01-Lecture Web System & Technology Introduction.pptx

Web Engineering

1. Web Systems & Technologies Introductory Lecture

2. Suggested Text Books: Nuckles , Craig, Web Applications: Concepts and Real World Design, Wiley 2006 Programming the World Wide Web (4th Edition) (Paperback), by Robert W. Sebesta (Author), Paperback: 752 pages, Publisher: Addison Wesley; 4th edition (August 17, 2007), ISBN-10: 0321489691 Web Application Architecture: Principles, protocols and practices by Leon Shklar and Richard Rosen, Wiley; 2nd Edition (May 5, 2009). ISBN-10 : 047051860X. 4. Web Technologies: A Computer Science Perspective by Jeffrey C . Jackson , Prentice Hall; 1st Edition (August 27, 2006). ISBN-10 : 0131856030 147. 5. Web Technologies by Uttam Kumar Roy, Oxford University Press, USA ( June 13, 2011 . 6. Google /Youtube

3. Self Learning V/S Dependent Learning…

4. WWW (World Wide Web) ? An information system on the Internet which allows documents to be connected to other documents by hypertext links, enabling the user to search for information by moving from one document to another . OR The Web, or World Wide Web, is basically a system of Internet servers that support specially formatted documents . The documents are formatted in a mark-up language called HTML (Hypertext Mark-up Language) that supports links to other documents, as well as graphics, audio, and video files . This means you can jump from one document to another simply by clicking The Web consists of pages that can be accessed using a Web browser. The Hyper-Text Transfer Protocol (HTTP) is the method used to transfer Web pages to your computer

5. WORLD WIDE WEB (Background ) During the 1980’s ,researchers at European Organization for Nuclear Research(CERN) developed the idea of “A larger Hypertext Database with typed links”. By 1990 Tim Berners Lee @ CERN had developed had developed Hyper Text Transfer Protocol (http) web browser software and web server. In 1991 the Very first web page went live on Internet with URL http ://info.cern.ch/hypertext/WWW/TheProject.html . First browser was called  WorldWideWeb  and later renamed Nexus. The first search engine created was Archie, created in 1990 by Alan Emtage , a student at McGill University in Montreal.

6. Who owns World Wide Web? The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web (abbreviated WWW or W3 ). Founded and currently led by Tim Berners-Lee, the consortium is made up of member organizations which maintain full-time staff for the purpose of working together in the development of standards for the World Wide Web . As of 2 June 2016, the World Wide Web Consortium (W3C) has 421 members.

7. Web Based System? Web-Based system refers to those applications or services that are resident on a server that is accessible using a Web browser and is therefore accessible from anywhere in the world via the Web/Internet.

8. Website? A  website  is a collection of Web pages, images, videos or other digital assets that is hosted on one or several Web server(s), usually accessible via the Internet or Local Network. The definition of  web page  is a document, typically written in HTML, Java Script, PHP which is almost always accessible via HTTP, a protocol that transfers information from the Web server to display in the user's Web browser . A web site can be found via URL(uniform resource Locator) like www.sbbusba.edu.pk

9. More about website… When was the first website created? The first web site was built at  CERN  by  Tim Berners-Lee  and put online August 6,  1991 . Should I use "website" or "web site" when writing? Most style guides suggest using "website" instead of "web site" in all forms of writing. What is the difference between a website and web page? A website refers to a central location that contains more than one web page or a series of web pages. For example, youtube.com is considered a website, which contains thousands of different web pages. Who creates websites on the Internet? Any business, government, or person can create a website on the Internet. Today, the Internet consists of billions of websites created my billions of different people.

10. Web Application A web Application is piece of software which can be accessed through browser & executed on web server. a   web application  or  web app  is a client–server software application which the client (or user interface) runs in a web browser . You don't have to install any CDs, download any software, or worry about upgrades . If you use an online bank or  web - based  email program like Gmail, Hotmail, or Yahoo Mail then you've already used  web - based  software before . Web application are created using language tools like HTML,CSS,JavaScript,PHP,Ajax .

11. What is URL? URL is the abbreviation of Uniform Resource Locator . URL is the global address of documents and other resources on the World Wide Web . Example: http://www.sbbusba.edu.pk The first part of the URL is called a  protocol identifier  and it indicates what protocol to use, and the second part is called resource name  and it specifies the domain name where the resource is located . The protocol identifier and the resource name are separated by a colon and two forward slashes. For example, the two URLs below point to two different files at the domain  webopedia.com .  The first specifies an  executable file  that should be fetched using the FTP protocol; the second specifies a Web page that should be fetched using the HTTP protoco l : ftp://www.webopedia.com/stuff.exe   http://www.webopedia.com/index.html

12. Web Browser Web browser, a browser is a software application used to locate, retrieve and display content on the World Wide Web, including Web pages, images, video and other files . As a client/server model, the browser is the client run on a computer that contacts the Web server and requests information . The Web server sends the information back to the Web browser which displays the results on the computer or other Internet-enabled device that supports a browser . Today's browsers are fully-functional software suites that can interpret and display HTML Web pages, applications,  JavaScript, AJAX  and other content hosted on Web servers. Many browsers offer plug-ins which extend the capabilities of the software so it can display multimedia information (including sound and video), or the browser can be used to perform tasks such as videoconferencing, to design web pages or add anti-phishing filters and other security features to the browser.

13. Web Server On the hardware side, a web server is a computer that stores a website's component files (e.g. HTML documents, images, CSS stylesheets, and JavaScript files) and delivers them to the end-user's device. It is connected to the Internet and can be accessed through a domain name like facebook.com On the software side, a web server includes several parts that control how web users access hosted files, at minimum an HTTP server. An HTTP server is a piece of software that understands URLs (web addresses) and HTTP (the protocol your browser uses ito vew webpages). At the most basic level, whenever a browser needs a file hosted on a web server, the browser requests the file via HTTP. When the request reaches the correct web server (hardware), the HTTP server (software) sends the requested document back, also through HTTP. Most leading servers are like APACHE,IIS(Internet Information server) etc.

14. Client Server Architecture

15. Example of Client Server Architecture

16. “Evolution Web Web 1.0 It is the “readable” phrase of the World Wide Web with flat data. In Web 1.0, there is only limited interaction between sites and web users. Web 1.0 is simply an information portal where users passively receive information without being given the opportunity to post reviews, comments, and feedback. Web 2.0 It is the “writable” phrase of the World Wide Web with interactive data. Unlike Web 1.0, Web 2.0 facilitates interaction between web users and sites, so it allows users to interact more freely with each other . Web 2.0 encourages participation, collaboration, and information sharing. Examples of Web 2.0 applications are Youtube , Wiki, Flickr, Facebook, and so on . Web 3.0 It is the “executable” phrase of Word Wide Web with dynamic applications, interactive services, and “machine-to-machine” interaction. Web 3.0 is a semantic web which refers to the future. In Web 3.0, computers can interpret information like humans and intelligently generate and distribute useful content tailored to the needs of users . One example of Web 3.0 is Tivo , a digital video recorder. Its recording program can search the web and read what it finds to you based on your preferences.

17. DNS Short for Domain Name System (or Service or Server), an Internet service that translates domain names into IP addresses. Because domain names are alphabetic, they're easier to remember. The Internet however, is really based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.example.com might translate to 198.105.232.4. The DNS system is, in fact, its own network. If one DNS server doesn't know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.

18. DNS (Continued…)

19. HTTP HTTP (Hypertext Transfer Protocol)  provides a network protocol standard that Web browsers and servers use to communicate . Tim Berners-Lee created the initial HTTP in the early 1990s. HTTP has different versions like HTTP 0.9  ,1.0,1.1,2.0. HTTP is an application layer protocol built on top of TCP that uses a client-server communication model. H TTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted , and what actions Web servers  and browsers  should take in response to various commands . For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page.

20. Basic Features HTTP is connectionless: The HTTP client, i.e., a browser initiates an HTTP request and after a request is made, the client disconnects from the server and waits for a response. The server processes the request and re-establishes the connection with the client to send a response back. HTTP is media independent: It means, any type of data can be sent by HTTP as long as both the client and the server know how to handle the data content . It is required for the client as well as the server to specify the content type using appropriate MIME-type. HTTP is stateless: As mentioned above, HTTP is connectionless and it is a direct result of HTTP being a stateless protocol . The server and client are aware of each other only during a current request. Afterwards , both of them forget about each other. Due to this nature of the protocol, neither the client nor the browser can retain information between different requests across the web pages. This shortcoming of HTTP is being addressed in a number of new technologies, including ActiveX, Java, JavaScript and cookies.

21. HTTP Status Codes are Error Messages Errors on the Internet can be quite frustrating — especially if you do not know the difference between a 404 error and a 502 error. These error messages, also called HTTP status codes are response codes given by Web servers and help identify the cause of the problem . For example, "404 File Not Found" is a common HTTP status code. It means the Web server cannot find the file you requested. This means the webpage or other document you tried to load in your Web browser has either been moved or deleted, or you entered the wrong URL or document name.

22. HTTP Method… GET : The GET method is used to retrieve information from the given server using a given URI. Requests using GET should only retrieve data and should have no other effect on the data . POST : A POST request is used to send data to the server, for example, customer information, file upload, etc. using HTML forms . PUT : Replaces all current representations of the target resource with the uploaded content . DELETE : Removes all current representations of the target resource given by a URI .