1. Software Project Management
Lecture # 6

2. Outline Recap of topics from Chapter 23 Remaining topics of Chapter 23
The Software Equation
The Make/Buy Decision
Outsourcing
Project Scheduling (Chapter 24)
What is Scheduling?
What is Tracking?
Project Scheduling
Late Software Delivery & Project Deadlines
Project Scheduling Principles
People and Effort Relationship

3. Recap – “Software Estimation”
Software project planner must estimate the following important things before the project begins
How long it will take?
How much effort will be required?
How much money will be involved?
How many resources will be required?
People
Reusable software
Software/hardware
Risk consideration
In the beginning, project’s scope and feasibility are determined. The scope helps develop estimates using one or more techniques that fall into 2 broad categories
Decomposition
Empirical modeling

4. Recap – “Software Estimation”
Decomposition involves identifying major software function followed by estimates for each
Empirical techniques use empirically derived expressions for effort and time estimation
Software estimation can never be an exact science but use of good historical data and systematic techniques can improve estimation accuracy

5. The Software Equation Suggested by Putnam & Myers
It is a multivariable model
It assumes a specific distribution of effort over life of s/w project
It has been derived from productivity data collected for over 4000 modern-day s/w projects
E = [LOC x B0.333 / P]3 x (1/t4)
E = effort in person-months or person-years
B = special skills factor
P = productivity factor
t = project duration (months or years)

6. The Software Equation (Cont.)
P reflects
Overall process maturity
Management practices
Extent to which good s/w engg practices are used
Level of prog. Languages used
State of s/w environment
Skills & experience of team
Application complexity
Typical values of P
P= for a real-time embedded s/w
P= 10,000 - for telecomm. & systems s/w
P= 28,000 for business applications
Value of B
increases slowly as “the need for integration, testing, quality assurance, documentation and management skills grows”.
For small programs (KLOC=5 to 15), B= 0.16, for larger programs (KLOC=more than 70), B=0.39

7. The Software Equation (Cont.)
Software equation has two independent parameters
LOC t
Minimum dev. Time equations derived from software equation
tmin= 8.14 (LOC/P)0.43
in months for tmin> 6 months
E = 180 Bt3
In person-months for E>= 20 person-months

8. The Make/Buy decision
Often it is more cost effective to acquire rather than develop a software
Software managers have following options while making make/buy decisions
Software may be purchased (or licensed) off the shelf
“Full experience” or “partial experience” software components may be acquired and then modified as needed
Software may be custom-built by an outside contractor to meet specifications
Software criticality to be purchased and the end cost also affect acquisition process

9. The Make/Buy decision (Cont.)
For each of the discussed acquisition options, the Make/Buy decision is made based on following conditions
Will he software product be available sooner than internally developed software?
Will the acquisition cost plus cost of customization be less than cost of developing the software internally?
Will the cost of outside support (e.g., maintenance contract) be less than the cost of internal support?

10. Decision Tree Means 30% probability Estimated path cost
0.70 means 70% probability that job will be difficult

11. Decision Tree
Expected value of cost computed along each branch of the decision tree is:
where i is the decision tree path, for example,
For Build path
expected cost = 0.30($380K)+0.70($450K) = $429K
Similarly, for Reuse path, expected cost is $382K; for Buy path, it is $267K; for Contract path, it is $410K.
So the obvious choice is “to buy”
expected cost =
Σ (path probability)i x (estimated path cost)i

12. Outsourcing
Acquisition of software (or components) from a source outside the organization
Software engineering activities are contracted to a third party who does the work at lower cost and (hopefully) at higher quality
Software work within the company is reduced to contract management activity
Outsourcing is often a financial decision
Positive side
Cost saving can usually be achieved by reducing own resources (people & infrastructure)
Negative side
Company loses some control over the software and bears the risk of putting its fate in hands of a third party

13. Project Scheduling (Chap. 24 )

14. Introduction After the following have been achieved…
Process model selection
S/w engg. tasks identification
Estimation of amount of work & people
Risk consideration and knowing deadline
… the task is to create a setup for achieving the software engineering tasks. This setup is called ‘software project scheduling and tracking’

15. What is scheduling?
An activity that distributes estimated effort across the planned project duration by allocating the effort to specific software engineering task
Creating a network of software engineering tasks to complete the project and assign responsibilities of tasks and timing of tasks

16. What is Tracking?
Tracking is the process to make sure that all tasks are completed according to assigned responsibility and schedule.

17. Overview – Proper Scheduling
Proper Project Scheduling requires
All tasks should appear in the network
Interdependencies between tasks are indicated
Effort and timing are intelligently allocated to tasks
Resources are allocated to tasks
Closely spaced milestones are provided for progress tracking

18. Reasons for late software delivery
Unrealistic deadline established by some one outside the software development group & enforced
Changing customer requirements that are not reflected in schedule change
An honest underestimate of the amount of work and/or resources required
Risks that were not considered at project commencement
Technical difficulties not foreseen in advance
Miscommunication among project staff
A failure by project management to recognize that the project is falling behind schedule and a lack of action to correct the problem.

19. Dealing With Project Deadlines
Aggressive (actually unrealistic) deadlines are a fact of life in software business
If best estimates indicate that deadline is unrealistic Project Manager should
“Protect his/her team from undue (schedule) pressure… and reflect pressure back to its originators.”
Recommended steps for such situations:
Perform a detailed estimate using historical data from past projects. Determine effort and time required.
Use incremental model, develop a strategy that will deliver critical functionality within imposed deadline, but delay other functionality until later. Document the plan.

20. Dealing With Project Deadlines
Meet the customer and explain why deadline is unrealistic. Explain what is the new time required to complete this project.
Offer incremental development strategy as alternative. Offer some options.
We can increase the budget and have bring resources to get this job done in due time. But this contains increased risk of poor quality due to tight timeline.
We can remove some software functions, and provide remaining functionality later.
Dispense with reality and wish to complete software in due time.
By presenting solid estimates and references to past projects, it is likely that, negotiated version option 1 and 2 will be accepted by customer.

21. Project Schedule (Evolution)
Project schedules evolve over time
During early stages of project planning, a macroscopic schedule is developed
This schedule identifies all major process framework activities and the product functions to which they are applied
As the project proceeds, each entry on the macroscopic schedule gets refined into detailed schedule
Specific tasks are identified to achieve each activity and are scheduled

22. Project Scheduling - Basic Principles
Compartmentalization
Both the product and the process are decomposed into a number of manageable activities/tasks
Interdependency
Interdependencies among decomposed activities must be identified.
Some tasks can be performed in sequence and other can be done in parallel.
Some activities can not be performed without completion of another and some can be totally independent
Time Allocation
Each task must be allocated work units (person-days of effort)
Start and end time must be allocated considering interdependencies

23. Project Scheduling - Basic Principles
Effort validation
Project manager must ensure that no more than the allocated no. of people have been scheduled at any given time
Defined responsibilities
Every scheduled task must be assigned to a specific team member
Defined outcomes
Work products must be defined for every scheduled task
Defined milestones
Every task/group of tasks must be associated with a project milestone. A milestone is accomplished after one or more related work products has been reviewed for quality and approved

24. Relationship of People and Effort
Common Myth …
“If we fall behind schedule, we can always add more programmers and catch up later in the project!”
Doing so is often disruptive rather than productive causing further delays. Reasons:
learning time
teaching takes time away from productive work
added communication paths – increased complexity

25. Relationship of People and Effort
Putnam-Norden-Rayleigh (PNR) Curve indicates the relationship between effort applied and delivery time for a software project.
PNR curve was used to derive the software equation

26. Tmin=0.75Td td to Development Time
to = delivery time that will result in least effort expended
As we move left to to, i.e. as we try to accelerate delivery, curve rises nonlinearly
As we try to reduce accelerate delivery, curve rises sharply to left of td indicating, project delivery time can not be compressed much beyond 0.75td
As we try further, the project moves into impossible region and failure risk becomes high
Effort Cost Ed Eo
Impossible
Region
Tmin=0.75Td td to Development Time

27. PNR Curve & Software Eqn.
The software equation is derived from the PNR curve
It demonstrates a highly nonlinear relationship between time to complete project and human effort applied to the project
Lines of Code (L) is related to effort (E) and development time (t) as:
L = P x E 1/3 t 4/3
Rearranging the equation
E = L3 / P3t4