《SSD1 1.1课件》.ppt

* Questions about C/S Given the description of Web servers above, what limitations can you see with this C/S model? In the above model, can the client receive personalized information? In your own explorations of the World Wide Web, what behaviors have you seen that the model above does not account for? * Beyond the Basic Model Server executes auxiliary(辅助的) applications. * * iphone4s * Browsing vs.Searching Browsing-Unfocused random passing from link to link around the web Searching-Using a search engine（有哪些信誉好的足球投注网站引擎） to locate a resource on the web. Searching may eventually run into browsing. Search Engine-A program（程序） that implements different search mechanisms（机制）, like indexing （索引）sites and its pages. * Searching the Web Browsing and searching Search engine is a program that allows one to search for keywords in files at one or more Internet sites. Google: Baidu: Excite: Lycos: AltaVista: * Types of Search Sites Search Engine – Featured Sites that maintain indexes or databases （数据库）of of the addresses of virtually all of the pages and documents on the Web. These indexes or databases maintained regularly using “spiders” for addresses of new documents that become available on the internet. Eg: Google * Types of Search Sites Web Directory-Featured Information organized into categories(分类，目录) and subcategorie(子类，亚类), mostly based on human effort. Only a fraction of net in web directories, and owners of relevant Web sites responsible for inclusion of their sites. Eg: Yahoo! * How to search Use a search site Type keywords (关键字)of your search into the search engine Search…. Use the help information offered by each search engine. * A search sample results * Apple A search sample results * Apple + food Commerce(商业) on the web Internet Service Providers Sell access to the internet in terms of log on service, email service, web publishing Establishing and maintaining web presence done through ISPs can be expensive. Price based on number of hits that can be han