CHAPTER 1 Internet & World Wide Web
Topics • A Brief Introduction to the Internet • The World Wide Web • Web Browsers • Web Servers • Uniform Resource Locator • Tools and Web Programming Languages
Learning Outcomes At the end of this lesson, students should be able to: • Understand history and concepts related to Internet and World Wide Web. • Understand a number of tools and web programming languages that are used in web development.
A Brief Introduction to the Internet Origins • ARPAnet - late 1960s and early 1970s. • For ARPA-funded research organizations. • BITnet, CSnet - late 1970s & early 1980s. • Was built for email and file transfer for other institutions.
A Brief Introduction to the Internet • NSFnet - 1986 • Originally for non-DOD funded places. • Initially connected five supercomputer centers. • By 1990, it had replaced ARPAnet for non- military uses. • Soon became the network for all (by 1990). • NSFnet eventually became known as the Internet.
A Brief Introduction to the Internet What the Internet Is • A world-wide network of computer networks. • At the lowest level, since 1982, all connections use TCP/IP. • TCP/IP hides the differences among devices connected to the Internet. • Internet is actually a network of networks rather than a network of computers.
A Brief Introduction to the Internet IP Address • Every node has a unique numeric address. • Form: 32-bit binary number. • Usually written as four 8-bit numbers, separated by periods. • Example: 18.104.22.168 8 bits 8 bits 8 bits 8 bits
A Brief Introduction to the Internet • New standard, IPv6, has 128 bits (1998) • Organizations are assigned groups of IPs for their computers. • Example: A small organization may be assigned 256 IP addresses, such as 22.214.171.124 to 126.96.36.199.
A Brief Introduction to the Internet Domain • Form: host-name.domain-names • First domain is the smallest; last is the largest. • Last domain specifies the type of organization. • Fully qualified domain name - the host name and all of the domain names.
A Brief Introduction to the Internet • Example: www.arwen-undomiel.com/misc/dict.html arwen-undomiel.com is a domain name of above web site. www is the host. • DNS servers - convert fully qualified domain names to IPs.
The World Wide Web Origins • Tim Berners-Lee at CERN proposed the Web in 1989. • Purpose: to allow scientists to have access to many databases of scientific work through their own computers.
The World Wide Web • Hypertext- text with embedded links to text in other documents to allow non-sequential browsing of textual material. • Hypermedia – more than just text – images, sound, etc.
Web Browser • Mosaic - NCSA (Univ. of Illinois), in early 1993. • First to use a GUI, led to explosion of Web use initially for X-Windows, under UNIX, but was ported to other platforms by late 1993. • Browsers are clients - always initiate, servers react (although sometimes servers require responses).
Web Browser • Most requests are for existing documents, using HyperText Transfer Protocol (HTTP). • But some requests are for program execution, with the output being returned as a document. • Example of web browsers: Netscape, Opera, Internet Explorer, Mozilla, Firefox, Google Chrome, Safari.
Web Server • Provide responses to browser requests, either existing documents or dynamically built documents. • Example of web server: Apache, Microsoft Internet Information Server.
Uniform Resource Locator (URL) The Structure of URLs • Taking http://www.mydomain.net/~rdralph/rdralph/ as an example.
Uniform Resource Locator (URL) Common Internet Protocols • There are several protocols used commonly on the Internet to get to a variety of sites which support them. • The protocol which supports the World Wide Web - just one component of the Internet - is http - hypertext transfer protocol.
Uniform Resource Locator (URL) Common Internet Protocols
Uniform Resource Locator (URL) Common Internet Protocols
Uniform Resource Locator (URL) Host Domain Names • Form of host domain names: • The Location name is almost always mnemonic - an abbreviation of the location name or an acronym for it. • A lot of the time the location name is not abbreviated at all.
Uniform Resource Locator (URL) • The domain can tell us what type of site we can expect to be visiting. Common Domain Acronyms
Uniform Resource Locator (URL) • Some sites use a geographical approach in their domains. • The last two positions in the domain of a WWW site outside the US often represents the country. • Universal two-letter country codes are used. For example: my= Malaysia, sa = Saudi Arabia, uk = The United Kingdom, sg = Singapore
Uniform Resource Locator (URL) Paths in URLs • The tilde (~) generally precedes the name of a directory assigned to a person. • In the URL http://metalab.uniten.edu.my/~mia, for example, the mia part indicates an account name associated with the author mia.
Tools and Web Programming Languages HTML • To describe the general form and layout of documents. • An HTML document is a mix of content and controls. • Controls are tags and their attributes.
Tools and Web Programming Languages • Tags often delimit content and specify something about how the content should be arranged in the document. • Attributes provide additional information about the content of a tag.
Tools and Web Programming Languages XML • A meta-markup language. • Used to create a new markup language for a particular purpose or area. • Because the tags are designed for a specific area, they can be meaningful. • No presentation details. • A simple and universal way of representing data of any textual kind.
Tools and Web Programming Languages Java • General purpose object-oriented programming language. • Based on C++, but simpler and safer. • Focus is on applets and servlets.
Tools and Web Programming Languages Perl • Provides server-side computation for HTML documents, through CGI. • Perl is good for CGI programming because: • Direct access to operating systems functions • Powerful character string pattern-matching operations • Access to database systems
Tools and Web Programming Languages • Perl is highly platform independent, and has been ported to all common platforms. • Perl is not just for CGI.
Tools and Web Programming Languages Tools for Creating Web Page • Adobe Dreamweaver (Latest version CS4) • Microsoft Front Page • Adobe PageMill
Other info • Machines running specialized software called web sever store XHTML documents. • Netscape and Internet Explorer are the two most popular Web browsers. • ASP.NET is not an example of a platform-independent technology. • Authentication is commonly done through the use of logon password. • Authorization is the process of giving someone permission to do or have something • Logically, authorization is preceded (headed) by authentication.
One of the most common security measures available to protect E-commerce sites is SSL • Lack of faith in E-Commerce site security is cited as the most common reason why people refuse to shop online. • FTP is the acronym for File Transfer Protocol. • HTTPS is the same way as HTTP but used securely. • WWW introduced in 1990 by Tim Berners-Lee. • An Internet Service Provider is a company that provides individuals and other companies access to the Internet and other related services. • A client is the requesting program in a client/server relationship.
References • Programming the World Wide Web, Second Edition Author: Robert W. Sebesta Publisher: Addison-Wesley • NetStrider Tutorial: Uniform Resource Locators <http://www.netstrider.com/tutorials/URL/> Last accessed: 22nd June 2009