IB ITGS

nternet search engine. But the front pages of such sites as Google, Yahoo and Altavista are hiding hugely complex and refined systems for cataloguing and analysing millions of web pages

cheat the engines to come top of the search rankings.

find out how they were invented, how they work, and what the future holds for the programs that effectively control our access to the web.

The system has several underlying database tables, including zip codes, cities and station data. The zip code and city tables, in addition to containing information about the locations, also include the latitude and longitude for the centroid each location.

At the core, the system works based on latitudes and longitudes.

Once we have the latitude and longitude, we perform a series of calculations based on the Great Circle Calcuation (GCC), which helps us to determine distances on a curved surface (ie. the Earth - and we are assuming that it is not flat). Using the GCC, we look for stations near the latitude and longitude, based on a 100 mile radius from that point. From that list of stations, which is too inclusive, we start our process of narrowing down the results to the actual stations that can be heard.

Most people using a search engine expect to find what they are looking for on the first page of results,

good results should have "good pages, text rich content, and good links pointing to you".

The block was an "overreaction," says Michael Klag, the dean of Johns Hopkins School of Public Health, which maintains the POPLINE database.

An inquiry into why the world's largest database on reproductive health blocked searches using the term "abortion" has found the restriction was put in place because of articles from an abortion advocacy magazine available on the site.