What Science Underlies Natural Language Engineering?

One of the most thought-provoking proposals I have heard recently came from Lori Levin during the discussion that concluded the EACL 2009 Workshop on the Interaction between Linguistics and Computational Linguistics. Lori proposed that we should form an ACL Special Interest Group on Linguistics. At first blush, I found the idea weird: Isn’t it a little like the American Academy of Pediatrics forming a SIG on Medicine (or on Children)? Second thoughts, however, revealed the appropriateness of the idea: In essence, linguistics is altogether missing in contemporary natural language engineering research. In the following pages I want to call for the return of linguistics to computational linguistics. The last two decades were marked by a complete paradigm shift in computational linguistics. Frustrated by the inability of applications based on explicit linguistic knowledge to scale up to real-world needs, and, perhaps more deeply, frustrated with the dominating theories in formal linguistics, we looked instead to corpora that reflect language use as our sources of (implicit) knowledge. With the shift in methodology came a subtle change in the goals of our entire enterprise. Two decades ago, a computational linguist could be interested in developing NLP applications; or in formalizing (and reasoning about) linguistic processes. These days, it is the former only. A superficial look at the papers presented in our main conferences reveals that the vast majority of them are engineering papers, discussing engineering solutions to practical problems. Virtually none addresses fundamental issues in linguistics. There’s nothing wrong with engineering work, of course. Every school of technology has departments of engineering in areas as diverse as Chemical Engineering, Mechanical Engineering, Aeronautical Engineering, or Biomedical Engineering; there’s no reason why there shouldn’t also be a discipline of Natural Language Engineering. But in the more established disciplines, engineering departments conduct research that is informed by some well-defined branch of science. Chemical engineers study chemistry; electrical engineers study physics; aeronautical engineers study dynamics; and biomedical engineers study biology, physiology, medical sciences, and so on. The success of engineering is also in part due to the choice of the “right” mathematics. The theoretical development of several scientific areas, notably physics, went alongside mathematical developments. Physics could not have accounted for natural phenomena without such mathematical infrastructure. For example, the development of (partial) differential equations went hand in hand with some of the greatest achievement in physics, and this branch of mathematics later turned out to be applicable also to chemistry, electrical engineering, and economics, among many other scientific fields.