Internet Technologies_1. Doc. Ing. František Huňka, CSc.

Transcription

1 1 Internet Technologies_1 Doc. Ing. František Huňka, CSc.

2 Outline of the Course 2 Internet and www history. Markup languages. Software tools. HTTP protocol. Basic architecture of the web systems. XHTML 1 Web browsers. XHTML 2 Cascading style sheets JavaScript 1 JavaScript 2 XML Databases on the web. Web servers. PHP 1 PHP 2

3 Outline 3 Internet and Web History Markup languages history and meaning Software tools servers browsers script languages database systems HTTP protocol Basic Web Architecture XHTML

4 Internet and Web History 4 early 60-ties USA first ideas of computer net connecting governmental, military and university computers early 90-ties spreading into commercial sphere original idea make communication faster and easy using s 1992 first graphical browsers that enable picture display attached to the text information fast development all over the world

5 What is WWW 5 WWW is graphical, hypertext based information system that enables access to the lots of means on the Internet Tim Berners-Lee (CERN, father of WWW) designed WWW structure and created the first web browser on the NeXT working station -1989

6 Attributes Creating WWW 6 support for different protocols (HTTP, FTP) access to hypertext information (references) distributed information ( jump from one computer to another unrestricted computer space) graphical user interface (GUI) multimedia properties (video, sound -playing) interactive access (dialog forms) dynamic update (always latest versions) support different target platforms (Unix, Windows, Macintosh)

7 How WWW Works 7 web information stored on web pages web pages are files stored on computer called web server computers that read pages are called web clients clients that view (examine) pages through the program called web browser

8 WWW Work Scheme 8 HTTP Protocol request (URL) Client answer (HTML) Server Data

9 W3C (World Wide Web Consortium) 9 created in 1994 for checking WWW standards and WWW protocol development created by 450 member organization all over the world try to coordinate development and future orientation WWW in the field of networks, graphics, user interface by introducing general set of protocol issue standards and proposals for HTML, XHTML, CSS,.. more information on

10 Markup Languages History 10 GML (General Markup Language) SGML (Standard Generalized Markup Language) HTML (Hypertext Markup Language) XML (extensiblemarkup Language) XSLT (extensiblestylesheet Language Transformations)

11 SGML 11 approved by ISO in 1986 meta language facilitating for other language definition enables own definition of markup languages using DTD (Document Type Definition)

12 HTML Hypertext Markup Language 12 this language enables to separate text into several logical levels, use several types of text emphasizing and put references and pictures into the text 1995 standard HTML 3.0 (small support of browsers) XHTML (extensiblehypertext Markup language) compensation for HTML 4.01 in XML CSS (Cascading Style Sheets) enables to define manners for a single element display

13 XML (extensible Markup Language) 13 first version in 1998 created as a subset of SGML maintaining own marks definition possibility using DTD (Document Type Definition) extended for international language support place emphasis on understandability and easy work with data XML does not replace HTML, XML will be used for description and data transmission while HTML will be used for data display

14 XSLT (extensible Stypesheet Language Transformation) 14 language for transformation Web in the future will need transfer data in different formats through different browsers and servers XSLT is a new standard serving for data transformation into different formats is capable to add, erase, change elements and decide, which elements display

15 Software Tools Script languages 2. Database systems 3. Web browsers 4. Editors

16 Script Languages 16 two kinds of scripts server sided includes (SSI) CGI (Common Gateway Interface) scripts The scripts must be supported by the server they are running on written in shell, Perl, PHP, Java..

17 Server Side Includes 17 commands of the script are combined with the text of the page before sending to the client, all script commands are evaluated and the result of evaluation is placed on the adequate place on the page evaluation is in charge of WWW server browser accepts current page e.g. in HTML ex.: ASP (Active Server Pages), PHP (Professional Home Page)

18 CGI Common Gateway Interface 18 programs written in an arbitrary programming language compiled into an executable form server, which receives the program as an URL reference, runs (executes) the program and gives the result to the browser as a reply

19 Database systems 19 Database is a place for storing all needed data The stored data are accessible through DBMS (Database Management System) Data are arranged in the database using relational model in the forms of tables e.g. a table with personal data of students. Rows corresponds to individual students, columns corresponds to individual data attributes

20 Web browsers 20 Means to communicate with WWW It is a program, which enable to get to any kind of information on any computer attached into Internet and display the information in recognizable form. The only thing it needs to know is where the information is located. Mind the fact! The same page can be displayed in a different way on a different browsers. e.g. Explorer, Mizila, FireFox, Opera, Netscape

21 Web browsers II 21 web page creator has two possibilities how create web pages: create standard pages, that are displayed in all browsers good optimized pages for one browser and hope the page will be displayed good also by other browsers URL (Uniform Resource Locator) an address that tells the browser where to locate (find) information sources protocol://domain name/directory/file name

22 Editors 22 text editors like a notepad structured editors WYSIWYG Editors EditPlus, PSpad, UltraEdit

23 WYSIWYG editors what you see is what you get 23 formatted text by style is seen, single tags are not seen most of the editors enable direct changes in the code advantage comfort work, disadvantage possible mess in the code examples: FrontPage, Dreamweaver, Adobe, GoLive

24 Basic Architecture of Web Servers 24 What the web server is What the web server should be Apache SSI

25 What the web server is 25 it is a program running on the computer connected to the Internet, which waits for some web browser to attach and asks a program for its services server look up what browser needs, sends the browser back required files together with information what kind of files they are so that the browser can decide how to display received files communicates using HTTP protocol runs scripts (CGI) and programs

26 What the Web Server Should Be 26 fast so that it could be capable to work as many as requirements multitasking so that it could work more requirements in the same time capable check users authenticity and different levels of their authorization capable to agree with the applicant on style and language of the response offering different formats safe

27 Apache 27 originally designed for Unix powerful and stable server free support many modern technologies about 65% of www servers use Apache

28 Server Side Includes 28 this technology starts spreading in time of CGI scripts simple commands placed into HTML page in a special format (with *.shtml extension), which web server executes before sending the page to the browser optimally used foremost with large servers requiring standard headers and footings