COSC 4406 Software Engineering Haibin Zhu Ph D

COSC 4406 Software Engineering Haibin Zhu, Ph. D. Dept. of Computer Science and mathematics, Nipissing University, 100 College Dr. , North Bay, ON P 1 B 8 L 7, Canada, haibinz@nipissingu. ca, http: //www. nipissingu. ca/faculty/haibinz 1

Lecture 14 Project Estimation and Scheduling Ref. Chap 26 & 27 (7 th Edition) 2

Software Project Planning The overall goal of project planning is to establish a pragmatic strategy for controlling, tracking, and monitoring a complex technical project. Why? So the end result gets done on time, with quality! 3

Project Planning Task Set-I n n n Establish project scope Determine feasibility Analyze risks n n Risk analysis is considered in detail in Chapter 25. Define required resources n n n Determine require human resources Define reusable software resources Identify environmental resources 4

Project Planning Task Set-II n Estimate cost and effort n n Decompose the problem Develop two or more estimates using size, function points, process tasks or use-cases Reconcile the estimates Develop a project schedule n n Establish a meaningful task set Define a task network Use scheduling tools to develop a timeline chart Define schedule tracking mechanisms 5

Estimation n Estimation of resources, cost, and schedule for a software engineering effort requires n n experience access to good historical information (metrics the courage to commit to quantitative predictions when qualitative information is all that exists Estimation carries inherent risk and this risk leads to uncertainty 6

Write it Down! Project Scope Estimates Risks Schedule Control strategy Software Project Plan 7

To Understand Scope. . . n n n Understand the customers needs understand the business context understand the project boundaries understand the customer’s motivation understand the likely paths for change understand that. . . Even when you understand, nothing is guaranteed! 8

What is Scope? n Software scope describes n n n the functions and features that are to be delivered to end-users the data that are input and output the “content” that is presented to users as a consequence of using the software the performance, constraints, interfaces, and reliability that bound the system. Scope is defined using one of two techniques: n n A narrative description of software scope is developed after communication with all stakeholders. A set of use-cases is developed by end-users. 9

Resources 10

Project Estimation n n Project scope must be understood Elaboration (decomposition) is necessary Historical metrics are very helpful At least two different techniques should be used Uncertainty is inherent in the process 11

Estimation Techniques n n Past (similar) project experience Conventional estimation techniques n n task breakdown and effort estimates size (e. g. , FP) estimates Empirical models Automated tools 12

Estimation Accuracy n Predicated on … n n the degree to which the planner has properly estimated the size of the product to be built the ability to translate the size estimate into human effort, calendar time, and dollars (a function of the availability of reliable software metrics from past projects) the degree to which the project plan reflects the abilities of the software team the stability of product requirements and the environment that supports the software engineering effort. 13

Functional Decomposition Statement of Scope Perform a Grammatical “parse” functional decomposition 14

Conventional Methods: LOC/FP Approach n n compute LOC/FP using estimates of information domain values use historical data to build estimates for the project 15

Example: LOC Approach Average productivity for systems of this type = 620 LOC/pm. The total LOC: 33200 Burdened labor rate =$8000 per month, the cost per line of code is approximately $13. Based on the LOC estimate and the historical productivity data, the total estimated project cost is $461, 000 (33200*13*1. 068) and the estimated effort is 54 person-months. 16

Example: FP Approach The estimated number of FP is derived: FPestimated = count-total * [0. 65 + 0. 01 * ∑(Fi)] If count-total = 320, ∑(Fi) = 52, then FPestimated = 375 If organizational average productivity = 6. 5 FP/pm. The burdened labor rate = $8000 per month, the cost per FP is approximately $1230. Based on the FP estimate and the historical productivity data, the total estimated project cost is $461, 000 and the estimated effort is 58 person-months. 17

Process-Based Estimation Obtained from “process framework” framework activities application functions Effort required to accomplish each framework activity for each application function 18

Process-Based Estimation Example Based on an average burdened labor rate of $8, 000 per month, the total estimated project cost is $368, 000 and the estimated effort is 46 person-months. 19

Estimation with Use-Cases n LOC estimate = N*LOCavg+[(Sa/Sh-1) +(Pa/Ph-1)]*LOCadjust n n n n N: actual number of use-cases LOCavg : historical average LOC per use-case for this type of subsystem LOCadjust : an adjustment based on n percent of LOCavg where n is defined locally Sa: actual scenarios per use-case Sh: Average scenarios per use-case for this type of subsystem Pa: Actual pages per use-case Ph: Average pages per use-case for this type of subsystem 20

Estimation with Use-Cases LOC estimate (3366) = N(6)*LOCavg(560)+[(Sa(10)/Sh(12)-1) +(Pa(6)/Ph(5)-1)]*LOCadjust(60) Using 620 LOC/pm as the average productivity for systems of this type and a burdened labor rate of $8000 per month, the cost per line of code is approximately $13. Based on the use-case estimate and the historical productivity data, the total estimated project cost is $552, 000 and the estimated effort is 68 person-months. 21

The Software Equation A dynamic multivariable model E = [LOC x B 0. 333/P]3 x (1/t 4) where • E = effort in person-months or person-years • t = project duration in years • B = “special skills factor” • P = “productivity parameter” • P = 2000 for RT embedded • P = 10, 000 for tele comm/system software (sw) • P = 28, 000 for business sw 22

Computation n n n tmin = 8. 14 (LOC/P)0. 43 (>6 months, in months) E=180 Bt 3 (>= 20 pms) (t in years) For the CAD project B = (Bsmall + Blarge) /2 =(0. 16+0. 39)/2 =0. 28 tmin = 8. 14 (33200/12000)0. 43 =12. 6 months = 1. 5 years E=180*0. 28*(1. 05)3 = 58 pms 23

Estimation for OO Projects-I n n Develop estimates using effort decomposition, FP analysis, and any other method that is applicable for conventional applications. Using object-oriented analysis modeling (Chapter 8), develop use-cases and determine a count. From the analysis model, determine the number of key classes (called analysis classes in Chapter 8). Categorize the type of interface for the application and develop a multiplier for support classes: n n n Interface type No GUI Text-based user interface GUI Complex GUI Multiplier 2. 0 2. 25 2. 5 3. 0 24

Estimation for OO Projects-II n n n Multiply the number of key classes (step 3) by the multiplier to obtain an estimate for the number of support classes. Multiply the total number of classes (key + support) by the average number of work-units per class. Lorenz and Kidd suggest 15 to 20 person-days per class. Cross check the class-based estimate by multiplying the average number of work-units per use-case 25

The Make-Buy Decision 26

Computing Expected Cost expected cost = (path probability) x (estimated path cost) i i For example, the expected cost to build is: expected costbuild = 0. 30 ($380 K) + 0. 70 ($450 K) = $429 K similarly, expected costreuse expected costbuy expected costcontr = $382 K = $267 K = $410 K 27

Project Scheduling n Why Are Projects Late? n n n n an unrealistic deadline established by someone outside the software development group changing customer requirements that are not reflected in schedule changes; an honest underestimate of the amount of effort and/or the number of resources that will be required to do the job; predictable and/or unpredictable risks that were not considered when the project commenced; technical difficulties that could not have been foreseen in advance; human difficulties that could not have been foreseen in advance; miscommunication among project staff that results in delays; a failure by project management to recognize that the project is falling behind schedule and a lack of action to correct the problem 28

Scheduling Principles n n n compartmentalization—define distinct tasks interdependency—indicate task interrelationship effort validation—be sure resources are available defined responsibilities—people must be assigned defined outcomes—each task must have an output defined milestones—review for quality 29

Effort and Delivery Time 30

Effort/Delivery time Based of Software Equation n n L = P×E 1/3×t 4/3 n L is the number of lines of code; n E is development effort in personmonths; n P is a productivity parameter that reflects a variety of factors that lead to high-quality software engineering work; n t is the project duration in calendar months. E= L 3/(P 3×t 4) If 148 = 330003/(P 3*164), Then 50 = 330003/(P 3*214) E. G. Suppose a Complex Real-time software wit 33, 000 LOC, used 1. 3 year? If we decide to use 1. 75 years, what is the Effort? E t 12 PY(148 PM) 1. 3 years (16 months) 4. 17 PY (50 months) 1. 75 years (21 months) 31

Effort Allocation 40 -50% 15 -20% n “front end” activities n n n construction activities n n 30 -40% customer communication analysis design review and modification coding or code generation testing and installation n unit, integration white-box, black box regression 32

Defining Task Sets n n determine type of project assess the degree of rigor required identify adaptation criteria select appropriate software engineering tasks 33

Task Set Refinement 1. 1 Concept scoping determines the overall scope of the project. Task definition: Task 1. 1 Concept Scoping 1. 1. 1 Identify need, benefits and potential customers; 1. 1. 2 Define desired output/control and input events that drive the application; Begin Task 1. 1. 2. 1 FTR: Review written description of need FTR indicates that a formal technical review (Chapter 26) is to be conducted. 1. 1. 2. 2 Derive a list of customer visible outputs/inputs 1. 1. 2. 3 FTR: Review outputs/inputs with customer and revise as required; endtask Task 1. 1. 2 1. 1. 3 Define the functionality/behavior for each major function; Begin Task 1. 1. 3. 1 1. 1. 3. 2 Derive a model of functions/behaviors; 1. 1. 3. 3 is refined to FTR: Review output and input data objects derived in task 1. 1. 2; FTR: Review functions/behaviors with customer and revise as required; endtask Task 1. 1. 3 1. 1. 4 Isolate those elements of the technology to be implemented in software; 1. 1. 5 Research availability of existing software; 1. 1. 6 Define technical feasibility; 1. 1. 7 Make quick estimate of size; 1. 1. 8 Create a Scope Definition; end. Task definition: Task 1. 1 34

Define a Task Network 35

Timeline Charts Tasks Week 1 Week 2 Week 3 Week 4 Week n Task 1 Task 2 Task 3 Task 4 Task 5 Task 6 Task 7 Task 8 Task 9 Task 10 Task 11 Task 12 36

Use Automated Tools to Derive a Timeline Chart 37

Schedule Tracking n n n conduct periodic project status meetings in which each team member reports progress and problems. evaluate the results of all reviews conducted throughout the software engineering process. determine whether formal project milestones (the diamonds shown in Figure 24. 3) have been accomplished by the scheduled date. compare actual start-date to planned start-date for each project task listed in the resource table (Figure 24. 4). meet informally with practitioners to obtain their subjective assessment of progress to date and problems on the horizon. use earned value analysis (Section 24. 6) to assess progress quantitatively. 38

Progress on an OO Project-I n Technical milestone: OO analysis completed n n n All classes and the class hierarchy have been defined and reviewed. Class attributes and operations associated with a class have been defined and reviewed. Class relationships (Chapter 8) have been established and reviewed. A behavioral model (Chapter 8) has been created and reviewed. Reusable classes have been noted. Technical milestone: OO design completed n n n The set of subsystems (Chapter 9) has been defined and reviewed. Classes are allocated to subsystems and reviewed. Task allocation has been established and reviewed. Responsibilities and collaborations (Chapter 9) have been identified. Attributes and operations have been designed and reviewed. The communication model has been created and reviewed. 39

Progress on an OO Project-II n Technical milestone: OO programming completed n n Each new class has been implemented in code from the design model. Extracted classes (from a reuse library) have been implemented. Prototype or increment has been built. Technical milestone: OO testing n n n The correctness and completeness of OO analysis and design models has been reviewed. A class-responsibility-collaboration network (Chapter 8) has been developed and reviewed. Test cases are designed and class-level tests (Chapter 14) have been conducted for each class. Test cases are designed and cluster testing (Chapter 14) is completed and the classes are integrated. System level tests have been completed. 40

Summary n n n n Basic concepts Resources Project estimation Decomposition Make-Buy Decision Project Scheduling Task a task set Scheduling techniques 41