The Internet and Information Access

The Internet and Information Access • Information resources • World Wide Web architecture • client-server • home pages • hyperlinks • HTML • CGI • Java • Search engines

The Internet • Literally, an interconnection of computer networks • with a capital I the worldwide interconnection network that uses a single defined set of communication protocols • Grew out of the ARPANet • DOD network to allow researchers to access the fastest computers in the US quickly and without travel • actually found that email was one of the most important uses (invented in 1971)

The Internet (continued) • timeline • research begun in 1966 • first sites operational in 1969 (56 Kbps) • international in 1973 • NSFNet developed in 1986 (1.5 Mbps backbone) • to connect to supercomputers! • private backbone in 1995 • 45 Mbps in 1996 • gigabit speeds being tested

The Internet (continued) • Current status • more than 10,000,000 computers directly connected worldwide • up from 500,000 in 1990 • traffic about 1 petabyte per month • growing at 6% or 7% compounded per month • simply provides a transportation medium

World Wide Web • WWW • developed at European Center for Nuclear Research (CERN) in late 1990 • sharing information on high-energy physics • uses hypertext links to different media • text, picture, video, sound, etc.

Hyperlinks Text here and some link Other text Text here and there Other text This HTML file can be ANY WHERE Text here and somelink Other text WWW is a set of hypertext files, looks like a web

World Wide Web (continued) • Web Browser and Server • graphical browsers developed in 1993 • users access WWW through a browser program • WWW client program for end user • Netscape Navigator, Microsoft Internet Explorer • browser reads/fetches files locally as well as from Internet • remote fetches come from WWW server • web browsers/ servers use IP protocols: FTP, HTTP, NNTP, ... • graphical browsers greatly enhanced accessibility of materials on the Internet

Local Disks browser Local Disks Local Disks Client - Server CERN httpd server NCSA ftp server

Web Browsers • Web browser functionalities • hyperlinks: let you point and click to access information • display: interpret HTML files based on capability of client system • often uses “helper aps” or “plugins” • active object: activate other programs • interaction: send FORM information back to server

Addressing Information • All information on the Web is accessed through addresses called Uniform Resource Locators (URLs) http://www.scu.edu/Frames/News/index.html protocol server name directory structure file

Web Home Page • Home Page • WWW hypertext document that is initial entry for some subject • Hypertext document can include • text • images • simple graphics • links to other hypertext documents • mail links

Web Home Page (continued)

HTML • HyperText Markup Language for creating a WWW page • Based on Simplified Generalized Markup Language (SGML) • In plain text and can be created using any text editor • embedded with other information in file, but distinguished by tags

HTML File <HTML> <HEAD> <TITLE>Ronald Danielson</TITLE> </HEAD> <BODY BGCOLOR="#FBF5E9"> <H1><IMG SRC="./ron2.jpg"> Ronald Danielson </H1> <HR> <P> B.A. Mathematics, (<I>summa cum laude</I>), University of Minnesota, Duluth<BR> M.S. Mathematics, Northwestern University<BR> Ph.D. Computer Science, University of Illinois at Urbana-Champaign <P> More detailed <A HREF="./cv.html">C.V.</A><BR> <HR> <P> <B>Winter Term Office Hours:</B> Monday, Wednesday, Friday 9:00 - 10:00; Monday, Wednesday 3:30 - 4:30; or by appointment. It's best to make an appointment even during office hours.<BR> <HR> <H2>What Ron spends his time on:</H2>

HTML Tags • HTML uses tags to tell the browser how to display the text • meaningful sequence of characters enclosed in < > • tags are usually paired with few exceptions • <TAG> with corresponding </TAG> • <P> is the end-of-paragraph tag and one of the exceptions • HTML tags are not case sensitive • i.e. <title> is the same as <TITLE> • Not all tags are supported by all Web browsers • browsers ignore unrecognized tags

Common HTML Tags • <Title> • browser will show bracketed text in the title bar • <Hn> • generates one of 6 levels of heading • n is replaced by a digit, 1 - 6 • with 1 begin the most prominent • smaller numbers give larger and bolder fonts • Paragraphs • only the <P> tag defines the end of a paragraph • carriage returns and white space are not significant

Common HTML Tags (continued) • Unnumbered Lists • starts with an opening list <UL> tag • enter <LI> tag followed by the individual item (no closing tag is required) • end with a closing list </UL> tag • Numbered list: ordered list • replace <UL> and </UL> by <OL> and </OL> respectively

Common HTML Tags (continued) • Preformatted text • format text exactly as typed in HTML file • use <PRE> and </PRE> tags • except for some special symbols < for < > for > & for & • Italic font <I>text in italic</I> <EM>text in emphasis</EM> <CITE>cite the text</CITE>

Common HTML Tags (continued) • Bold typeface <B>bold text</B> • Fixed width font <TT>fixed width font</TT> <CODE>fixed width font</CODE>

Linking to Other Documents • The main power of HTML • link regions of text (or image) to another document (or an image) • the hotspots are highlighted in color and underlined • use the simple hypertext-related directive A (anchor) • The syntax <A HREF=“http://www.cse.scu.edu/HCI”>COEN 1 Home page</A> In Uniform Resource Locator format

Inline Images • Different browsers allow different image files • GIF file and JPG file • usually cached: the same image only transmitted once • The syntax: <IMG SRC=“filename.gif” ALIGN=bottom ALT=“++”> Text image Text is here and aligned with figure

Inline Images (continued) • You can also anchor an image to other HTML document <A HREF=“./cv/ron.html”><IMG SRC=“my.gif” >My picture</A>

More HTML • There are a lot of additional features about HTML. One good general source is on the SCU website • http://www.scu.edu/webpublishing • Some other sources of information are: • http://www.ncsa.uiuc.edu/Indices/Resources/html-resources.html • http://www.cwru.edu/help/introHTML/toc.html • http://www.w3.org/ • the World Wide Web Consortium • viewing the source of any web page you like

More HTML (continued) • The aspects of the Web discussed so far are limited to displaying various data in various media, on command from users • one-way transfer of information • single medium display at a time • How can we have a two-way dialog? all output

CGI and HTML • Web browsing as described so far is all output • One WWW mechanism for input is an interactive form and the CGI interface in the server • What is CGI? an interface for running an external program (or gateway) under the http server cgi httpd Web site netscape form httpd

CGI and HTML Relationship • Form is part of the html files • CGI is with the http server 1. Web browser displays the form Web server 3. Submit request 4. Httpd invokes cgi program Web browser httpd cgi1 form cgi2 5. Cgi retrieves or produces a document 6. Send the result to the client 2. User fills in the form

Java • Java is designed to download to the browser machine, and execute locally • independent of type of browser machine • interpreted code so no linking • dynamically reconfigurable • multi-threaded • can do several things simultaneously • program control • can talk to server and perform independent actions • stock price updates • hockey scores • can maintain some dialog context

Java (continued) • Real programming language • cleaned-up C++ • not trivial to write • JavaScript, various development tools, class libraries and editors

Search Engines and Indices • Finding information on the Web can be difficult • Search engines and directories index material on the Web • Spiders • contact servers, scan material, index it locally • some search full text, other just subsets • titles, URLs, first 20 lines • provide capability to create queries for words from index in database • typically boolean search • rank order hits by relevancy • Google, AltaVista, Excite, Lycos, HotBot, etc.

Search Engines and Indices (continued) • Directories categorize Web content and build databases • Yahoo • Many specific search engines and directories • subject- or geographic area- specific • Meta-searchers • submit your search to several different search engines simultaneously

Some Search Engine Starting Points • URLs are case sensitive, type exactly as shown • Specific indices • http://www.yahoo.com • http://www.google.com • http://www.altavista.digital.com • http://www.excite.com • http://www.hotbot.com • General information • http://www.searchenginewatch.com

Some Web Sites to visit • All of these Web sites received awards of excellence from New Media magazine, and give you an idea of the kinds of things that can be done with Web pages • http://www.lot21.com/public/invision/edf • http://scroll.behaviour.com • http://www.imagineradio.com • http://www.discovery.com • http://www.thriveonline.com • http://www.experience.org • http://acrobat.hermanmiller.com • http://www.epgmedia.com/sprite

Some More Web Sites to visit • These sites are about technical subjects, but they also have some interesting links • http://www.intel.com/education/college/index.htm • http://www.educatorscorner.com/index.html • check “cool links” and “cartoons” • http://burks.bton.ac.uk/burks

The Internet and Information Access