Cognitive Science at the University of Pennsylvania. He served as the Director of the Institute for Research in Cognitive Science (IRCS) at the University of Pennsylvania from 1990 to 2001. His honors include: Guggenheim Fellow, Fellow of IEEE, a Past President of ACL, Fellow of ACM and Founding Fellow of the AAAI. He was awarded the Research Excellence Award of the International Joint Conference on Artificial Intelligence, IJCAI (1997) and an Honorary Degree from the University of Paris in 2001. He is a member of the National Academy of Engineering. In 2002, he was awarded the Lifetime Achievement Award by ACL and in 2003, he won the David Rumelhart Award form the Cognitive Science Society. In 2005, he was awarded the Benjamin Franklin Medal for Cognitive Science by the Franklin Institute in Philadelphia. Professor Joshi works in the areas of computational linguistics, mathematical and processing models of language, artificial intelligence and cognitive science.
Abstract: We will first discuss some issues (which have been extensively investigated in recent years) concerning the complexity of dependencies at the syntactic level. We will then present some data about the types of dependencies that arise at the discourse level. This work is based on the Penn Discourse Treebank (PDTB) which consists of annotations of discourse connectives (explicit and implicit), their arguments, their attributions and senses. We will compare these dependencies to the ones we see at the syntactic level; raise some issues; propose some conjectures concerning the relative complexities at the syntactic and at the discourse level. This is joint work with Alan Lee, Rashmi Prasad, Nikhil Dinesh (all from UPenn) and Bonnie Webber (Edinburgh).