IS 421 Information Systems Analysis James Nowotarski 4 November 2002.
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Transcript of IS 421 Information Systems Analysis James Nowotarski 4 November 2002.
• Recap data flow diagramming• Understand steps required for creating a work
plan• Discuss Assignment 5
Today’s Objectives
Course Map
Contents
1. Introduction
Planning Phase2. Project Initiation3. Project Management
Analysis Phase4. Systems Analysis5. Gathering Information6. Process Modeling7. Data Modeling
1 2 3 4 6 7 8 9 10 115
Assignments
QuizzesFinal
Week
CoreExamReview
Topic Duration
• Prof. Burns 30 minutes
• DFD Recap 30 minutes
• Quiz 45 minutes
*** Break 15 minutes
• Project management 45 minutes
• Assignment 5 Intro 15 minutes
Today’s agenda
Topic Duration
• Prof. Burns 30 minutes
• DFD Recap 30 minutes
• Quiz 45 minutes
*** Break 15 minutes
• Project management 45 minutes
• Assignment 5 Intro 15 minutes
Today’s agenda
Process modeling
Prepare use cases
use case reports
Create DFDs
UsersUsers
data flow diagrams
businessprocess
info
• Easier for users to work with than DFDs
• Info gathered through interviews, JAD, etc.
To Design
DFD Balancing
0
SystemName
Input AEntity 1Entity 1
Entity 2Entity 2
Input B
Output CEntity 3Entity 3
DFD Balancing
Input A
1
General Process
AAA
Entity 1Entity 1
Entity 2Entity 2
Output C Entity 3Entity 3
Input B
3
General Process
CCC
2
General Process
BBB
4
General Process
DDD
Data Flow B
D1 Data Store 1 D2 Data Store 2
Data Flow D
Data Flow A
Data Flow A
Data Flow C
Data Flow C
Which is best?
CustomerCustomer Changeaddress
1Address change info
D1 Customer InformationAddress change info
CustomerCustomer Changeaddress
1Address change info
D1 Customer InformationAddress change info
CustomerCustomer Changeaddress
1 Address info
D1 Customer InformationAddress change info
Address change info
Scenario: A customer notifies a magazine publisher of a change of address.
“For clarity, it is better practice to draw two separate data flows” (p. 149)
• Manual vs. Automated processes• Chronological order• Can same external entity be shown more than
once (yes, to avoid crossing lines)
DFD Issues
DFD Step-by-Step(8) Grades are reported back to students via a course web page created from the spreadsheet.
Professor
CampusConnect
1
Downloadstudent info
Courseroster
Course roster 2
Maintainstudents
D2 StudentStudent info
Student info
3
Maintainassignments
D1 Assignment
Assignmentinfo
Assignment info
Students 4
Collectassignment
Completedassignment
Compeleted assigments
5
Distributeassignment
Assignment info
Assignmentinfo
Completed assignments
6
Gradeassignments
Assignmentinfo
Studentinfo
D3 Grade
Gradeinfo
Students
7
Reportgrade
Student id
Grade info
Gradeinfo
Topic Duration
• Prof. Burns 30 minutes
• DFD Recap 30 minutes
• Quiz 45 minutes
*** Break 15 minutes
• Project management 45 minutes
• Assignment 5 Intro 15 minutes
Today’s agenda
Topic Duration
• Prof. Burns 30 minutes
• DFD Recap 30 minutes
• Quiz 45 minutes
*** Break 15 minutes
• Project management 45 minutes
• Assignment 5 Intro 15 minutes
Today’s agenda
Key Definitions
• Project management is the process of planning and controlling the development of a system within a specified timeframe at a minimum cost with the right functionality.
Management Challenges in Analysis
• Political difficulties– Especially in larger projects, where the new system will
serve several, possibly conflicting, interest groups• Communication problems
– People of different backgrounds, vocabularies being asked to work together
– Users in particular may struggle to understand the technical-looking outputs of the Analysis phase
• Scope management • Analysis paralysis
– Easy to become mired in detail, not know when to finish• “Prematurely physical”
Create the work plan
Usersrequirements 1
Negotiatereqts
negotiatedrequirements
2
Decom-pose
workbreakdownstructure
4
Estimateresources
workmonths
3
Estimatesize
deliverablesize
5
Developschedule
schedule
Iterate as necessary
Estimating a Project Based on Industry Information
Planning Analysis Design Implementation
IndustryStandardFor Web 15% 20% 35% 30%Applications
TimeRequired 4 5.33 9.33 8in PersonMonths
Some Courses at DePaul
• SE 468: Software Measurement and Estimation– Software metrics. Productivity, effort and defect models.
Software cost estimation. PREREQUISTE(S):CSC 423 and either SE 430 or CSC 315 or consent
• SE 477: Software and System Project Management– Planning, controlling, organizing, staffing and directing
software development activities or information systems projects. Theories, techniques and tools for scheduling, feasibility study, cost-benefit analysis. Measurement and evaluation of quality and productivity. PREREQUISTE(S):SE 465 or CSC 315
Estimation Trade-offs
• Time– Months
• Effort– Person-months
• Size– Function points
– Lines of code
Getting the Right Numbers for Estimation
• Prior projects– Past experience
– Industry standards
• Detailed analysis
Estimating Schedule Time
• Rule of thumb for estimation
Schedule Time (months)
=
3.0 * person-months1/3
Timeboxing Steps
• Set delivery date
– Deadline should not be impossible
– Should be set by development group• Prioritize features by importance• Build the system core• Postpone unfinished functionality• Deliver the system with core functionality• Repeat steps 3-5 to add refinements and
enhancements
Margins of Error in Cost and Time Estimates
Typical margins of Error for
Well-done Estimates
Phase Deliverable Cost (%)time (%)
Planning System Request 400 60Project Plan 100 25
Analysis System Proposal 5015
Design System Specification 25 10
Source: Boehm et al. (1995)
Relative Cost to Fix an Error
It costs 50x more to fix an error discovered in production than in Analysis phase
Phase in which error detected
Analysis Design Code Unit test Acceptancetest
Production
0.1
0.2
0.5
1
2
5
10
20
50
Rel
ati v
e c o
s t t
o f
ix
Tracking Tasks Using Gantt Chart
Go to Library
Go to Bookstore
Select and Purchase Book
Skim Book
Write Phase One
Read Book Carefully
Write Phase Two
Action Week 2 3 4 5 6 7 8 9 10 11 12 13
Standards
• Examples– Formal rules for naming files
– Forms indicating goals reached (see page 75)
– Programming guidelines
Classic Mistakes
• Overly optimistic schedule• Failing to monitor schedule• Failing to update schedule• Adding people to a late project• Scope creep• Lack of change control
Topic Duration
• Prof. Burns 30 minutes
• DFD Recap 30 minutes
• Quiz 45 minutes
*** Break 15 minutes
• Project management 45 minutes
• Assignment 5 Intro 15 minutes
Today’s agenda