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Chapter 10: Database Development process (545)
Systems analysis is used to determine the need for an information system and to establish its limits
10.1 The Information System (550)
Database: a carefully designed and constructed repository of facts
- the fact repository is a part of a larger whole AKA: Information System
Information systems provide for data collection, storage and retrieval.
- IS also facilitates the transformation of data into information and the management of data and information
- a complete IS comprises of people, hardware, software, application programs, procedures and the Database
Information System: An information system is designed to facilitate the transformation of data into information and to
manage both data and information. Thus, the database is a very important part of the information
system. Systems analysis is the process that establishes the need for, and the extent of, an
information system. Systems development is the process of creating an information system.
Systems analysis: the process that establishes the need for and scope of an IS.
System Development: the process of creating an IS.
Applications transform data into the information that forms the basis of decision making.
- applications produce formal reports, tabulations and graphic displays designed to produce insight
Figure 10-1: Generating information for decision-making
Data and code (in programs) work together to represent real-world business functions and activites
Performance of an information system depends on the triad of factors: (551)
- Database design and implementation
- Application design and implementations
- Administrative procedures
Database development: the process of database design and implementation
- primary objective: create complete, normalised, non-redundant and fully integrated conceptual, logical and physical database models.
- implementation phase includes creating the database storage structure , loading the data into the database and providing for data management
10.2 Systems Development Life Cycle (SDLC) (552):
- it traces the history / life cycle of an information system
Figure 10-2: Systems Development Life Cycle
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5 Phases of SDLC:
1. Planning
2. Analysis
3. Detailed Systems Design
4. Implementation
5. Maintenance
The SDLC is an iterative (not sequential) process.
10.2.1 Planning: (552)
This phase yields a general overview of the company and its objectives
Initial Assessment: An initial assessment of the information-flow-and-extent requirements must be made during the discovery portion of the SDLC
answers provided for the following questions:
should the existing system be continued? (not broken, don't fix it)
should the existing system be modified?
should the existing system be replaced?
Feasability Study: If a system must be replaced, themust be addressed
technical aspects of hardware and software requirements
system cost (million $ solution to a $1000 problem does not make sense)
operational cost (does the company have the human, technical and financial resources to keep the system operational?)
10.2.2 Analysis: (553)
The problems defined in the planning phase are examined in greater detail in this phase
A macro-analysis must be made of both indicidual and organizational needs, addressing the following questions:
- what are the requirements of the current system's end users?
- do those requirements fit into the overall information requirements?
This phase is an audit of user requirements
The result of this phase should be a better understanding of the system's functional areas, potential problems and opprtunities
End users and the system designer must work together to identify processes and uncover potential problem areas
This phase also includes the creation of a logical systems design - this design must specify the appropriate conceptual data model, input, processes and
expected output requirements
- DFD (data flow diagrams), HIPO (hierarchical input process output) diagrams and ER (entity relationship) diagrams are used when creating the
logical design
- database design's data modeling activities take place at this point to discover and describe all entities, their attributes and their relationships in the
database
Defining the logical system yields functional descriptions of a system's components (modules) for each process within the DB environment
All data transformations (processes) are described and documented using such systems analysis tools as DFD's.
The conceptual data model is validated against those processes
10.2.3 Detailed Systems Design: (554)
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The designer completes the design of system's processes
This design includes all necessary technical specifications for the screens, menus, reports and other devices that may be used to help make the system a
more effecient info generator
10.2.4 Implementation: (554)
During this phase, the hardware, DBMS software and application programs are installed and the database design is implemented
During the initial stages of implementation, the system enters into a cycle of coding, testing and debugging until it is ready to be delivered
The actual DB is created and the system is customized by the creation of tables and views, user authorisation etc
The DB contents may be loaded interactively or in batch modes, using the following methods and devices:
- customised user programs
- database interface programs
- conversion programs that import the data from a different file structure, using batch programs, a database utility or both
The system is subjected to exhaustive testing until it is ready for use.
After testing, the final documentation is reviewed and printed, and end users are trained
THE SYSTEM IS IN FULL OPERATION AFTER THIS PHASE but will still be continuously evaluated and fine-tuned
10.2.5 Maintenance: (554)
Three types of maintenance activities:
- corrective maintenance in response to system errors
- adaptive maintenance due to changesin the business environment
- perfective maintenance to enhance the system
Each system has a predetermined operational life span and it depends on its percieved utility
Reasons for reduced lifespan:
- rapid technological change
- cost of system maintenance
10.3 The Database Life Cycle (DBLC): (555)
Figure 10-3 Database Life Cycle (DBLC) - 556
6 Phases of the Database Life Cycle:
1. Database initial study
2. Database Design
3. Implementation and Loading
4. Testing and Evaluation
5. Operation
6. Maintenance and Evolution
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10.3.1 Database Initial Study:(555)
DB Designer examines the existing system's operation and determines how and why the system fails
- designer will spend time with end users
Overall purpose of the DB initial study:
- analysis of the company situation
- define problems and constraints
- define objectives
- define scope and boundaries
Figure 10-4: Summary of the Database initial study:
Analyse the company Situation:
Company situation describes the general conditions in which the company operates (organisational structure and its mission)
To analyse the company situation, the DB designer must discover what the company's operational components are, how they function and how they
interact.
Define Problems and Constraints:
Designer must find precise answers, as that of the managers and operators may differ
If the DB solves one problem, but causes another - no progress has been made
Real world usually intrudes to limit the design even more by imposing constraints
The DB designer must learn to distinguish between a perfect solution and a possible solution (having a R800k solution and 2 year plan to a R20k and 2
month plan, is not a solution)
The designer must find the SOURCE of the problem, not treat symptoms
Define Objectives:
Proposed DB system must help to solve at least the major problems identified during the problem discovery process
Thing to remember when examining procedures required to complete the design of the DBLC:
- DB design process is loosely related to the analysis and design of a larger system (data component is only one element of a larger IS)
- system analysts or programmers are designing the other system components (their activities create the procedures that help transform data from the
DB to useful info)
- DB design does not constitue a sequential process - rather it is an iterative process that provides continuous feedback designed to trace previous steps
Figure 10-6: Database Design Process:
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