Software Project Management

Software Project Management

Software Project Management

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Presentation Transcript

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= 2000 - 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

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. 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