24 Oct 2013

Adam Lopez is visiting Natlang today, October 24th. He is giving a talk about Synchronous Formal Grammars and the details are below.

Location: TASC1 9204W

Date and Time : Oct 24, 2013. 11:30am to 12:30pm


Text rewriting applications like machine translation, summarization, and paraphrasing often model textual equivalence through syntactic transformations expressed in synchronous grammars. These include synchronous extensions to context-free, tree-adjoining, tree-substitution, and many other formalisms. Today, there is a renewed interest in modeling equivalence through compositional semantics. I will describe one possible approach to semantics-preserving text rewriting: a synchronous extension to combinatory categorial grammar (CCG), an elegant formalism with many attractive properties, including both a clean syntax-semantics interface and efficient algorithms. The new formalism generates pairs of strings with identical semantics, subject to isomorphism constraints imposed by the lexicon. However, recognition poses a problem: it turns out that obvious extensions of algorithms used for synchronous CFGs do not work. I will sketch a possible solution to this problem based on a view of parsing as language intersection. Although this work is formal, the talk will be informal: I will give some tutorial background on CCG and intersection constructions before presenting the new formalism.


Adam Lopez works on problems at the intersection of algorithms, machine learning, formal language theory, and computational linguistics with applications to problems in natural language processing, particularly machine translation. He is an assistant research professor at Johns Hopkins University. He has also been a visiting scientist at SDL Research, a research fellow at the University of Edinburgh, and a Ph.D. student at the University of Maryland.