Informatics 2A
Chapter 10: Database Development Process
Topics covered in this chapter:
• The role of databases Information Systems
• The Systems Development Life Cycle (SDLC) for successful implementation of
Information Systems
• The Database Life Cycle (DBLC) for successful implementation of databases
• How to conduct evaluation and revision within the SDLC and DBLC frameworks
• Database design strategies
• Common threats to the security of the data
• The importance of the database administration
• The roles of the database administrator (DBA)
2
The Information System
The Information System
• Provides for data collection, storage, and retrieval
• Composed of people, hardware, software, database(s), application programs,
and procedures
• Systems analysis
• Process that establishes need for and extent of information system
• Systems development
• Process of creating information system
4
The Information System (Continued)
5
The Information System (Continued)
• Information system performance depends on triad of factors:
• Database design and implementation
• Application design and implementation
• Administrative procedures
• Database development
• Process of database design and implementation
• Primary objective is to create complete, normalized, non-redundant (to the
extent possible), and fully integrated, conceptual, logical, and physical
database models
6
The Systems Development Life Cycle (SDLC)
The Systems Development Life Cycle (SDLC)
• Traces history (life cycle) of information system
• Provides “big picture” within which database design and application
development can be mapped out and evaluated
• Divided into following five phases:
• Planning
• Analysis
• Detailed systems design
• Implementation
• Maintenance
• Iterative rather than sequential process
9
The Systems Development Life Cycle (SDLC)
10
Planning
• Initial assessment made of information-flow-and-extent requirements
• Must begin to study and evaluate alternate solutions
• Technical aspects of hardware and software requirements
• System cost
11
Analysis
• Problems defined during planning phase are examined in greater detail during
analysis
• Thorough audit of user requirements
• Existing hardware and software systems are studied
• Goal is better understanding of system’s functional areas, actual and potential
problems, and opportunities
• Includes creation of logical system design
• Must specify appropriate conceptual data model, inputs, processes, and
expected output requirements
• Yields functional descriptions of system’s components (modules) for each
process within database environment
12
Detailed Systems Design
•
•
•
•
Designer completes design of system’s processes
Includes all necessary technical specifications
Steps are laid out for conversion from old to new system
Training principles and methodologies are also planned
13
Implementation
• Hardware, DBMS software, and application programs are installed, and
database design is implemented
• Cycle of coding, testing, and debugging continues until database is ready to
be delivered
• Database is created and system is customized by creation of tables and views,
and user authorizations
14
Maintenance
•
•
Maintenance activities group into three types:
• Corrective maintenance in response to systems errors
• Adaptive maintenance due to changes in business environment
• Perfective maintenance to enhance system
Computer-assisted systems engineering
• Make it possible to produce better systems within reasonable amount of
time and at reasonable cost
15
The Database Life Cycle (DBLC)
The Database Life Cycle (DBLC)
18
The Database Initial Study
• Overall purpose:
• Analyze company situation
• Define problems and constraints
• Define objectives
• Define scope and boundaries
• Interactive and iterative processes required to complete first phase of DBLC
successfully
19
The Database Initial Study (Cont.)
20
The Database Initial Study – Analyze the Company Situation
Analysis
• To break up any whole into its parts so as to find out their nature, function,
and so on
• Company situation
• General conditions in which company operates, its organizational structure,
and its mission
• Analyze company situation
• Discover what company’s operational components are, how they function,
and how they interact
•
21
The Database Initial Study – Define Problems and Constraints
•
•
•
•
Managerial view of company’s operation is often different from that of end
users
Designer must continue to carefully probe to generate additional information
that will help define problems within larger framework of company operations
Finding precise answers is important
Defining problems does not always lead to perfect solution
22
The Database Initial Study – Define Objectives
•
•
Designer must ensure that database system objectives correspond to those
envisioned by end user(s)
Designer must begin to address following questions:
• What is proposed system’s initial objective?
• Will system interface with other existing or future systems in the company?
• Will system share data with other systems or users?
23
The Database Initial Study – Define Scope and Boundaries
•
•
Scope
• Defines extent of design according to operational requirements
• Helps define required data structures, type and number of entities, and
physical size of database
Boundaries
• Limits external to system
• Often imposed by existing hardware and software
24
Database Design
25
Database Design (Continued)
26
Database Design (Continued)
• Loosely related to analysis and design of larger system
• Systems analysts or systems programmers are in charge of designing other
system components
• Their activities create procedures that will help transform data within database
into useful information
• Does not constitute sequential process
• Iterative process that provides continuous feedback designed to trace
previous steps
27
Database Design (Continued)
28
I. Conceptual Design Overview
• Data modeling used to create an abstract database structure that represents
real-world objects in most realistic way possible
• Must embody clear understanding of business and its functional areas
• Ensure that all data needed are in model, and that all data in model are needed
29
I. Conceptual Design Overview (Continued)
• Requires four steps
• Data analysis and requirements
• Entity relationship modeling and normalization
• Data model verification
• Distributed database design
30
II. DBMS Software Selection
• Critical to information system’s smooth operation
• Advantages and disadvantages should be carefully studied
• Some factors affecting purchasing of DBMS:
• Cost
• DBMS features and tools
• Underlying model
• Portability
• DBMS hardware requirements
31
III. Logical Design
• Used to translate conceptual design into internal model for selected
database management system
• Phases of the logical design stage phases:
1. Creating the logical data model.
2. Validating the logical data model using normalization.
3. Assigning and validating integrity constraints.
4. Merging logical models constructed for different parts of the database
together.
5. Reviewing the logical data model with the user.
32
IV. Physical Design
• Process of selecting data storage and data access characteristics of database
• Physical database design stages:
1. Analyze data volume and database usage.
2. Translate each relation identified in the logical data model into tables.
3. Determine a suitable file organization.
4. Define indexes.
5. Define user views.
6. Estimate data storage requirements.
7. Determine database security for users.
33
End of Part 1
Informatics 2A
Chapter 10: Database Development Process – Part 2
Implementation and Loading
36
Implementation and Loading (Continued)
• Performance is one of most important factors in certain database
implementations
• Not all DBMSs have performance-monitoring and fine-tuning tools
embedded in their software
• There is no main or standard measurement for database performance
• Database can be subject to data loss through unintended data deletion and
power outages
• Data backup and recovery procedures create safety valve that allow database
administrator to ensure availability of consistent data
• Integrity of database is enforced through proper
use of primary and
foreign key rules
37
Database Security
• Data must be protected from access by unauthorized users
• Establish security goals
• What are we trying to protect the database from?
• What security related problems are we trying to prevent?
• The most common security goals relate to the integrity, confidentiality and
the availability of data.
38
Threats to Security
• Threats are any set of circumstances that have the potential to cause loss,
misuse or harm to the system and/or its data.
• Examples:
• Unauthorized access and modification of data.
• Human error which causes accidental loss of data.
• Electronic infections such as viruses, worms and Trojan Horses.
• Poor database administration.
• The occurrence of natural disasters such as hurricanes, fires or floods.
40
Threats to Security (Continued)
Threats can cause:
• Loss of integrity of data through unauthorized modification
• Example: A person gaining unauthorized access to a bank account and
removing some money from the account.
• Loss of availability of the data
• Example: Some adversary causes the database system from being
operational which stops authorized users of the data from accessing it.
• Loss of confidentiality of the data (privacy of data).
• Example: A person gaining access to private information such as a
password or a bank
account balance.
41
Threats to Security – Examples
42
Data Security Measures
• Physical security allows only authorized personnel physical access to specific
areas.
• User authentication is a way of identifying the user and verifying that the user is
allowed to access some restricted data or application.
• achieved through the use of passwords and access rights.
• Audit trails are usually provided by the DBMS to check for access violations.
43
Data Security Measures (Continued)
•
•
•
•
•
Data encryption
User-defined policies and procedures
Backup and recovery strategies
Antivirus software
Firewalls
44
Testing and Evaluation
45
Operation
46
Maintenance and evolution
47
Parallel Activities in the DBLC and the SDLC
48
Database Design Strategies
Database Design Strategies
• Two classical approaches to database design:
• Top-down design
• Identifies data sets
• Defines data elements for each of those sets
• Bottom-up design
• Identifies data elements (items)
• Groups them together in data sets
50
Database Design Strategies Top-down vs. bottom-up design
sequencing
51
Centralized vs Decentralized Design
Centralized vs. Decentralized Design
•
Database design may be based on two very different design philosophies:
• Centralized design
• Productive when data component is composed of relatively small
number of objects and procedures
• Decentralized design
• Used when data component of system has considerable number of
entities and complex relations on which very complex operations are
performed
53
Centralized Design
54
Decentralized Design
55
Centralized vs. Decentralized Design (Continued)
• Aggregation process
• Requires designer to create single model in which various aggregation
problems must be addressed:
• Synonyms and homonyms
• Entity and entity subtypes
• Conflicting object definitions
56
Centralized vs. Decentralized Design Summary of aggregation
problems
57
Database Administration
Database Administration
• Data management is a complex job
• Led to the development of the database administration function
• The person responsible for the control of the centralized and shared database
is the database administrator (DBA).
59
The placement of the DBA function
60
DBA Activities
• Database planning, including the definition of standards, procedures and
enforcement.
• Database requirements gathering and conceptual design.
• Database logical design and transaction design.
• Database physical design and implementation.
• Database testing and debugging.
• Database operations and maintenance, including installation, conversion and
migration.
• Database training and support.
61
The DBA in the Organisation
62
DBA Skills
63
The Managerial Role of the DBA
64
The Technical Role of the DBA
•
•
•
•
•
•
Evaluating, selecting and installing the DBMS and related utilities.
Designing and implementing databases and applications.
Testing and evaluating databases and applications.
Operating the DBMS, utilities and applications.
Training and supporting users.
Maintaining the DBMS, utilities and applications.
65
Developing a Data Administration Strategy
• Critical step for any organization is to ensure its information system supports
strategic plans for each of the company’s business areas
• Database administration strategy must not conflict with information systems
plans
• Information engineering
• Translates company’s strategic goals into data and applications that will
help company achieve those goals
• Output of IE process is information systems architecture that serves as
basis for planning, development, and control of future information systems
66
Forces affecting the development of the ISA
67
End of Part 2