Uniform Resources Locators In the Web,functionality of pointers is provided by Uniform Resource Locators (URLs). URL example: http://www.acm.org/sigmod The first part indicates how the document is to be accessed "http"indicates that the document is to be accessed using the Hyper Text Transfer Protocol. The second part gives the unique name of a machine on the Internet. The rest of the URL identifies the document within the machine. The local identification can be: The path name of a file on the machine,or An identifier(path name)of a program,plus arguments to be passed to the program -E.g.,http://www.google.com/search?q=silberschatz Database System Concepts-6th Edition 9.7 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 9.7 ©Silberschatz, Korth and Sudarshan th Edition Uniform Resources Locators In the Web, functionality of pointers is provided by Uniform Resource Locators (URLs). URL example: http://www.acm.org/sigmod The first part indicates how the document is to be accessed “http” indicates that the document is to be accessed using the Hyper Text Transfer Protocol. The second part gives the unique name of a machine on the Internet. The rest of the URL identifies the document within the machine. The local identification can be: The path name of a file on the machine, or An identifier (path name) of a program, plus arguments to be passed to the program – E.g., http://www.google.com/search?q=silberschatz
HTML and HTTP HTML provides formatting,hypertext link,and image display features including tables,stylesheets(to alter default formatting),etc. HTML also provides input features Select from a set of options -Pop-up menus,radio buttons,check lists Enter values -Text boxes Filled in input sent back to the server,to be acted upon by an executable at the server HyperText Transfer Protocol(HTTP)used for communication with the Web server Database System Concepts-6th Edition 9.8 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 9.8 ©Silberschatz, Korth and Sudarshan th Edition HTML and HTTP HTML provides formatting, hypertext link, and image display features including tables, stylesheets (to alter default formatting), etc. HTML also provides input features Select from a set of options – Pop-up menus, radio buttons, check lists Enter values – Text boxes Filled in input sent back to the server, to be acted upon by an executable at the server HyperText Transfer Protocol (HTTP) used for communication with the Web server
Sample HTML Source Text <html> <body> <table border> <tr><th>ID</th><th>Name</th><th>Department</th></tr> <tr><td>00128</td><td>Zhang</td><td>Comp.Sci.</td></tr> </table> <form action="PersonQuery"method=get> Search for: <select name="persontype"> <option value="student"selected>Student </option> <option value="instructor">Instructor </option> </select><br> Name:<input type=text size=20 name="name"> <input type=submit value="submit"> </form> </body></html> Database System Concepts-6th Edition 9.9 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 9.9 ©Silberschatz, Korth and Sudarshan th Edition Sample HTML Source Text <html> <body> <table border> <tr> <th>ID</th> <th>Name</th> <th>Department</th> </tr> <tr> <td>00128</td> <td>Zhang</td> <td>Comp. Sci.</td> </tr> …. </table> <form action="PersonQuery" method=get> Search for: <select name="persontype"> <option value="student" selected>Student </option> <option value="instructor"> Instructor </option> </select> <br> Name: <input type=text size=20 name="name"> <input type=submit value="submit"> </form> </body> </html>
Display of Sample HTML Source ID Name Department 00128 Zhang Comp.Sci. 12345 Shankar Comp.Sci. 19991 Brandt History Search for: Student Name: submit Database System Concepts-6th Edition 9.10 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 9.10 ©Silberschatz, Korth and Sudarshan th Edition Display of Sample HTML Source
Web Servers A Web server can easily serve as a front end to a variety of information services. The document name in a URL may identify an executable program,that,when run,generates a HTML document. When an HTTP server receives a request for such a document,it executes the program,and sends back the HTML document that is generated. The Web client can pass extra arguments with the name of the document. To install a new service on the Web,one simply needs to create and install an executable that provides that service. The Web browser provides a graphical user interface to the information service. Common Gateway Interface(CGl):a standard interface between web and application server Database System Concepts-6th Edition 9.11 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 9.11 ©Silberschatz, Korth and Sudarshan th Edition Web Servers A Web server can easily serve as a front end to a variety of information services. The document name in a URL may identify an executable program, that, when run, generates a HTML document. When an HTTP server receives a request for such a document, it executes the program, and sends back the HTML document that is generated. The Web client can pass extra arguments with the name of the document. To install a new service on the Web, one simply needs to create and install an executable that provides that service. The Web browser provides a graphical user interface to the information service. Common Gateway Interface (CGI): a standard interface between web and application server