Database Design: The Paradigm Shift
Until now, we have taken it for granted that there is a structure to the data in the database.
For example, we have identified four tables in Figure 1.7: PropertyForRent, PrivateOwner,
Client, and Lease. But how did we get this structure? The answer is quite simple: the
structure of the database is determined during database design. However, carrying out
database design can be extremely complex. To produce a system that will satisfy the
organization’s information needs requires a different approach from that of file-based systems,
where the work was driven by the application needs of individual departments. For
the database approach to succeed, the organization now has to think of the data first and
the application second. This change in approach is sometimes referred to as a paradigm
shift. For the system to be acceptable to the end-users, the database design activity is
crucial. A poorly designed database will generate errors that may lead to bad decisions
being made, which may have serious repercussions for the organization. On the other
hand, a well-designed database produces a system that provides the correct information
for the decision-making process to succeed in an efficient way.
The objective of this book is to help effect this paradigm shift. We devote several
chapters to the presentation of a complete methodology for database design (see Chapters
15–18). It is presented as a series of simple-to-follow steps, with guidelines provided
throughout. For example, in the Entity–Relationship diagram of Figure 1.6, we have
identified six entities, seven relationships, and six attributes. We provide guidelines to help
identify the entities, attributes, and relationships that have to be represented in the database.
Unfortunately, database design methodologies are not very popular. Many organizations
and individual designers rely very little on methodologies for conducting the design
of databases, and this is commonly considered a major cause of failure in the development
of database systems. Owing to the lack of structured approaches to database design,
the time or resources required for a database project are typically underestimated, the
databases developed are inadequate or inefficient in meeting the demands of applications,
documentation is limited, and maintenance is difficult.
Until now, we have taken it for granted that there is a structure to the data in the database.
For example, we have identified four tables in Figure 1.7: PropertyForRent, PrivateOwner,
Client, and Lease. But how did we get this structure? The answer is quite simple: the
structure of the database is determined during database design. However, carrying out
database design can be extremely complex. To produce a system that will satisfy the
organization’s information needs requires a different approach from that of file-based systems,
where the work was driven by the application needs of individual departments. For
the database approach to succeed, the organization now has to think of the data first and
the application second. This change in approach is sometimes referred to as a paradigm
shift. For the system to be acceptable to the end-users, the database design activity is
crucial. A poorly designed database will generate errors that may lead to bad decisions
being made, which may have serious repercussions for the organization. On the other
hand, a well-designed database produces a system that provides the correct information
for the decision-making process to succeed in an efficient way.
The objective of this book is to help effect this paradigm shift. We devote several
chapters to the presentation of a complete methodology for database design (see Chapters
15–18). It is presented as a series of simple-to-follow steps, with guidelines provided
throughout. For example, in the Entity–Relationship diagram of Figure 1.6, we have
identified six entities, seven relationships, and six attributes. We provide guidelines to help
identify the entities, attributes, and relationships that have to be represented in the database.
Unfortunately, database design methodologies are not very popular. Many organizations
and individual designers rely very little on methodologies for conducting the design
of databases, and this is commonly considered a major cause of failure in the development
of database systems. Owing to the lack of structured approaches to database design,
the time or resources required for a database project are typically underestimated, the
databases developed are inadequate or inefficient in meeting the demands of applications,
documentation is limited, and maintenance is difficult.
No comments: