Verdict: System Architecture and Operation

System architecture

Verdict is built around a three-tier architecture model, which comprises the following:

  1. The client tier
  2. The middle tier
  3. The database tier

At the top level of the model is the client tier, which includes the Web browser software that interacts with the
Verdict application. In between the top and bottom tiers is the middle tier, which communicates data to and from the client and database tiers.

The middle tier is more complex and contains most of the application logic. The Web server, the scripting engine and the scripts reside in this tier. The base tier of the Verdict application is the datsbase tier, which is made up of a database management system (DBMS) that manages the data that is created, added, modified, deleted and/or requested by the end-userA.
VERDICT has been developed using PHP as the scripting language. PHP is an open source, server-side, HTML embedded scripting language used to create dynamic Web pages. It is compatible with many types of databases. The front-end of the VERDICT prototype is designed using Macromedia Dreamweaver and Fireworks (for graphics).

Three-tier architecture of verdict

Figure 4.4 Three-tier architecture of verdict

The application mainly consists of a series of Web-based questionnaire forms that can be accessed by the end-user/s using standard Web browsers such as MS Internet Explorer and Netscape. Any information that is added to these forms (i.e. end-user responses) is stored in the MySQL database. MySQL is an open source RDBMS2 (relational
database management system) that can run on UNIX, Windows and Mac operating systems. It has become a popular alternative to proprietary database systems because of its economy, speed and reliability. The VERDICT system resides on a server with which the end-user communicates. This forms the core of the middle tier.

Operation

Any requests made by the end-users are communicated via the Web server. This action invokes the PHP script code embedded in the Web page to request and retrieve the data from the MySQL database. This data, returned by the MySQL database, is then processed by the PHP script. The processed data is then presented to the end-user on a Web page. A high level view of this process, which includes the operations and the system architecture of the VERDICT application are illustrated in below photo

Operations of VERDICT

Figure 4.5
Operations of VERDICT

End-user companies only require a computer and an Internet connection to access and operate the tool. The performance of the tool will depend on the speed of the Internet connection and the version-type of the operating systems. For example, end-user companies with broadband connections will be able to access the site and process information faster than those with dial-up connections.

End-users can access VERDICT online using the Web-address:  http://civil-unrest.lboro.ac.uk/cvkr
The next section describes the actual working of the VERDICT software using an end-user case study.

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