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Software Project Management. Lecture 1 Introduction to Software Project Management. Overview. Software engineering Software project management Formal methods. Software Crisis. Faulty software Delay in completion time Over budgeted Difficult to maintain software. Some UK projects.

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Software Project Management


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    1. Software Project Management Lecture 1 Introduction to Software Project Management

    2. Overview • Software engineering • Software project management • Formal methods

    3. Software Crisis • Faulty software • Delay in completion time • Overbudgeted • Difficult to maintain software

    4. Some UK projects • Home Office asylum seeker Casework system: £80m; abandoned 2001 (Siemens). • Pathway UK benefits identity card system: abandoned 1999 with £1bn losses (ICLFujitsu). • Datacentre for UK cabinet office: £85m, cancelled in 2004 (ITNET). • MRC Laboratory of Molecular Biology, FAMIS purchasing system: £55m; ‘operating failure’ (LogicaGMC). • UK e-University: £62m; abandoned 2004 (Sun, though only £20m of the full figure).

    5. American experience • 25% of development projects are abandoned • probability of cancellation rises to 50% for largest developments • average project overshoots schedule by 50% • 75% of systems are regarded as ‘operating failures’ U.S. Bureau of Labor Statistics, 1997

    6. Some important facts • Relative cost of the software in a system is growing • Increase in demand for software • Increase in size and complexity of software • Increase in performance of hardware

    7. Software Engineering An initial, loose definition: “the establishment and use of sound engineering principles in order to obtain, economically, software that is reliable and works efficiently on real machines” [Bauer, 1969]

    8. A more useful definition “The application of scientific and engineering efforts to 1. transform an operational need into a system through the use of an iterative process of definition, analysis, design, test, and validation; 2. ensure the compatibility of all interfaces […]; 3. integrate reliability, maintainability, disposability, […] to meet cost, schedule, and technical performance objectives.” [Blanchard, 1998]

    9. Software Engineering • Aimed at large software • Systematic and well-defined techniques, methodologies and tools • To design, code, test and maintain quality software • Within a resource constrained environment

    10. Large Software • Developed by more than one person • Effective communications are important – standards, documentation, etc • Management issues • Techniques and methodologies are useful only if automated systems can be built upon them

    11. Phases of Software Development • Requirements analysis and specification • Design • Coding • Testing • Installation • Maintenance

    12. Some important observations • Maintenance is the most expensive phase and coding is the least expensive phase • The earlier the detection of faults, the less expensive the correction of faults

    13. Characteristics of software • Simple and elegant mathematical representation • Logic intensive • Cannot have partial completion • Design costs are relatively expensive

    14. What is a project? • Key characteristics of a project: • A planned activity • Specific objectives or products • Work to be carried out in several phases • Limited resources • Deadline • Large and complex

    15. Major differences between software products and hardware products • Progress of software development is not obviously visible • Modifications of software products are more easy and flexible • Software products are usually more complex than the hardware products in terms of development or construction cost

    16. Major processes in developing a software system • Feasibility study • Project planning • Project execution

    17. Feasibility Study • Analyze the general requirements, costs and the functionalities and services provided by the system to be developed • Aimed to determine whether a system should be developed or not • Can be viewed as a project itself

    18. Important factors in planning a software project • To know the nature of the system to be developed • A management information system or a control system • To know clearly the objectives and products of the project • How to evaluate the objectives and products after the completion of the project

    19. What is management? • Management involves the following activities: • Planning • Staffing • Innovating • Directing • Monitoring • Liaising • …?

    20. What is software project management? • Understand the characteristics of software products • Understand what is meant by a project • Understand what is meant by management

    21. Common problems with software projects • Lack of quality standards and measures • Lack of measurable milestones • Difficult to make the progress visible • Poor communications • Poor documentation • Frequent changes of requirements • Over budget and late delivery of software

    22. Major issues of software project management to be covered • Software development models • Software size and cost estimation • Software project planning • Software risk management • Resource allocation • Standards: ISO 9000 and CMM • Performance tracking and reporting

    23. Major issues of software project management to be covered (cont’d) • Software project configuration management • Software project team management

    24. Main problems encountered with requirements and specifications • Ambiguous • Incomplete • Inconsistent

    25. Main problems encountered with requirements and specifications (cont’d) • To overcome these problems via • Formality – achieving precision • Abstraction – concentrating on essential parts

    26. Formal Methods • Mathematically based techniques • Providing a precise and concise language • Supporting formality • Supporting abstraction • Supporting logical reasoning • May support automation

    27. Example: traffic light control • Simple 4-way crossroads • Traffic lights control each entry • Roads run North-South and East-West N

    28. type Light == red | redamber | green | amber, Junction :: ns : Light ew : Light timer : Nat value nextLight : Light → Light nextLight(l) is case l of red → redamber, redamber → green, green → amber, amber → red end,

    29. limit : Junction → Nat limit(j) is if ns(j) isin {amber, redamber} \/ ew(j) isin {amber, redamber} then 1 else 4 end, next : Junction → Junction next(j) is if limit(j) ≤ timer(j) then mk_Junction(nextLight(ns(j)), nextLight(ew(j)), 0) else mk_Junction(ns(j), ew(j), timer(j) + 1) end, safe : Junction → Bool safe(j) is ~ (ns(j) = green /\ ew(j) =green)

    30. Critical properties • Safety: • Not both green at the same time: G(safe(junction)) i.e. Globally (in all states), the junction is safe • Liveness: • In each direction, lights will eventually go green: G(F(ns(junction) = green)) i.e. Globally, in the Future, North-South is green /\ G(F(ew(junction) = green))

    31. Is the junction safe and live? • Safe? – depends on what state it starts in • Live? – yes We can model check the specification to prove these.

    32. transition_system [T] local junction : Junction := mk_Junction(red, red, 0) in [change] true ==> junction' = next(junction) end ltl_assertion [safe] T |- G(safe(junction)), [live_ns] T |- G(F(ns(junction) = green)), [live_ew] T |- G(F(ew(junction) = green))

    33. Counterexample for 'safe': ======================== Step 0: junction = mk_Junction(red, red, 0) ------------------------ Step 1: junction = mk_Junction(red, red, 1) ... Step 4: junction = mk_Junction(red, red, 4) ------------------------ Step 5: junction = mk_Junction(redamber, redamber, 0) ... Step 7: junction = mk_Junction(green, green, 0) Summary: The assertion 'safe' is invalid. The assertion 'live_ns' is valid. The assertion 'live_ew' located at is valid.

    34. What are formal methods for? • Clarify and fix requirements • Support early analysis: • Static analysis • Testing • Model checking • Proof • Provide a basis for implementation

    35. Specification languages • The traffic light example was written in RAISE • There are many formal methods, some general purpose, some specialised

    36. A good slogan • You may not be able to avoid making mistakes … • But you must find them before they cost too much!

    37. Modelling • Modern software engineering is based on making models • A formal model (eg in RAISE) supports more analysis than in informal one (eg in UML) • Increasingly, implementations will be derived from models: programmers will be obsolete

    38. References • Hughes, B., and Cotterell, M. (1999) Software Project Management, McGraw Hill • Dean, C.N., and Hinchey, M.G. (1996) Teaching and Learning Formal Methods, Academic Press • Sommerville, I. (2001) Software Engineering, Pearson Education.

    39. References • RAISE: http://www.iist.unu.edu/raise • Dines Bjørner (2006) Software Engineering, Springer