Chapter 1 Notes for Module 1

What is a computer file system, and what are its problems?

A computer file system stores data in independent, unrelated files on disk. The sharing, security and integrity of the data can’t be enforced efficiently because of data dependence and data redundancy problems.

What are the DBMS functions, and why are they important?

A proper database system eliminates data dependence and improves data integrity by minimizing data redundancy. Please note that good database design is the key to reaping the rewards of a proper database system. The best programmers and applications developers cannot rescue a database system from the effects of poor database design.

Describe the database environment and the different types of database systems.

The DBMS is an important component of the database environment, but this environment also includes different types of hardware and software, people who perform different functions within the environment, procedures designed to accomplish desired activities, and data. The data constitute the database’s central component through which information is generated. The main purpose of the database environment is to help an organization perform its mission and achieve its goals. Review Figure 1.7 in the text.

Note that the database administrator writes and enforces the procedures and standards that are then used by designers, analysts, programmers, and end users. The end users use the application programs created by analysts and programmers. Analysts wear two hats. They are end users in that they perform analysis based on the application programs. They also help produce application programs by collaborating with programmers to define the parameters of the applications. In turn, the application programs make use of the DBMS, which manages the data. Note also that the database designer and the database administrator perform their jobs through the interface. The interface is the gateway to the database, which resides within the hardware. Finally, the System Administrator manages the entire system.

What is a Database Model?

A database model is a collection of logical constructs used to represent the database’s data structure as well as the data relationship(s) found within that structure. Types of conceptual database models include: E-R, Object Oriented, and semantic. Implementation database models include: hierarchical, network, and relational. These models represent data relationships: 1:1, 1:M, and M:N.

Why is database design so important?

Modern database-and-applications development software is so easy to use that many people can quickly learn to implement a simple database and develop simple applications within a week or so, without giving design a thought. As data and reporting requirements become more complex, those same people will simply produce the required add-ons. That’s how data redundancies and all their attendant anomalies develop, thus reducing the “database” and its applications to a status worse than useless. Remember: good applications can’t overcome bad database designs. The existence of a DBMS does not guarantee good data management, nor does it ensure that the database will be able to generate correct and timely information. Ultimately, the end user and the designer decide what data will be stored in the database. Most current DBMSs are based on the relational model. The relational model is conceptually simpler than the hierarchical and network models. Database design is a process that, in effect, yields a detailed database blueprint. This blueprint, usually in the form of an E-R diagram or ERD, is used as the basis for database implementation.