Connecting to theDigital Domain

Chapter 4Exploring the Digital Domain

Connecting to theDigital Domain

basics of data communication networks how the Internet provides global connectivity how WWW is a client/server app supported

by the Internet how Web pages are hypermedia Web browser fundamentals Web directories and search engines keyword searching

In this chapter, you will learn about . . .

Data Communications Network

A collection of computer systems configured to share digital data and resources

Local Area Networks LANs extend across

limited geographical area

servers, terminals, etc.

Internetwork

collection of autonomous networks

The Internet intranets

The Internet

evolved from an experimental DOD network created in the late 1960s

decentralized loosely-coupled redundant

Internet Applications

e-mail telnet ftp (file transfer protocol) World Wide Web

World Wide Web created as a medium for disseminating

scientific research organized by Tim Berners-Lee in 1989 hypertext system

Documents with built-in cross-referencing called “hyperlinks”

open system

Client/Server CLIENT--(local)

system requesting services

SERVER--(remote) system that receives and handles requests from many clients concurrently

Web as Client/Server App Protocol--a set of rules that govern how an

activity takes place HTTP--(HyperText Transfer Protocol)

specifies how Web clients and servers communicate

URL--(Uniform Resource Locator) addressing for Web resources

HTML--(HyperText Markup Language) defines content and display of Web pages

URL Example

protocol Domain Name resource location

Web Browser (Client)

Researching on the Web Search service--generates lists of other

Web sites containing information about supplied topics

Web directory--a search service organized as a topical hierarchy and compiled by (human) editors

Search engine--search services whose databases are compiled by automated Web crawlers

Keyword Searching A form of (automated) text matching keyword--a word or phrase used as a

text pattern for matching hits--matches with text patterns misses--fails to match some or all of the

text pattern false positives--hits that are not related

to the desired topic

Boolean Expressions

search engines interpret multiple keywords as Boolean expressions

AND--intersection, i.e., references that contain both keywords

Boolean Expressions

OR--union, i.e., references that contain either keyword

Boolean Expressions

NOT--negation, i.e., references that do not contain the keyword

Mathematical Operators

Boolean Expression Mathematical Operator

Labrador AND retrievers +Labrador +retrievers

Labrador AND NOTretrievers

+Labrador -retrievers

Mathematical operators may be used to signify Boolean expressions

Hybrid Search Services metasearch engines--consult other

search engines and directories and summarize query data

niche services--commercial services targeted at a specific audience or topic

portals--gateway Web site with searching capabilities