Using metadata to query passive data sources

In the not too distant past, the amount of online data available to general users was relatively small. Most of the online data was maintained in organizations' database management systems and accessible only through the interfaces provided by those systems. The popularity of the Internet, in particular, has meant that there is now an abundance of online data available to users in the form of Web pages and files. This data, however, is maintained in passive data sources, that is sources which do not provide facilities to search or query their data. The data must be queried and examined using applications such as browsers and search engines. We explore an approach to querying passive data sources based on the extraction, and subsequent exploitation, of metadata from the data sources. We describe two situations in which this approach has been used, evaluate the approach and draw some general conclusions.