plaintiffs offered, and the Court qualified, Nunberg as an expert witness on automated

classification systems.

7

When compiling and categorizing URLs for their category lists, filtering software

companies go through two distinct phases.  First, they must collect or  harvest  the

relevant URLs from the vast number of sites that exist on the Web.  Second, they must

sort through the URLs they have collected to determine under which of the company's

self defined categories (if any), they should be classified.  These tasks necessarily result

in a tradeoff between overblocking (i.e., the blocking of content that does not meet the

category definitions established by CIPA or by the filtering software companies), and

underblocking (i.e., leaving off of a control list a URL that contains content that would

meet the category definitions defined by CIPA or the filtering software companies).  

a.  The  Harvesting  Phase

Filtering software companies, given their limited resources, do not attempt to

index or classify all of the billions of pages that exist on the Web.  Instead, the set of

pages that they attempt to examine and classify is restricted to a small portion of the Web. 

The companies use a variety of automated and manual methods to identify a universe of

7

  Geoffrey Nunberg (Ph.D., Linguistics, C.U.N.Y. 1977) is a researcher at the Center

for the Study of Language and Information at Stanford University and a Consulting Full

Professor of Linguistics at Stanford University.  Until 2001, he was also a principal

scientist at the Xerox Palo Alto Research Center.  His research centers on automated

classification systems, with a focus on classifying documents on the Web with respect to

their linguistic properties.  He has published his research in numerous professional

journals, including peer reviewed journals.

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