I am a Research Fellow in the Information Sciences and Technologies Laboratory at the Xerox Palo Alto Research Center, where I am manager of research in Natural Language Theory and Technology. I am also a Consulting Professor in the Linguistics Department at Stanford University and a Principal of Stanford's Center for the Study of Language and Information.

In more recent work, I have investigated mathematical extensions to linguistic formalisms that insightfully characterize various kinds of information propagation phenomena such as long-distance dependencies, coordination, and default feature assignments. With John Maxwell, I have explored computational mechanisms for solving disjunctive constraint systems and for propagating informational constraints across traditional linguistic module boundaries. I have also worked on data-oriented, probabilistic extensions to Lexical Functional Grammar (in collaboration with Rens Bod), problems of agreement involving indeterminate feature values (with Mary Dalrymple), and the formal properties of LFG generation (with Juergen Wedekind). My selective bibliography lists papers on these and other topics.

I am a past President of the Association for Computational Linguistics (1979), a co-recipient of the 1992 ACM Software System Award, and a Fellow of the ACM. During 1995-1996 I was a Fellow-in-Residence at the Netherlands Institute for Advanced Study in the Humanities and Social Sciences.