[Editors] MIT lecture search engine aids students

[Elizabeth Thomson]

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT lecture search engine aids students
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For Immediate Release
TUESDAY, NOV. 13, 2007
Contact: Elizabeth A. Thomson, MIT News Office -- Phone: 617-258-5402  
-- Email: thomson at mit.edu

PHOTO AVAILABLE


CAMBRIDGE, Mass.--Imagine you are taking an introductory biology  
course. You're studying for an exam and realize it would be helpful  
to revisit the professor's explanation of RNA interference.  
Fortunately for you, a digital recording of the lecture is online,  
but the 10-minute explanation you want is buried in a 90-minute  
lecture you don't have time to watch.

A new lecture search engine developed at MIT's Computer Science and  
Artificial Intelligence Laboratory (CSAIL) could help with this  
dilemma. Created by a team of researchers and students led by MIT  
associate professor Regina Barzilay and principal research scientist  
James Glass, the Web-based technology allows users to search hundreds  
of MIT lectures for key topics.

Although the prototype system focuses on MIT, the technology could  
eventually be applied to lectures from around the world.

“Our goal is to develop a speech and language technology that will  
help educators provide structure to these video recordings, so it's  
easier for students to access the material,” said Glass, who is head  
of CSAIL's Spoken Language Systems Group.

More than 200 MIT lectures are currently available on the site  
(web.sls.csail.mit.edu/lectures/). So far, most of the users are  
international students who access the lectures through MIT's  
OpenCourseWare (OCW) initiative, which makes curriculum materials for  
most MIT courses available to anyone with Internet access. Although  
the lecture-browsing system is still in the early development stages,  
a recent announcement in OCW's newsletter has drawn increased traffic  
to the site.

Barzilay and Glass expect the system will be most useful for OCW  
users and for MIT students who want to review lecture material. MIT  
World, a website that provides video of significant MIT events such  
as lectures by speakers from MIT and around the world, is also  
participating in the project.

Many MIT professors record their lectures and post them online, but  
it's difficult to search them for specific topics. Because there is  
no way to easily scan audio, as you can with printed text, “you end  
up watching the whole thing, and it's hard to keep focused,” said  
Barzilay, the Douglas T. Ross Career Development Associate Professor  
of Software Development in the Department of Electrical Engineering  
and Computer Science.

On the prototype web site, users can search lectures for any term  
they want, and then play the relevant sections.

The lecture transcripts are created by speech recognition software.  
One major challenge is that the lectures usually contain many  
technical terms that might not be in the computer program's  
vocabulary, so the researchers use textbooks, lecture notes and  
abstracts to identify key terms and feed them into the computer.

“These lectures can have a very specialized vocabulary,” said Glass.  
“For example, in an algebra class, the professor might talk about  
Eigenvalues.”

When properly adapted to a speaker and topic, the lecture-based  
speech recognizer gets about four out of five words correct, however  
most of the errors occur in words that are not critical to the  
lecture topic, i.e., not the key vocabulary terms that people would  
use to search.

Once the transcript is complete, a language processing program  
divides the text into sections by topic. Chunks of text, about 100  
words each, are compared with each other using a mathematical formula  
that calculates the number of overlapping words between the text  
blocks. Each word is weighted so that repetition of key terms has  
more weight than less important words, and chunks with the most  
similar words are grouped into sections.

In the future, Barzilay and Glass hope to add a lecture summarization  
feature to the language processing system. They also want to get  
users more involved in the project, by incorporating a Wikipedia-like  
function that would let users correct errors in lecture transcripts  
and allow them to add lecture notes.

The researchers presented their project at the Interspeech 2007  
conference in Antwerp, Belgium, in August. The project was originally  
funded by Microsoft through the iCampus program and is now funded by  
the National Science Foundation.

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Written by Anne Trafton, MIT News Office