Full HTML for

Basic foilset Introduction to World Wide Web (WWW)

Given by Nancy J. McCracken at ECS400 Senior Undergraduate Course on Spring Semester 97. Foils prepared 11 May 1997
Outside Index Summary of Material

The World Wide Web is a world-wide repository of linked information, called hypertext or hypermedia. It consists of
  • A user interface consistent across many computers
  • A set of open standards that enables the interface to access a variety of document types and information protocols.
  • A provision for universal access, based on the Internet domain name schemes.
In this talk, we give a brief background on the Internet and its services (telnet, ftp, news and mail), Client/Server Architectures, Networking, and several prominent Web technologies.
This is an introductory talk intended for people of any background who have used the Web, but wish to know more about how it works and what capabilities are possible.

Table of Contents for full HTML of Introduction to World Wide Web (WWW)

 Denote Foils where Image Critical
Denote Foils where HTML is sufficient
1 Introduction to the World Wide Web (WWW)
and Web Technologies
2 Introduction to the World Wide Web
3 Background on the Internet
4 History of the Internet
5 History of the World Wide Web
6 Applications based on information services typically use a Client/Server Architecture
7 Familiar Clients and Servers
8 The World Wide Web is a collection of clients and servers called browsers and Web sites
9 Networking
10 Internet Services: Telnet
11 Internet Services: FTP
12 Internet Services: News
13 Internet Services: Mail Lists
14 Web Content is Hyperlinked Multimedia
15 Web Links can go to other Internet Services
16 Multimedia types
17 Forms and CGI Scripting
18 The CGI script returns data through the server
19 Web Search Engines
20 Web Search Indexes
21 Databases
22 JavaScript
23 Java
24 Future Web Technologies: VRML

Outside Index Summary of Material

HTML version of Basic Foils prepared 11 May 1997

Foil 1 Introduction to the World Wide Web (WWW)
and Web Technologies

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Dr. Nancy McCracken
NPAC
Syracuse University
December 9, 1996
HTML version of Basic Foils prepared 11 May 1997

Foil 2 Introduction to the World Wide Web

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
The World Wide Web is a world-wide repository of linked information, called hypertext or hypermedia. It consists of
  • A user interface consistent across many computers
  • A set of open standards that enables the interface to access a variety of document types and information protocols.
  • A provision for universal access, based on the Internet domain name schemes.
In this talk, we give a brief background on the Internet and its services (telnet, ftp, news and mail), Client/Server Architectures, Networking, and several prominent Web technologies.
This is an introductory talk intended for people of any background who have used the Web, but wish to know more about how it works and what capabilities are possible.
HTML version of Basic Foils prepared 11 May 1997

Foil 3 Background on the Internet

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
The Internet is a loose federation of networks.
Cooperative organization - no administration, no fees. Protocols and standards are evolved through the IETF, Internet Engineering Task Force.
Most national and international networks are members: NSFNET, ESNET, ARPANET, BITNET
All these networks are packet switched systems based on TCP/IP. Together these protocols allow for communication over a wide variety of technologies. Machines called gateways connect the networks.
Standard domain name system - names are looked up by name server to obtain routing information.
  • symbolic names: npac.syr.edu
  • internet addresses: 128.230.7.2
HTML version of Basic Foils prepared 11 May 1997

Foil 4 History of the Internet

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
1969 The first locations commissioned by DOD (ARPA)
1971 # host computers = 23
1982 Standards for TCP and IP established.
1983-4 Name server and domain name server developed.
1984 #host computers > 1,000
1986 NSFNET backbone established, 56Kbps
1987 #host computers > 10,000
1989 NSFNET backbone upgraded to T1 (1.544Mbps)
  • #host computers > 100,000
1992 Internet Society is chartered, World Wide Web released by CERN
  • NSFNET backbone upgraded to T3 (44.736Mbps)
    • #host computers > 1,000,000
1993 NSF experiments with 600 Megabit backbone
  • #host computers > 2,000,000
HTML version of Basic Foils prepared 11 May 1997

Foil 5 History of the World Wide Web

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
1990 Tim Berners-Lee at CERN in Geneva implements a hypertext system to provide efficient information access to the members of the international high-energy physics community.
1993 Marc Andreessen at NCSA at the University of Illinois develops a graphical user interface.
1994 Web Servers increase by 10% per month.
1994 World Wide Web Consortium formed to guide the technical development of standards. The Consortium is run for the Laboratory of Computer Science at MIT, CERN, and INRIA (the French Research Institute).
1995 Netscape Communications Corp., founded by Mark Andreessen, offers many extensions in its browser.
1995 Commercial interest in the web grows. Prodigy, Compuserver and America On-line offer Web access to the public.
1996 The Web is integrated with other computing technologies such as databases. Secure web commerce has still not yet arrived.
HTML version of Basic Foils prepared 11 May 1997

Foil 6 Applications based on information services typically use a Client/Server Architecture

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Server: A program in charge of a resource or information.
  • Operation is defined by list of services.
  • Normal mode is to listen for requests, stopping to fulfill a request when it arrives.
Client: Any program that makes a request for service from the server.
HTML version of Basic Foils prepared 11 May 1997

Foil 7 Familiar Clients and Servers

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Clients and servers send their messages over a network connection.
HTML version of Basic Foils prepared 11 May 1997

Foil 8 The World Wide Web is a collection of clients and servers called browsers and Web sites

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Web servers provide access to a collection of files containing hyperlinked information
  • primary service is to send text files, images, digitized video
  • can also provide customized services through the form/CGI script interface
Browsers provide an easy graphical interface for users to request information. The client machine also provides viewers for a standard set of image and video formats.
The interface is kept very simple to run on all networks and most machines.
HTML version of Basic Foils prepared 11 May 1997

Foil 9 Networking

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
The Internet is a packet-switched network. Each message (or document) is broken up into a number of packets. Each packet has an address. A computer called a router sits on the local network and decides where to send it first on its way to its final address. Each computer along the network connection examines messages that come in and either keeps it or reroutes it along its way. The message is reassembled on the other end.
Performance of network delivery depends on the size of the message, the capacity of the various pieces of network that the message may travel along and the congestion of the network.
HTML version of Basic Foils prepared 11 May 1997

Foil 10 Internet Services: Telnet

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Telnet basically allows you to log in to a system over a network just as though you were logging in from a terminal attached to the system or from a dial-up modem.
You may use telnet from a command line such as:
    • > telnet nova.npac.syr.edu
where you give the internet name of the machine that you wish to connect to. The telnet service will proceed to ask you for a name and password just as if you were logging in.
Or you may have a telnet program which prompts you for the same information.
Between two unix systems, you can use the rlogin command instead.
Mostly, you must already have an account on the machine to log in. There are a few publicly available telnet machines, such as the FAA Flight Service at duats.gtefsd.com, where student pilots can log in to get the latest weather data.
HTML version of Basic Foils prepared 11 May 1997

Foil 11 Internet Services: FTP

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
FTP (File Transfer Protocol) is the way that people transfer files from one internet machine to another.
You can use the ftp protocol directly from Unix machines using a command line:
    • > ftp internethostmachinename
where it will prompt you for an account login name and password. You will then be connected to the home directory of that account and can use commands to move around the directory structure (cd and ls) and commands get and put to copy a file to or from your original location.
Other ftp interfaces may be provided by your telnet program, or by other software programs such as fetch.
FTP will transfer files of all types and formats. If the files are large, such as images, you may want to transfer in binary mode (the default is ascii).
Some machines may provide a special ftp account called "anonymous". You use your ftp program as usual, except that the login name is "anonymous". The password can be anything, but netiquette obliges you to give your email address. The directory that you are connected to is a public directory provided by the host machine.
HTML version of Basic Foils prepared 11 May 1997

Foil 12 Internet Services: News

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Usenet newsgroups provide discussion forums on a wide range of topics. You can read the forums from a news server installed at your site.
The topics are organized into hierarchies. Some of the main categories are
  • alt - alternative topics
  • comp - computers and computing
  • misc - miscelleneous newsgroups
  • rec - recreational topics
  • sci - science-related topics
  • soc - social and cultural topics
Subtopic names are always shown as part of the hierarchy
  • sci.chem.electrochem and comp.parallel
People participate in newsgroups by contributing messages, called "posting", which everyone else on the list can read.
Some newsgroups are moderated, which means that posted messages are scanned by a human for appropriate content and style before being made public.
Many software packages are news readers, including Netscape web browsers - just ask your systems administrator what news server to use.
HTML version of Basic Foils prepared 11 May 1997

Foil 13 Internet Services: Mail Lists

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Other discussion forums on interesting topics are provided through mail lists. The discussion is delivered through your regular email.
In this case, the discussion is again provided through messages. But instead of posting the message through special software (as is the case with news readers), the message is sent to an email address, and then forwarded to everyone in the group.
Mail list addresses
  • Posting address listname@host
    • post messages by sending them to this email address
  • Adminstrative address listname-request@host
    • use this email address to subscribe and unsubscribe to a list.
  • List owner listname-owner@host
Mail lists may also be moderated.
HTML version of Basic Foils prepared 11 May 1997

Foil 14 Web Content is Hyperlinked Multimedia

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
The World Wide Web is a collection of documents located all over the world, and which can have links to images, motion videos and audio files.
Links use Web addresses called URL's (Uniform Resource Locators) which have the form
  • http://www.place.org:8888/mydirectory/mydoc.html
where
  • http is the hyperlink web service
  • www.place.org is the internet name of the web server
  • 8888 is the optional port number
  • /mydirectory/ is the directory or folder path to the document within the web server document space
  • mydoc.html is the document to be retrieved (with an html file extension)
Types of files follow the standard MIME (Multipurpose Internet Mail Extensions) originally developed to include multimedia and multi-part content with electronic mail messages.
File extensions on the server tell which MIME format the file is in.
The browser is configured to have a set of helper applications or "plug-ins" to appropriately display or play files in various MIME formats.
HTML version of Basic Foils prepared 11 May 1997

Foil 15 Web Links can go to other Internet Services

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Web servers provide what is called HTTP service (for HyperText Transfer Protocol), but links can also direct connections to other Internet services.
For other services, the Web server transfers the connection to the appropriate server.
HTML version of Basic Foils prepared 11 May 1997

Foil 16 Multimedia types

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Image types:
  • GIF - Color image format where each pixel is represented from 1-8 bits. Compressed to a very compact size for images with not many colors.
  • JPEG - Color image format where each pixel represented by 24 bits, giving so-called "true color". Also compressed for reasonable sizes of images with high-resolution, photographic quality.
  • PNG - new portable networks graphics format designed for web
Audio types:
  • Basic audio types are au and snd, supported by most audio players. The entire audio file is downloaded before it is played.
  • RealAudio - ram - a format which allows the plug-in to play the audio file as it is downloaded.
Video types:
  • Quicktime - Apple video format supports synchronized audio and video and has compression schemes.
  • MPEG - is most videly used but is not synchronized. Compression scheme records differences between frames.
  • Motion JPEG
HTML version of Basic Foils prepared 11 May 1997

Foil 17 Forms and CGI Scripting

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Forms are used to allow the user to send information from the browser back to the server.
The server must provide a program, called a CGI script, that will process the user information and provide an appropriate response.
  • The information from the form is encoded in a message according to the Common Gateway Protocol and sent to the web server, along with the URL of the CGI script.
  • The server executes the CGI script, passing the encoded information.
HTML version of Basic Foils prepared 11 May 1997

Foil 18 The CGI script returns data through the server

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
The CGI program parses the input from the server and performs any number of computing and data access functions:
  • looking up information in files on the server or in server databases.
  • performing computions or communicating with other machines.
  • returning already prepared documents or other multimedia files.
  • returning a document prepared "on-the-fly"
When the CGI program terminates, the server closes the connection.
HTML version of Basic Foils prepared 11 May 1997

Foil 19 Web Search Engines

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Search Engines enable users to look up text documents stored on the Web, usually by one or more keywords appearing in the document.
Information gathering and filtering
  • This is done by web "robots" - programs which automatically connect to all servers and search some number of documents - usually up to a certain "depth" of links, such as 4.
  • For each document, the robot returns keywords and other information to the search index. For example, Lycos returns: the title, any headings and subheadings, the 100 most"weighty" words, the first 20 lines, the size in bytes, and the number of words.
  • Problems with information gathering:
    • Information update
    • Information resulting from CGI scripts is not available.
    • Resource intensive: robots repeatedly connect to a site, informal protocols try to prevent "rapid fire" or "robot attack"
    • Preventing robot loops when links are circular.
HTML version of Basic Foils prepared 11 May 1997

Foil 20 Web Search Indexes

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Indexing: the information gathered by the robots is organized into an indexing database at the search server.
  • Primarily keyword indexing is currently used - some full text searching is just on single site search engines.
  • Key issue is size of resulting database.
Searching: the indexing database allows (keyword) searches by the user.
  • Queries are formed, some number of most highly ranked results are returned.
User Interface
  • uniform interface for HTTP, FTP, GOPHER, WAIS, Harvest, Lycos
Challenge of WWW search:
  • estimated total size is 30 Gigabytes, 5 million documents (many search engines now take months to crawl the web to update index files.)
  • diversity - huge distributed database, unstructured, non-relational, hierarchical information with many formats.
HTML version of Basic Foils prepared 11 May 1997

Foil 21 Databases

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Many useful Web applications provide a web page interface to a commercial product database of information.
This is currently done through CGI scripting.
The database must have a programmable interface (in addition to an interactive interface). For relational databases, this has been standardized in the query language SQL.
Web queries to the database are taken from an HTML form, the information is passed to the CGI script, which makes appropriate SQL queries to the database. The results of the database query can be formatted and returned to the web page.
HTML version of Basic Foils prepared 11 May 1997

Foil 22 JavaScript

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Developed by Netscape from HTML scripting language LiveScript, and including some features of Java, that allows HTML authors to have more control over the behavior of the browser.
JavaScript is text embedded in an HTML document using the <SCRIPT> tags, which a JavaScript browser will interpret (and other browsers ignore).
JavaScript can perform animations, respond to buttons and other forms of user input, and allow the author more control over the appearance of the Web Page.
JavaScript can also provide an object-oriented view of other browser plug-in programs.
Reference: JavaScript Authoring Guide at http://home.netscape.com/eng/mozilla/Gold/handbook/javascript/
HTML version of Basic Foils prepared 11 May 1997

Foil 23 Java

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
Java is a general-purpose object-oriented language developed by Sun with the capability of providing distributed computing through the Web (http://www.javasoft.com).
Browsers (HotJava, Netscape 2.0/3.0 ..) supporting Java allow arbitrarily sophisticated dynamic multimedia applications inserts called Applets, written in Java, to be embedded in the regular HTML pages and activated on each exposure of a given page.
HTML version of Basic Foils prepared 11 May 1997

Foil 24 Future Web Technologies: VRML

From Introduction to World Wide Web (WWW) ECS400 Senior Undergraduate Course -- Spring Semester 97. *
Full HTML Index
VRML is a computer graphics language for describing 3-Dimensional scenes. It was developed as a standard for the WWW from OpenInventor of SGI.
VRML includes language elements for creating simple shapes, various lighting effects, applying textures to shapes, and various points of view (referred to as cameras).
A VRML enabled browser will recogize VRML files of the form file.wrl, and create an interface where the user has controls to fly through space and examine objects.
Objects within a VRML scene may be configured as URL links to other Web pages of any document type.
VRML documents are huge - most serious current drawback to using VRML more widely on the Web is the slow download time.
New versions of VRML include motion in the scenes.
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