Database Reference
In-Depth Information
9
DATABASE MANAGEMENT
APPROACHES
CHAPTER
LEARNING OBJECTIVES
Describe distributed database management systems (DDBMSs)
Discuss client/server systems
Examine the ways databases are accessed on the Web
Discuss XML and related document specification standards
Define data warehouses and explain their structure and access
Discuss the general concepts of object-oriented DBMSs
INTRODUCTION
In previous chapters, you learned about relational DBMSs (RDBMSs), which dominate the database market today. In this
chapter, you will examine several database management topics, most of which are applicable to relational systems.
The centralized approach to processing data, in which users access a central computer through personal computers
(PCs) and workstations, dominated organizations from the late 1960s through the mid-1980s because there was no alterna-
tive approach to compete with it. The introduction of reasonably priced PCs during the 1980s, however, facilitated the
placement of computers at various locations within an organization; users could access a database directly at those loca-
tions. Networks connected these computers, so users could access not only data located on their local computers but also
data located anywhere along the entire network. In the next section, you will study the issues involved in distributed data-
bases where a database is stored on more than one computer.
Organizations often off-load, or shift, data communications functions from central computers to smaller computers to
improve processing speed. Similarly, organizations often use client/server systems to off-load database access functions
from central computers to other computers; you'll study these client/server systems. You will also learn about accessing
databases on the Web and the growing importance of XML and related document standard specifications. Next you'll learn
about special database systems, called data warehouses, that allow you to retrieve data rapidly. Finally, you will study
object-oriented systems, which treat data as objects and include the actions that operate on the objects.
DISTRIBUTED DATABASES
Premiere Products has multiple locations nationwide. Each location has its own sales reps and customer base,
and each location maintains its own inventory. Instead of using a single centralized computer accessed by all
the separate locations, Premiere Products is considering installing a computer at each site. If it does so, each
site would maintain its own data about its sales reps, customers, parts, and orders. Occasionally, an order at
one site might involve parts from another site. In addition, a customer serviced at one site might place orders
for its subsidiaries that are located closer to other sites. Consequently, the computer at a particular site
would need to communicate with the computers at all the other sites. The computers would have to be con-
nected in a communications network,ornetwork, as illustrated in Figure 9-1.
