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Estimation techniques and software metrics


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Software Eng Subject / Tiu & Mark

Published in: Technology, Business

Estimation techniques and software metrics

  2. 2. How Bad are Our Projects? Only 34 percent of all projects succeed. The average project has a 43 percent cost overrun.
  3. 3. Why Projects FAIL Overlooked one or more of the crucial elements of project management.  Risk engineering and management  Human resource management  Effort and cost estimation  Project monitoring  Tracking and control  Time and financial management  Proper use of project management tools
  4. 4. What is Project Management? Did you say:  People skills  Software
  5. 5. What is Software ProjectManagement? Encompasses a set of activities that are performed during the phases of a typical software development project.
  6. 6. Software Project Manager Manage Software Projects
  7. 7. Software Project Manager  Continuously ensure that the software product is developed according to:  The client’s business requirements  Within allocated time  Within allocated budget
  8. 8. Elements of Software ProjectManagement The project itself The people working on the project The process used to produce the project deliverables The final product delivered to the client
  9. 9. Common Mistakes why ProjectsFAIL Project managers begin without knowing what the project is. Project managers do not have a plan. Project managers do not break the project down to manageable pieces.
  10. 10. Project Plan Is an important deliverable that must be developed carefully. Once written, the plan must be executed by the project manager. People involved should be well-versed Progress must be closely monitored by the manager
  11. 11. People Engaging the proper people to perform the prescribed tasks according to the project plan is important. Training people on the proper use of tools and techniques is essential. Communication and reporting must be well- defined to ensure frictionless environment. Transparent and continuous monitoring of people involved is critical for the early detection of problem symptoms.
  12. 12. Process and Phases Must be understood and defined because they determine deliverable and the efforts involved in their execution. An appropriate software life cycle model must be adapted for the project The development team needs to be knowledgeable regarding that model.
  13. 13. Project Management Activities Project management activitiesDuring project Estimation Developing the work plan:start-up Staffing activities, schedule, Resource acquisition resources, and budget Training allocationDuring project Quality assurance control Budget controlexecution Reporting and tracking Schedule control Metrics collection Requirements control Risk monitoring and mitigation Verification and validation Configuration management Documentation Process Improvement Problem resolution Subcontractor managementDuring project Product acceptance Archivingcloseout Staff reassignment Post-mortem evaluation and User training assessment Product installation Integration and conversion
  15. 15. Estimation One of the most critical activity during project startup Estimate the effort needed to complete the project Affects many resource aspects (financial and human) Must be realistic and accurate
  16. 16. Common Problems Underestimation  Project milestones cannot be met  What to do?  Leads to low employee morale, decline in reputation, and a stressful work environment Overestimation  Lead to losing the bid
  17. 17. ESTIMATION TECHNIQUE #1: Informal approaches  One or more expert opinions  Experiences from peers  Opinions of hired consultants
  18. 18. ESTIMATION TECHNIQUE #2: Decomposition Process  Break down the project into functional components  Ask potential developers of these components to provide their own estimates based on prior experiences
  19. 19. MACRO-LEVEL ESTIMATION Consider the software product as a whole
  20. 20. MICRO-LEVEL ESTIMATION Decompose the product into smallest possible components Estimate for those components Requires more time to produce, but accurate estimates are produced
  21. 21. CATEGORIES Black box-based / Requirements-based ET  Estimations are obtained once the software project scope is clearly defined in terms of the required functionalities  Function points and use case points estimation techniques Based on projected size of the final SW product in terms of lines of code (LOC)  COCOMO technique
  22. 22. How to solve a problem? When we have a problem that consists of two particular aspects, we should consider taking care about each aspect separately. Once the first of problems is solved, we can turn to another. After that, everything left is to check whether the particular solutions work well together with greater problem.
  23. 23. Back to measuring applicationcomplexity … The analysis based on function points can be compared to slicing the problem into smaller parts.
  24. 24. Function Points (to simplify) FP is a standard method for quantifying the software deliverable based upon the user view, where:  User is any person or thing that communicates or interacts with the software at any time  User View is the Functional User Requirements as seen by the user  Functional user requirements describe what the software shall do, in terms of tasks and services.
  25. 25. Five Functional Components INTERNAL LOGIC FILES (ILF)  Files created and maintained within the application EXTERNAL INTERFACE FILES (EIF)  Files that are owned and are exchanged by other systems EXTERNAL INPUTS (EI)  Inputs that affect the control flow and internal logic of the application leading to the creation and maintenance of data EXTERNAL OUTPUTS (EO)  Data leaving the application to different devices, files or external systems EXTERNAL INQUIRIES (EQ)
  26. 26. How to perform Function PointsAnalysis? Basically people solve problems by dividing them into smaller parts. Instead of trying to evaluate the application as a whole, we need to rate each of the selected groups. How exactly to do it? We need to classify the complexity of each category.
  27. 27. Function Points Analysis (FPA) We have three possibilities. COMPLEXITY COMPONENT SIMPLE AVERAGE COMPLEX External Input 3 4 6 External Output 4 5 7 User Inquiry 3 4 6 External Interface File 7 10 15 Internal Logic File 5 7 10 Then, the whole “problem” is to sum the values. A total of them represents the number of application’s function points.
  28. 28. Function Point Metrics SIMPLE AVERAGE COMPLEX How many? How many? How many? Product Product Product Weight Weight Weight Factor Factor FactorExternal Input 3 1 3 4 2 8 6 1 6External Output 4 3 12 5 0 0 7 1 7User Inquiry 3 1 3 4 1 4 6 0 0External Interface File 7 0 0 10 0 0 15 3 45Internal Logic File 5 0 0 7 0 0 10 1 10TOTAL 18 12 68NO. of FPs 18 + 12 + 68 = 98 function points
  29. 29. CASE STUDY STOCK CONTROL SYSTEM – estimating the time needed to develop this applicationLets imagine a company which sells goods on thephone - if agents call the customers, customers callthe agents, and so on - business operatessuccessfully, but there comes a time for putting thewhole in order. There occurs a need for developinga system able to control the whole stock, fromorders to payments. Our thing is to estimate howcomplex such system can be and - after that - tryto predict how long it would take to develop it.
  30. 30. HELP??.. :’( At first, we should pay attention to the functionality – what exactly the system should be able to do. Then, let us group functions into five categories. Let math do the last thing. (^_^)
  31. 31. Let’s predict every function’s complexity issimple … Category Multiplier Weight FactorExternal Inputs 4 3External Outputs 4 4External InQuiries 3 3Internal Logic Files 4 5 4 * 3 + 4 * 4 + 3 * 3 + 4 * 5 = 57 [FunctionHowPoints]takes to produce 57 function points? long it 57 * 8 = 456 [hours]The answer? - The estimate for developing the application wouldtake about 456 hours of work.
  32. 32. Technical factors affectingcomplexity of software projects Reliable backup and recovery needed Data communications needed Distributed functions required Performance required Heavily used configuration Real-time data entry needed Ease of use
  33. 33. Technical factors affectingcomplexity of software projects Real-time update needed Complexity of the interfaces Complexity of the processing Reusability Ease of installation Multiple sites Easy to change
  35. 35. Use Case Points
  36. 36. Use Case Points introduced by Gustav Kamer in 1993 Extension of the FP method based on the use cases existing in the use case model of a software system
  37. 37. Categories of actors:  Simple – are other systems that communicate with your software via a pre- defined API. Complex – has more than 10 transactions
  38. 38. Categories of actors:  Average - can either be human beings interacting in a well defined protocol, or they could be systems that interact through a more complex or flexible API.
  39. 39. Categories of actors:  Complex - users who interact with the software through a graphical user interface are complex actors - users who interact with the system in unpredictable ways
  40. 40. Categories of use cases:  Simple – at most 3 transactions  Average – has 4 to 7 transactions  Complex – has more than 7 transactions
  41. 41. Unadjusted Actor Weight(UAW) sum of complexity values assigned to each actor sum of all actor weights
  42. 42. e.g.
  43. 43. Unadjusted Use Case Weight(UUCW) sum of complexity values assigned to each use case
  44. 44. e.g.
  45. 45. Unadjusted Use Case Point(UUCP) the unadjusted size of the overall system UUCP= UAW + UUCWe.g. UUCP = 560 + 40 =600
  46. 46. Adjusted Use Case Points(AUCP) total effort to develop a system in respect to the different factors impacting Technical Complexity Factor and Environmental Factor AUCP = (UAW + UCCW * TCF * EF)
  47. 47.  Technical Complexity Factor - Sum of all the weighted values computed for each of the 13 technical factors which are mainly related to the product and its complexity in terms of functional and non-functional requirements. TCF = 0.6 + (0.01 * TF)
  48. 48. e.g. TCF = 0.6 + (0.01 * 42) = 1.02
  49. 49.  Environmental Factor - related to the people, process and project aspects of the software EF = 1.4 - (-0.03 * EF)
  50. 50. e.g. EF = 1.4 + (-0.03 * 17.5) = 1.4 + (-0.03 * 17.5) = 0.89
  51. 51. COCOMO
  52. 52. Constructed Cost Model(COCOMO) introduced by Barry Boehm in 1981 provides an estimate of the effort in person- months needed to develop a software product Based on the estimation of the size of the software in terms of the number of lines of codes
  53. 53. Types of Software1. Organic Products -are relatively small and simple2. Semi-detached -are average in size and simplicity
  54. 54. 3. Embedded - complex in the sense that they must meet the constraints of their embedding environment and interfaces, including software and hardware
  55. 55. 3 Versions of COCOMO Basic - provides an estimate of the effort as a function of an estimate of the program size. -the development effort and the development duration are calculated on the basis of the estimated DSI. E = a * Sizeb D = c * Ed P = E/D
  56. 56.  Intermediate -The same basic equation for the model is used, but fifteen cost drivers are rated on a scale of very low to very high to calculate the specific effort multiplier and each of them returns an adjustment factor which multiplied yields in the total EAF (Effort Adjustment Factor). E = a * Size * EAF
  57. 57.  Detailed -computes effort as a function of program size and a set of cost drivers weighted according to each phase of the software lifecycle.
  58. 58. 4 phases of Detailed COCOMO 1. Requirements Planning and Product design 2. Detailed Design 3. Code and Unit Test 4. Integration and Test
  59. 59. Thank you.. :P By : wa lng.. :D