With the current explosion of information on the World Wide Web (WWW) a wealth of information on many different subjects has become available on-line. Numerous sources contain information that can be classified as semistructured. At present, however, the only way to access the information is by browsing individual pages. We cannot query web documents in a database-like fashion based on their underlying structure. However, we can provide database-like querying for semi-structured WWW sources by

more »

... uilding wrappers around these sources. We present an approach for semi-automatically generating such wrappers. The key idea is to exploit the formatting information in pages from the source to hypothesize the underlying structure of a page. From this structure the system generates a wrapper that facilitates querying of a source and possibly integrating it with other sources. We demonstrate the ease with which we are able to build wrappers for a number of internet sources in different domains using our implemented wrapper generation toolkit. ful to have the capability of issuing queries to this source which would allow us to query the source based on the structure in the pages. For instance, for each individual page we would like to be able to ask queries about one or more sections in the page, e.g. ' 'Find the Land boundaries and Area of France" Or we could ask queries that span multiple pages (i.e., countries) such as ' 'Find the National Produc¢ and Defense Ezpenditures of all cotmtries in Europe. ' ' We provide such a querying capability by building wrappers around WWW sources. A wrapper for a web source accepts queries 2 about information in the page(s) of that source, fetches relevant pages from that source, extracts the requested information and returns the results. There are two primary advantages to building wrappers around WWW sources: