Search Engines AGCM 4143 Electronic Communications in Agriculture

Searching As a Web user, you need to be familiar with at least one or two search engines As a Web designer, you must be aware of many types of search engines. Knowing how search engines work allows you to make your site easily available to their databases (This is one important step in promoting Web sites)

How Search Engines Work When you use a search engine, you are searching its database(s); you are not searching the entire Web Two basic types of search engines –Crawler-based or Spider-based –Human-powered directories

Web Crawlers or Spiders Crawler-based or Spider-based (Google is a good example.) –Robots owned by the search engine companies continually search the Web for new sites to add to their database of Web pages –These “crawlers” or “spiders” continually add new sites and re-catalog old ones based on updates that are made to the sites

Web Crawlers or Spiders –Spiders use various methods to catalog URLs Information in the section near the top of the HTML document –Page title (indicated by the tag) –Meta tags, including descriptions and keywords (e.g., the description is indicated by the tag ) –Body text content –ALT text associated with graphics (indicated by the tag

Web Crawlers or Spiders –The database-query software of each search engine is tuned to rank sites based on customized criteria (called an algorithm) –So, the results of a Yahoo search are different than the results of Google search –The main ranking criteria are... Frequency of occurrences of the search term Location of the search term in the page –If the term occurs in the title or near the top of the body, the site receives a higher ranking

Human-Powered Directories Human-Powered Directories (Looksmart.com is an example) –These search engine companies gather data manually –Webmasters request that their sites be added to the database and provide a description of their site provides this service with hundreds of search engines for $79/yearwww.submit-it.com –Also, search engine employees independently review sites to be added to the database

Human-Powered Directories Many online service providers (OSPs) use both methods by paying two or more search engine companies to “power” their site (e.g., MSN) Also, OSPs (and most search engine companies) maintain a clickable directory of popular subjects in their search engine database

Searching Search engines (most have clickable directories, too) –Yahoo –AltaVista –Lycos –WebCrawler –Go (formerly Infoseek) –Excite –Google –Dogpile –Ask Jeeves

Search Strings Algorithms are simple rules the search engine follows for choosing how to respond to a query Search strings help users narrow searches while playing by the database’s algorithm rules –A Google search for “Cowboys” returns every Google database entry with a reference to cowboys (~1,510,000 hits)

Search Strings –A Google search for “Dallas” +”Cowboys” returns every URL referring to Dallas and Cowboys, regardless of whether the words appear together or not (~402,000 hits) –A Google search for “Dallas Cowboys” returns only the pages where the words occur together (~262,000 hits) –A Google search for “Cowboys” -”Dallas” returns only the pages that contain the word cowboys without the word Dallas (~741,000)

Search Exercise Use three different search engines of your choice to find information on the Web about Arkansas soybeans. Use these three search strings with each of the three search engines –“Arkansas” +”Soybeans” –“Arkansas Soybeans” –“Arkansas Soybeans” -”extension” Write (type) up your results, and include them in a short narrative comparing the features, effectiveness, and usability of the three search engines. Attach your Word document to an e- mail addressed to