Choosing Software The requirements of the application call
Choosing Software The requirements of the application call for the application to be web-based, with a WML front-end. The application will require a back-end database to store user profiles, user transactions, and the list of music/book titles available at the site. The application will also have a middle tier (the web server plus scripts which are executed by the server), to process the application requests sent from the browser. The browser will send WAP (Wireless Access Protocol) requests to the WAP gateway, which in turn will forward the request to the middle tier using HTTP. The middle tier will get the data from the back-end database, do some processing on the data, and send the reply back to the WAP gateway, which in turn will send the data back to the client browser using the WAP protocol: Import ant A WAP gateway is software that acts as a bridge between a network that supports WAP protocol and Internet Protocol (IP) network. Alternatives for the Back-End Database The back-end database stores the following data: . Information about registered users . Book and music titles available at the site . Record of transactions carried out by users We have two alternatives for storing the above listed information: . Flat files . Relational databases like Oracle, MySQL, or Sybase Flat files are ruled out, because that would lead to implementing lots of functionality, like designing the layout so that the data can be manipulated later, and designing a simple interface for accessing the data from files. This functionality is already available in relational databases. We have chosen MySQL as our back-end database. The reasons for this include: . MySQL is an open source relational database, so it has a cost advantage over other commercial databases . MySQL is highly scalable and easy to administer . MySQL supports client APIs for a large set of programming languages (like Perl, C, and PHP), so it gives more choice of programming languages for implementing the middle tier Alternatives for the Middle Tier The middle tier will generate WML pages dynamically, using the data available in the back-end database. For example, to display the book titles available at the site, the middle tier will get the list of books from the back-end database, and will generate a WML page containing the list of books. The following are the alternatives for implementing the middle tier: . Common Gateway Interface (CGI) programs written in Perl/C. These programs can access the back-end database using the database’s language APIs. . Servlets, written in Java. Servlets can access the back-end database using Java’s SQL APIs and the database’s JDBC driver. JDBC drivers are available for almost all databases. . Server-side scripting language like PHP, JavaServer Pages (JSP), and Active Server Pages (ASP). These languages support APIs for accessing almost all relational databases. PHP is chosen for implementing the middle tier for the following reasons: . PHP is available on a large set of platforms (Linux, UNIX, and Windows NT) and a variety of web servers (Apache and IIS). Therefore, we get a choice of platform and web server for hosting the middle tier. . Performance is one of the implicit requirements for any web-based application, so Page 545
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