michigan informatics

How Search Engines Work: The Ranking Algorithm

How a search engine ranks the results of your search is possibly the most important component of a search engine. Most searches will retrieve thousands of results. Since you probably will only look through the first 1-2 pages of results, you need the most relevant results to appear first. Variable features which can affect your search results include:

• Location and Frequency
  All search engines look at the location and frequency of words in a page. If a term appears near the top of a web page, such as in the title or in the first few paragraphs of text, it is assumed that the page is more relevant than if the term is used at the bottom of the page. Pages where the words appear more frequently in relation to the other words on the page also qualifies the page as being more relevant than other web pages.
• Link Analysis
  This feature analyzes how web pages link to each other and then uses this information to determine the “importance” of each page. If a page is linked to from a large number of other pages, then it is ranked more highly.
• Clickthrough Measurement
  Some search engines also use clickthrough analysis. This means that a search engine might watch what results someone selects from a particular search, then eventually drop high-ranking pages that are not attracting clicks, while promoting lower-ranking pages that do pull in visitors.