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Comp 105
SSU
Topic 9: Databases and Information Management
I.
Databases and Information Management
A. Data vs Information
1. Recall that a computer system processes data to produce information.
a. Data is a collection of pieces with no individual meaning.
b. Information is data that has been organized into useful groups that give
it meaning.
2. Fig. 13-1
B. Aspects of Data Management
1. Data Integrity
a. The degree of accuracy of data used by a computer system
b. Accurate information cannot be retrieved from inaccurate data
2. Data Security
a. The protection of data to prevent loss or misuse
C. The Data Hierarchy
1. Database
2. Files
3. Records
4. Fields
5. Characters
6. Fig. 13-2
D. Types of Data
1. Text
2. Numeric
3. Currency
4. Data
5. Memo
6. Hyperlink
E. Data Maintenance
1. Procedures used to keep data current
a. Adding Records
b. Changing Records
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c. Deleting Records
d. Data Validation
2. Changes are made to a copy of the data file called a transaction file. The
master file is updated only after the transaction file is validated.
F. Data Validation Procedures
1. Validation is the process of comparing data to a set of rules or values to
determine accuracy.
2. Types of validity checks
a. Alphabetic / Numeric Check - verifies data type
b. Completeness Check - verifies the presence of data
c. Range Check - verifies data has appropriate values
d. Consistency Check - verifies data relationships
e. Fig. 13-7
G. Primary Key
1. A primary key is a set of fields that differentiate the records in a data file.
2. Often the primary key is a single key field that is present solely for the purpose
of identifying records.
a. E.g. A customer account number.
3. The validity of a key field can be checked with the use of a check digit.
a. Acct. # 52347  5 + 2 +3 + 4 + 7 = 21  2 + 1 = 3
b. Acct. # with check digit becomes 523473
H. File Processing Approach
1. Each department in a organization keeps its own files
a. Example: Separate student files stored byRegistrar, Health Center,
Business Office and University Relations
2. Problems with this approach
a. Data Redundancy
b. Data Isolation
c. Fig. 13-9
I. Database Approach
1. Single centralized data storage of related files where different departments
have specific programs for accessing the data (Fig. 10-10)
2. Advantages
a. Reduced Data Redundancy
Comp 105
SSU
b. Improved Data Integrity
c. Shared Data
d. Reduced Development Time
e. Easier Reporting
II.
Database Management Systems
A. A database management system (DBMS) is a piece of software to control access to a
database.
B. A DBMS contains the following component features
1. Data dictionary
2. Data maintenance and retrieval
3. Data security
4. Backup and Recovery
C. Data Dictionary
1. A data dictionary stores stores information about each file in the database and
each field within those files.
2. The DBMS uses the data dictionary to perform validation checks and maintain
the integrity of data.
D. Data Maintenance and Retrieval
1. Data maintenance is the updating or adding of records as already discussed.
2. To retrieve data and organizing it into information the user forms a query
based on specific criteria.
a. E.g. List all students with GPA over 3.0.
3. A query language is used to formulate the query.
4. Query languages often use notation very similar to mathematical logic.
E. Data Security
1. A DBMS provides security by allowing the database administrator to assign
access privileges for a file.
2. The access privileges define what operations a particular user may perform on
the file.
a. A faculty may read a students file
b. Only the registrar may update the file
F. Backup and Recovery
1. Backup utilities can be included in the DBMS to allow for easy copying of
data files
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SSU
2. Some more sophisticated systems keep a transaction log of every operation
performed on the database file
a. The log can be used to reconstruct the database in case of damage
G. Data Models
1. There are many types of data models used
a. Relational
b. Object-oriented
c. Hierarchical
d. Network
e. Object-relational
2. Relational and object-relational are the most common and the most popular.
H. Relational Database Model
1. Data is stored in tables that consist of rows and columns similar to a
spreadsheet.
2. Each row represents a record and thus has a primary key.
3. Each column in a row represents a field of that row’s record.
4. Fig. 13-22
5. A popular query language for relational databases called Structured Query
Language (SQL) is based on relational algebra.
6. Fig. 13-26
I. Object-Oriented Database Model
1. Objects are program entities that model items in the problem domain.
a. E.g. Students, Courses, Faculty, Schedules, etc.
2. An object oriented database is built around these objects and their
relationships with each other.
3. An object-relational database combines the ideas of the relational model and
the object model.
III.
Information
A. The purpose of a DBMS is to manage data in a way that it can be organized and
retrieved as information.
B. Information is an organization’s most valuable asset.
C. Valuable information should be:
1. Accurate
2. Verifiable
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SSU
3. Timely
4. Organized
5. Meaningful
6. Cost effective
D. Using Information
1. Management requires information to make decisions
E. The use of information depends on the management level
F. Information Systems
1. An information system is a collection of hardware, software, data, people and
procedures designed to generate information.
2. We will study information systems and their development next time.