Mogadisho_ICT

1-7c Managing the Database System: A Shift in Focus
The introduction of a database system over the file system provides a framework in
which strict procedures and standards can be enforced. Consequently, the role of the
human component changes from an emphasis on programming (in the file system) to a
focus on the broader aspects of managing the organization’s data resources and on the
administration of the complex database software itself.
The database system makes it possible to tackle far more sophisticated uses of the data
resources, as long as the database is designed to make use of that power. The kinds of data
structures created within the database and the extent of the relationships among them
play a powerful role in determining the effectiveness of the database system.
Although the database system yields considerable advantages over previous data
management approaches, database systems do carry significant disadvantages:
• Increased costs. Database systems require sophisticated hardware and software and
highly skilled personnel. The cost of maintaining the hardware, software, and personnel required to operate and manage a database system can be substantial. Training,
licensing, and regulation compliance costs are often overlooked when database systems are implemented.
• Management complexity. Database systems interface with many different technologies and have a significant impact on a company’s resources and culture. The changes
introduced by the adoption of a database system must be properly managed to ensure
that they help advance the company’s objectives. Because database systems hold crucial company data that are accessed from multiple sources, security issues must be
assessed constantly.
• Maintaining currency. To maximize the efficiency of the database system, you must keep
your system current. Therefore, you must perform frequent updates and apply the latest
patches and security measures to all components. Because database technology advances
rapidly, personnel training costs tend to be significant.
• Vendor dependence. Given the heavy investment in technology and personnel training, companies might be reluctant to change database vendors. As a consequence,
vendors are less likely to offer pricing point advantages to existing customers, and
those customers might be limited in their choice of database system components.
• Frequent upgrade/replacement cycles. DBMS vendors frequently upgrade their products by adding new functionality. Such new features often come bundled in new
upgrade versions of the software. Some of these versions require hardware upgrades.
Not only do the upgrades themselves cost money, it also costs money to train database
users and administrators to properly use and manage the new features.
Now that you know what a database and DBMS are, and why they are necessary, you are
ready to begin developing your career as a database professional

1-8 Preparing for Your Database
Professional Career
In this chapter, you were introduced to the concepts of data, information, databases, and
DBMSs. You also learned that, regardless of what type of database you use (OLTP, OLAP,
or NoSQL), or what type of database environment you are working in (e.g., Oracle,
Microsoft, IBM, or Hadoop), the success of a database system greatly depends on how
well the database structure is designed

Translating Business
Rules into Data Model
Components
Business rules set the stage for the
proper identifcation of entities,
attributes, relationships, and constraints.
In the real world, names are used to
identify objects. If the business
environment wants to keep track of the
objects, there will be specifc business
rules for the objects. As a general rule, a
noun in a business rule will translate into
an entity in the model, and a verb (active
or passive) that associates the nouns will
translate into a relationship among the
entities. For example, the business rule “a
customer may generate many invoices”
contains two nouns (customer and
invoices) and a verb (generate) that
associates the nouns. From this business
rule, you could deduce the following:
• Customer and invoice are objects of
interest for the environment and should be
repre-�
sented by their respective entities.• Tere
is a generate relationship between
customer and invoice.
To properly identify the type of
relationship, you should consider that
relationships are bidirectional; that is,
they go both ways. For example, the
business rule “a customer may generate
many invoices” is complemented by the
business rule “an invoice is generated by
only one customer.” In that case, the
relationship is one-to-many (1:M).
Customer is the “1” side, and invoice is
the “many” side.
As a general rule, to properly identify �
the relationship type, you should ask
two questions:
• How many instances of B are related to
one instance of A?• How many instances
of A are related to one instance of B?
For example, you can assess the
relationship between student and class by
asking two questions:
• In how many classes can one student
enroll? Answer: many classes.• How many
students can enroll in one class? Answer: �

Part 1Database Conceptssame job
yield very diferent perceptions of what
the job components are. While such a
discovery may point to “management
problems,” that general diagnosis does
not help the database designer. Te
database designer’s job is to reconcile
such diferences and verify the results of
the reconciliation to ensure that the
business rules are appropriate and
accurate.
Te process of identifying and
documenting business rules is essential
to database design for several reasons:
• It helps to standardize the company’s
view of data.
• It can be a communication tool between
users and designers.
• It allows the designer to understand the
nature, role, and scope of the data.• It
allows the designer to understand business
processes.
• It allows the designer to develop
appropriate relationship participation
rules and
constraints and to create an accurate data
model.�
Of course, not all business rules can be
modeled. For example, a business rule
that specifes “no pilot can fy more than
10 hours within any 24-hour period”
cannot be modeled in the database
model directly. However, such a business
rule can be represented and enforced by
application sofware.�

Discovering Business
Rules
Te main sources of business rules are
company managers, policy makers,
department managers, and written
documentation such as a company’s
procedures, standards, and operations
manuals. A faster and more direct source
of business rules is direct interviews with
end users. Unfortunately, because
perceptions difer, end users are
sometimes a less reliable source when it
comes to specifying business rules. For
example, a maintenance department
mechanic might believe that any
mechanic can initiate a maintenance
procedure, when actually only mechanics
with inspection authorization can
perform such a task. Such a distinction
might seem trivial, but it can have major
legal consequences. Although end users
are crucial contributors to the
development of business rules, it pays to
verify end-user perceptions. Too ofen,
interviews with several people who
perform the
business rule�
A description of a policy, procedure, or principle
within an organization. For example, a pilot cannot
be on duty for more than 10 hours during a 24-hour
period, or a professor may teach up to four classes
during �

Database System: �

Business Rules
When database designers go about
selecting or determining the entities,
attributes, and relationships that will be
used to build a data model, they might
start by gaining a thorough
understanding of what types of data exist
in an organization, how the data is used,
and in what time frames it is used. But
such data and information do not, by
themselves, yield the required
understanding of the total business.
From a database point of view, the
collection of data becomes meaningful
only when it refects properly defned
business rules. A business rule is a brief,
precise, and unambiguous description of
a policy, procedure, or principle within a
specifc organization. In a sense, business
rules are misnamed: they apply to any
organization, large or small—a business,
a government unit, a religious group, or a
research laboratory—that stores and uses
data to generate information.
Business rules derived from a detailed
description of an organization’s
operations help to create and enforce �
actions within that organization’s
environment. Business rules must be
rendered in writing and updated to
refect any change in the organization’s
operational environment.�
Properly written business rules are used
to defne entities, attributes, relationships,
and constraints. Any time you see
relationship statements such as “an agent
can serve many customers, and each
customer can be served by only one agent,”
business rules are at work. You will see the
application of business rules throughout
this book, especially in the chapters
devoted to data modeling and database � To be efective, business rules must be
easy to understand and widely
disseminated to ensure that every person
in the organization shares a common
interpretation of the rules. Business rules
describe, in simple language, the main
and distinguishing characteristics of the
data as viewed by the company. Examples
of business rules are as follows:• A
customer may generate many invoices.•
An invoice is generated by only one
customer.• A training session cannot be
scheduled for fewer than 10 employees or
for more than
30 employees.�
Note that those business rules establish
entities, relationships, and constraints.
For example, the frst two business rules
establish two entities (CUSTOMER and
INVOICE) and a 1:M relationship
between those two entities. Te third
business rule establishes a constraint (no
fewer than 10 people

https://www.vidrise.com/v/80qpd/

Microsoft Excel 2023: Casharka 7 Aad Barro Sida Loo Isticmaalo excel | Number format | print ❲ ▹ ❳ MogadishoICT Channel