CE80NCE80NIntroduction to NetworksIntroduction to Networks

&&The InternetThe Internet

Dr. Chane L. Fullmer

UCSC

Winter 2002

February 26, 2002 CE80N -- Lecture #15 2

General InformationGeneral Information

TA Office…– Trailer #15 is no more– TA offices moved to the ISB

• Contact TA for current info…

February 26, 2002 CE80N -- Lecture #15 3

Web Search based EssayWeb 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, 2002 CE80N -- Lecture #15 4

Class InformationClass InformationWeb page tutorial available on-lineWeb page submission:

– Email to venkat@cse.ucsc.edu• Subject: cmpe080n-assgn4

Final Exam – Last class session

• March 14, 2002

February 26, 2002 CE80N -- Lecture #15 5

Personal Web Page of the DayPersonal Web Page of the Day

A few brave souls….So, here’s:

– Robbie Stockman– Ryan Rodriguez

February 26, 2002 CE80N -- Lecture #15 7

Description Of FunctionalityDescription Of Functionality

An automated search service allows one to find information that resides on remote computers.

February 26, 2002 CE80N -- Lecture #15 8

Browsing Vs. Automated Browsing Vs. Automated SearchingSearching

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, 2002 CE80N -- Lecture #15 9

A Search Engine Helps Users A Search Engine Helps Users Get StartedGet Started

Automated searching is especially helpful when a user first begins to explore a topic.

February 26, 2002 CE80N -- Lecture #15 10

A Search Tool Can Help Recover A Search Tool Can Help Recover From LossFrom Loss

Automated search tools help users recover quickly when the location of information is lost.

February 26, 2002 CE80N -- Lecture #15 11

Automated Searching Automated Searching By NameBy Name

One can search by specific name or content.

NetScape -- search siteOverture (formerly Goto.com)

February 26, 2002 CE80N -- Lecture #15 12

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 How An Automated Search Service OperatesService Operates

Figure 25.1Figure 25.1Figure 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, 2002 CE80N -- Lecture #15 14

Modern Systems Search Web Modern Systems Search Web Page ContentsPage Contents

Users can assume the search will look for Web pages matching the topic specified.

February 26, 2002 CE80N -- Lecture #15 15

How A Web Search How A Web Search Appears To A UserAppears To A User

Search services are:– Accessed through a Web site

Search services:– Require user interaction– Use forms technology

NetScape Search Site

February 26, 2002 CE80N -- Lecture #15 16

How A Search Engine Returns How A Search Engine Returns ResultsResults

The search engine creates a Web page that has a link to each found topic.– Uses cgi technology to create pages

dynamically

February 26, 2002 CE80N -- Lecture #15 17

Automated Search Services Use Automated Search Services Use String MatchingString 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.com

February 26, 2002 CE80N -- Lecture #15 18

String MatchingString 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, 2002 CE80N -- Lecture #15 19

Advanced Search ProgramsAdvanced Search Programs

Some search engines offer multi-key search service.– Group synonyms with a common theme

together• ie, hospital doctor nurse health

February 26, 2002 CE80N -- Lecture #15 20

Advanced Services- More Advanced Services- More Sophisticated MatchingSophisticated Matching

Some services offer the opportunity to give more detailed specifications.

• Use plus sign to denote a required term

–Lycos

February 26, 2002 CE80N -- Lecture #15 21

Personalized Search ResultsPersonalized 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, 2002 CE80N -- Lecture #15 22

How An Automated Content How An Automated Content Search WorksSearch 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, 2002 CE80N -- Lecture #15 23

Searches Are RestrictedSearches Are Restricted

Automated search services search only the beginning of each page.– Use the special HTML tag:

• <META name=“my travel” content=“travel, air, sea, tickets”>

• Allows specific keywords that do not appear in the browser

– Gives the site better coverage from search engines

February 26, 2002 CE80N -- Lecture #15 24

Advertising Pays For SearchingAdvertising Pays For Searching

Web searching appears to be free.– Uses advertising to generate revenue

Example of Automated Search Example of Automated Search ServicesServices

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, 2002 CE80N -- Lecture #15 26

Significance Of Automated Web Significance Of Automated Web SearchSearch

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, 2002 CE80N -- Lecture #15 27

GlossaryGlossary

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, 2002 CE80N -- Lecture #15 28

GlossaryGlossary

Wide Area Information Server – (WAIS) An early automated search service that

permitted one to locate documents that contain key words or phrases.