1.5 The Database Approach

An information system that uses a database management system (DBMS) to manage its information has a particular structure, comprising three components: DBMS, data, and application software. This structure as described below is referred to as the database approach to information system development.

The central component of the database approach is the DBMS. This software is also referred to as the database engine or the back end. With regard to the data it manages, it has several responsibilities, including the following:

  • Data Definition: providing a way to define and build the database

  • Data Manipulation: providing a way to insert and update data in the database

  • Query Execution: answering questions about the data in the database

  • Data Integrity: ensuring that data stored is well formed

  • Data Security: enforcing restrictions about who is able to access what data

  • Data Portability: providing a means for backup and restore

  • Data Recovery: protecting data from loss in the case of a catastrophic failure in hardware of software

  • Provenance: logging capabilities to provide an audit trail for data changes

  • Performance: providing a means to tune and optimize operation

  • Multiuser Concurrency: supporting the activities of many users at the same time

  • Automatic Processing: providing a way to define rules to execute business logic (e.g. stored procedures and triggers)

As can be seen from the above list, a DBMS is a complex software application. While all database management systems may not provide all of these features listed, these features are the general characteristics of today’s DBMSs. Using a database requires considerable expertise and knowledge about the specific DBMS being used. Some of the more popular DBMS's today are MySQL, Microsoft SQL Server, Oracle, PostgreSQL, Microsoft Access, and IBM's DB2.

The second component in the database approach is the data. Although the physical location or manner in which the data are stored may be important for performance reasons, the location of the data does not determine whether or not a system is developed using the database approach. As long as the DBMS has access and is able to perform its responsibilities with respect to the data, the details of the data storage are not relevant. The data could be stored on a single local hard disk, an array of disks on a single computing device, the disks of multiple devices, or in any other configuration.

The final component of the database approach is the application, also called front end software. Application software interacts with the DBMS to provide information to a user. It may also provide a way for a user to invoke other functionalities of the DBMS. In fact, the DBMS software itself is non-visual, meaning that the user does not interact directly with the DBMS. Any software that provides an interface for the user to invoke procedures in the DBMS is defined as application software. Application software may provide complex functionality to database administrators or display the results of a fixed information request. Any program that sends a request to the DBMS and receives a response is application software.

Once the application has determined what the user is trying to accomplish, it sends a request to the DBMS. The request may be an instruction to change data or a request for information such as the list of employees who were hired on a particular date. All relational databases use a standard language to receive and process requests. The standard language is called Structured Query Language.

The DBMS receives the request and determines if the operation requested is allowed for the authenticated user. If the operation is allowed, the DBMS completes the operation and sends a response to the application. The application then communicates the information to the user. If the operation is not authorized for the user or if there is an error in fulfilling the operation, the DBMS responds with an appropriate message. Again, it is up to the application to display that to the user. It is a critical feature of the database approach that the application never bypasses the DBMS to access stored data directly.

Figure 1.2 illustrates some of the primary components of a typical DBMS and how they are used in an information system.

Figure 1.2: The Database Approach
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