Information Technology Reference
In-Depth Information
SUMMARY
Principle
Data management and modeling are key aspects of
organizing data and information.
A DBMS is a group of programs used as an interface between
a database and its users and other application programs.
When an application program requests data from the
database, it follows a logical access path. The actual retrieval
of the data follows a physical access path. Records can be
considered in the same way: A logical record is what the
record contains; a physical record is where the record is
stored on storage devices. Schemas are used to describe the
entire database, its record types, and their relationships to
the DBMS.
A DBMS provides four basic functions: providing user
views, creating and modifying the database, storing and
retrieving data, and manipulating data and generating
reports. Schemas are entered into the computer via a data
definition language, which describes the data and relation-
ships in a specific database. Another tool used in database
management is the data dictionary, which contains detailed
descriptions of all data in the database.
After a DBMS has been installed, the database can be
accessed, modified, and queried via a data manipulation lan-
guage. A more specialized data manipulation language is the
query language, the most common being Structured Query
Language (SQL). SQL is used in several popular database
packages today and can be installed on PCs and mainframes.
Popular single-user DBMSs include Corel Paradox
and Microsoft Access. IBM, Oracle, and Microsoft are the
leading DBMS vendors. Database as a Service (DaaS), or
Database 2.0, is a new form of database service in which
clients lease use of a database on a service provider's site.
Selecting a DBMS begins by analyzing the information
needs of the organization. Important characteristics of
databases include the size of the database, the number of
concurrent users, its performance, the ability of the DBMS to
be integrated with other systems, the features of the DBMS,
the vendor considerations, and the cost of the database man-
agement system.
Data is one of the most valuable resources that a firm pos-
sesses. It is organized into a hierarchy that builds from the
smallest element to the largest. The smallest element is the
bit, a binary digit. A byte (a character such as a letter or
numeric digit) is made up of eight bits. A group of characters,
such as a name or number, is called a field (an object). A col-
lection of related fields is a record; a collection of related
records is called a file. The database, at the top of the hier-
archy, is an integrated collection of records and files.
An entity is a generalized class of objects for which data
is collected, stored, and maintained. An attribute is a char-
acteristic of an entity. Specific values of attributes—called
data items—can be found in the fields of the record describing
an entity. A data key is a field within a record that is used to
identify the record. A primary key uniquely identifies a record,
while a secondary key is a field in a record that does not
uniquely identify the record.
Traditional file-oriented applications are often character-
ized by program-data dependence, meaning that they have
data organized in a manner that cannot be read by other pro-
grams. To address problems of traditional file-based data
management, the database approach was developed. Bene-
fits of this approach include reduced data redundancy,
improved data consistency and integrity, easier modification
and updating, data and program independence, standardiza-
tion of data access, and more-efficient program development.
One of the tools that database designers use to show the
relationships among data is a data model. A data model is a
map or diagram of entities and their relationships. Enterprise
data modeling involves analyzing the data and information
needs of an entire organization. Entity-relationship (ER) dia-
grams can be employed to show the relationships between
entities in the organization.
The relational model places data in two-dimensional
tables. Tables can be linked by common data elements, which
are used to access data when the database is queried. Each
row represents a record. Columns of the tables are called
attributes, and allowable values for these attributes are called
the domain. Basic data manipulations include selecting, pro-
jecting, and joining. The relational model is easier to control,
more flexible, and more intuitive than the other models
because it organizes data in tables.
Principle
The number and types of database applications will
continue to evolve and yield real business benefits.
Traditional online transaction processing (OLTP) systems put
data into databases very quickly, reliably, and efficiently, but
they do not support the types of data analysis that today's
businesses and organizations require. To address this need,
organizations are building data warehouses, which are rela-
tional database management systems specifically designed
to support management decision making. Data marts are
subdivisions of data warehouses, which are commonly
devoted to specific purposes or functional business areas.
Principle
A well-designed and well-managed database is an
extremely valuable tool in supporting decision
making.
