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SA&D lecture2, Approaches to Structured Analysis and Design and to the…
SA&D lecture2
Developing Information Systems
System Development Methodology is a standard process followed in an organization to conduct all the steps necessary to
analyze, design, implement, and maintain information systems.
Approaches to Structured Analysis and Design and to the Systems Development Life Cycle
Traditional systems development life cycle
The systems development life cycle is a phased
approach to solving business problems.
Developed through the use of a specific cycle of
analyst and user activities
Each phase has unique user activities.
It consists of 7 steps:
Identifying problems,opportunities, and objectives
activity
Interviewing user management
Summarizing the knowledge obtained
Estimating the scope of the project
Documenting the results
Output
Feasibility report
containing problem definition and objective summaries from which management can make a decision on
whether to proceed with the proposed project
Determining human infromation requirements
activiy
Interviewing
Sampling and investing hard data
Questionnaires
Observe the decision maker’s behavior and environment.
Prototyping
Learn the who, what, where, when, how, and why of the current system.
output
The analyst understands how users accomplish their work when interacting with a computer; and begin to know how to make the new system more useful and usable. The analyst should also know the business functions and have complete information on the people, goals, data, and procedure involved.
Analyzing system needs
Activity
Create data flow, activity, sequence diagrams
Complete the data dictionary.
3.Analyze the structured decisions made using structured english, decision tables and decesion trees.
Prepare and present the system proposal that summarizes what has been found out about the users, usability and usefulness of current systems; provide cost-benefits analyses of alternatives
Output
Recommendation on what, if anything, should be done
Designing the recommended system
activity
1.Design procedures for data entry.
2.Design the human-computer interface.
3.Design system controls.
4.Design database and/or files.
5.Design backup procedures.
output
Model of the actual system
Implementing and documenting software
activity
1.System analyst works with programmers to develop any original software.
2.Works with users to develop effective documentation.
3.Programmers design, code, and remove syntactical errors from computer programs.
Document software with help files, procedure manuals, and Web sites with Frequently Asked Questions.
output
Computer programs
System documentation
Test and maintaining the sysetm
activity
1.Test the information system.
2.System maintenance.
3.Maintenance documentation.
output
Problems, if any
Updated programs
Problems, if any
Implementing and evaluating the system
activity
2.Analyst plans smooth conversion from old system to new
system.
3.Review and evaluate system.
1.Train users.
output
Trained personnel
Installed system
Object-oriented systems analysis and
design
Alternate approach to the structured approach of the SDLC
that is intended to facilitate the development of systems
that change rapidly in response to dynamic business environments
Analysis is performed on a small part of the system
followed by design and implementation.
The cycle repeats with analysis, design, and implementation of the next part and this repeats until the project is complete.
Examines the objects of a system
Unified Modeling Language (UML) Phases
Define the use case model:
Use case diagram
Use case scenarios
Create UML diagrams.
3.Develop class diagrams.
4.Draw statechart diagrams.
5.Modify the UML diagrams.
6.Develop and document the system.
CASE tools
CASE tools are productivity tools for systems analysts that have been created explicitly to improve their routine work through the use of automated support.
Reasons for using CASE tools
Increasing analyst productivity
Improving analyst-user communication
Integrating life cycle activities
Case Tool Classifications
Upper CASE tools
perform analysis and design.
Create and modify the system design.
Help in modeling organizational requirements and defining system boundaries.
Lower CASE tools
generate programs from CASE
design.
Lower CASE tools generate computer
source code
from the CASE design.
Source code is usually generated in several
languages.
Decreases maintenance time
Generates error-free code
The Agile Approach
values
Communication
Simplicity
Feedback
Feedback
Principles
Adaptive rather than predictive
Emphasize (focus on) people rather than roles
Self-adaptive processes
Core practicies
Four Agile Resources
Resources are adjusted to ensure successful project completion.
Time
Quality
Cost
Scope
Five Stages of Agile Development
1.Exploration
2.Planning
3.Iterations to the first release
4.Productionizing
5.Maintenance
The Impact of Maintenance
Maintenance is performed for two reasons:
Removing software errors
Enhancing existing software
Over time the cost of continued maintenance will be greater than that of creating an entirely new system. At that point it becomes more feasible to perform a new systems study.