Presentation on theme: "CE80N Introduction to Networks & The Internet Dr. Chane L. Fullmer UCSC Winter 2002."— Presentation transcript:
CE80N Introduction to Networks & The Internet Dr. Chane L. Fullmer UCSC Winter 2002
February 26, 2002CE80N -- Lecture #152 General Information TA Office… –Trailer #15 is no more –TA offices moved to the ISB Contact TA for current info…
February 26, 2002CE80N -- Lecture #153 Web Search based Essay Essay based on Web search results –1-2 pages on any topic of interest –Must include results from at least four Web page references –References must be listed in a bibliography Due Today, February 26, 2002
February 26, 2002CE80N -- Lecture #154 Class Information Web page tutorial available on-line Web page submission: – to Subject: cmpe080n-assgn4 Final Exam –Last class session March 14, 2002
February 26, 2002CE80N -- Lecture #155 Personal Web Page of the Day A few brave souls…. So, here’s: –Robbie StockmanRobbie Stockman –Ryan RodriguezRyan Rodriguez
February 26, 2002CE80N -- Lecture #157 Description Of Functionality An automated search service allows one to find information that resides on remote computers.
February 26, 2002CE80N -- Lecture #158 Browsing Vs. Automated Searching The size of the Internet makes it impossible to find specific information by searching one computer at a time. –Called Browsing, like window shopping at the mall The solution is to use an automated search engine. –Like using the yellow pages and calling from home.
February 26, 2002CE80N -- Lecture #159 A Search Engine Helps Users Get Started Automated searching is especially helpful when a user first begins to explore a topic.
February 26, 2002CE80N -- Lecture #1510 A Search Tool Can Help Recover From Loss Automated search tools help users recover quickly when the location of information is lost.
February 26, 2002CE80N -- Lecture #1511 Automated Searching By Name One can search by specific name or content. NetScape -- search site Overture (formerly Goto.com)
February 26, 2002CE80N -- Lecture #1512 Search engines: –gather information globally –store it locally Servers do not have to search the entire Internet when responding to a user’s request. Caveat – Information can get stale… How An Automated Search Service Operates
Figure 25.1 Figure 25.1 An illustration of the two-step process an automated search service uses. (a) A spider program automatically contacts web sites and obtains a list of available items. (b) When someone uses a browser to contact the search engine, the server consults the database on its local disk.
February 26, 2002CE80N -- Lecture #1514 Modern Systems Search Web Page Contents Users can assume the search will look for Web pages matching the topic specified.
February 26, 2002CE80N -- Lecture #1515 How A Web Search Appears To A User Search services are: –Accessed through a Web site Search services: –Require user interaction –Use forms technology NetScape Search Site
February 26, 2002CE80N -- Lecture #1516 How A Search Engine Returns Results The search engine creates a Web page that has a link to each found topic. –Uses cgi technology to create pages dynamically
February 26, 2002CE80N -- Lecture #1517 Automated Search Services Use String Matching The simplest automated search mechanism is string matching. The user enters a topic, the search engine finds Web pages that contain that topic string. Google.comGoogle.com
February 26, 2002CE80N -- Lecture #1518 String Matching Advantages of string matching –Simplicity Disadvantage of string matching –Lack of semantics –Inability to tell the meaning of words “This sentence is NOT about trains, planes and automobiles”
February 26, 2002CE80N -- Lecture #1519 Advanced Search Programs Some search engines offer multi-key search service. –Group synonyms with a common theme together ie, hospital doctor nurse health
February 26, 2002CE80N -- Lecture #1520 Advanced Services- More Sophisticated Matching Some services offer the opportunity to give more detailed specifications. Use plus sign to denote a required term –LycosLycos
February 26, 2002CE80N -- Lecture #1521 Personalized Search Results Search engines keep information about users and use the information to select and order search results. –Results in different users getting different search results on same keys
February 26, 2002CE80N -- Lecture #1522 How An Automated Content Search Works The search service runs a program called a spider. –Explores Web –Compiles a list of topics –Stores list on server disk –Filters out articles, prepositions from text as one way to avoid storing useless information.
February 26, 2002CE80N -- Lecture #1523 Searches Are Restricted Automated search services search only the beginning of each page. –Use the special HTML tag: Allows specific keywords that do not appear in the browser –Gives the site better coverage from search engines
February 26, 2002CE80N -- Lecture #1524 Advertising Pays For Searching Web searching appears to be free. –Uses advertising to generate revenue
Example of Automated Search Services Figure 25.4 Examples of automated search services available on the World Wide Web. Although most services provide a general index to Web pages, a few are restricted to specific types of information. Infoseek Site Dogpile WebCrawler
February 26, 2002CE80N -- Lecture #1526 Significance Of Automated Web Search Automated search engines have become an essential part of finding information. –Growing rapidly on the Internet –A gigantic, freely accessible, global database at your disposal, 24/7…..
February 26, 2002CE80N -- Lecture #1527 Glossary Personalized Search Results – Results from a search engine that are personalized to the user who makes the request. Personalization depends on a history of searches and web accesses.
February 26, 2002CE80N -- Lecture #1528 Glossary Wide Area Information Server –(WAIS) An early automated search service that permitted one to locate documents that contain key words or phrases.