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Schedule and Effort. Planning Big Project: Waterfall-ish Style 1.Figure out what the project entails Requirements, architecture, design 2.Figure out dependencies.

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Presentation on theme: "Schedule and Effort. Planning Big Project: Waterfall-ish Style 1.Figure out what the project entails Requirements, architecture, design 2.Figure out dependencies."— Presentation transcript:

1 Schedule and Effort

2 Planning Big Project: Waterfall-ish Style 1.Figure out what the project entails Requirements, architecture, design 2.Figure out dependencies and priorities What has to be done in what order? 3.Figure out how much effort it will take 4.Plan, refine, plan, refine… 1

3 Example: Twitter Repression Report 2 Repressed citizen UC#1: Report repression UC#2: Clarify tweet Concerned public UC#3: View reports UC#3a: View on map UC#3b: View as RSS feed

4 One Possible Architecture 3 Twitter Façade Twitter Façade Geocoder Façade Geocoder Façade Database Apache+PHP Mapping Web site Google maps RSS Web service RSS Web service Tweet processor Tweet processor MySQL

5 Activity Graph: shows dependencies of project’s activities Filled circles for start and finish One circle for each milestone Labeled arrows indicate activities What activity must be performed to achieve a milestone? Dashed arrows indicate null activities 4

6 Activity Graph: shows dependencies of project’s activities 5 1a1a 1a1a 1c1c 1c1c 2 2 1b1b 1b1b 3a3a 3a3a 3b3b 3b3b 4 4 Do Twitter facade Do geocode facade Do tweet processor Do map output Test & debug map Test & debug RSS Advertise 3 3 Milestone 2: DB contains real data Milestone 3: DB contains real, reliable data Milestone 4: Ready for public use Test & debug components Design db

7 Effort Estimate for Activities Expert judgment Records of similar tasks Effort-estimation models Any combination of above 6

8 Expect to Refine Effort Estimations 7

9 Effort: Expert Judgment Not a terrible way to make estimates, but… Often vary widely Often wrong Can be improved through iteration and discussion How long to do the following tasks: Read tweets from Twitter via API? Send tweets to Twitter via API? Generate reports with Google maps? 8

10 Effort: Records of Similar Tasks Record the size of the component (lines of code) Breakdown # of lines added, reused, modified, deleted Record time taken Breakdown planning, design, implementing, testing, … Refer to this data when making future predictions aka Personal Software Process (PSP) Can also be done at a team level 9

11 Effort: Estimation Models Algorithmic (e.g., COCOMO) Inputs: description of team + project Outputs: estimate of effort required Machine learning (e.g., CBR) Gather descriptions of old projects + time taken Create a model (aka custom algorithm) (Same inputs / outputs as algorithmic estimation) 10

12 COCOMO-like Models 1.Assess the system’s complexity 2.Compute the number of application points 3.Assess the team’s productivity 4.Compute the effort 11

13 1. Assessing Complexity 12 e.g.: A screen for editing the database involves 6 database tables, and it has 4 views. This would be a “medium complexity screen”. This assessment calls for lots of judgment.

14 2. Computing Application Points (a.p.) 13 e.g.: A medium complexity screen costs 2 application points. 3GL component = reusable programmatic component that you create

15 3. Assessing Team Capabilities 14 e.g.: Productivity with low experience + nominal CASE… productivity = (7+13)/2 = 10 application points per person-month (assuming NO vacation or weekends!!!!!)

16 Typical CASE Tools Configuration management Data modeling Model transformation Program transformation Refactoring Source code generation UML 15 CASE: Computer Aided Software Engineering

17 Identify Screens, Reports, Components 16 Twitter Façade Twitter Façade Geocoder Façade Geocoder Façade Database Apache+PHP Mapping Web site Google maps RSS Web service RSS Web service Tweet processor Tweet processor MySQL 3GL components - Tweet processor - Twitter façade - Geocoder façade Reports - Mapping web site - RSS web service

18 Use Complexity to Compute Application Points 17 3GL components - Tweet processor - Twitter façade - Geocoder façade Reports - Mapping web site - RSS web service Simple model assumes that all 3GL components are 10 application points. Displays data from only a few database tables (3? 4?) Neither has multiple sections.  Each is probably a “simple” report, 2 application points. 2*2 = 4 a.p. 3*10 = 30 a.p = 34 a.p.

19 Assess the Team’s Productivity and Compute Effort E.g., Extensive experience with websites, XML No experience with Twitter or Geocoders Since 20 of 34 a.p. are on new stuff, assume very low experience (4) and no CASE maturity (4) Productivity = (4 + 4) / 2 = 4 a.p. / month So 34 a.p. would take 8.5 person-months Note: assumes no vacation or weekends 18

20 Distribute Person-months over Activity Graph 19 1a1a 1a1a 1c1c 1c1c 2 2 1b1b 1b1b 3a3a 3a3a 3b3b 3b3b Do Twitter façade (1.25) Do geocode façade (1.25) Design db (0.25) Do tweet processor (1.00) Do map output (0.25) Do RSS output (0.25) Test & debug map (0.25) Test & debug RSS (0.25) Advertise (1.0?) Test & debug components (3.75)

21 The Magic Behind Distributing Person-months Divide person-months between implementation and other activities (design, testing, debugging) Forgot to include an activity for testing and debugging components, revise activity graph Notice that some activities aren’t covered E.g., Advertising; either remove from diagram or use other methods of estimation 20

22 Do You Believe Those Numbers? Ways to get more accurate numbers: Revise numbers based on expert judgment or PSP Perform a “spike”: try something out, see how long it takes Use more sophisticated models to analyze how long components will really take User several models and compare Expect to revise estimates as progress proceeds 21

23 Further Analysis May Revise Estimates 22 1a1a 1a1a 1c1c 1c1c 2 2 1b1b 1b1b 3a3a 3a3a 3b3b 3b3b Do Twitter façade (1.50) Do geocode façade (0.75) Design db (0.25) Do tweet processor (0.50) Do map output (0.50) Do RSS output (0.25) Test & debug map (0.25) Test & debug RSS (0.25) 3 3 Test & debug components (4.25)

24 Critical Path: Longest Route Through Activity Graph Sort all the milestones in “topological order” i.e., Sort milestones in terms of dependencies For each milestone (in order), compute the earliest that the milestone can be reached from its immediate dependencies 23

25 Example: Computing Critical Path 24 1a1a 1a1a 1c1c 1c1c 2 2 1b1b 1b1b 3a3a 3a3a 3b3b 3b3b Do Twitter façade (1.50) Do geocode façade (0.75) Design db (0.25) Do tweet processor (0.50) Do map output (0.50) Do RSS output (0.25) Test & debug map (0.25) Test & debug RSS (0.25) 3 3 Test & debug components (4.25)

26 Example: Tightening the Critical Path 25 1a1a 1a1a 1c1c 1c1c 2 2 1b1b 1b1b 3a3a 3a3a 3b3b 3b3b Do Twitter façade (1.50) Do geocode façade (0.75) Design db (0.25) Do tweet processor (0.50) Do map output (0.50) Do RSS output (0.25) Test & debug map (0.25) Test & debug RSS (0.25) Test & debug components (4.25) What if we get started on the reports as soon as we have a (buggy) version of the database and components?

27 Slack Time Activity slack = latest possible start time – earliest possible Indicates how much “spare time” that activity has In case something goes wrong Activities on the critical path always have zero slack time 26

28 Example: Tightening the Critical Path 27 1a1a 1a1a 1c1c 1c1c 2 2 1b1b 1b1b 3a3a 3a3a 3b3b 3b3b Do Twitter façade (1.50) Do geocode façade (0.75) Slack = 0.75 Design db (0.25) Slack = 1.25 Do tweet processor (0.50) Do map output (0.50) Slack = 3.50 Do RSS output (0.25) Slack = 3.75 Test & debug map (0.25) Slack = 3.50 Test & debug RSS (0.25) Slack = Test & debug components (4.25) e.g.: If the finish is done at 6.25, then 3a cannot start later than The slack is then latest start – earliest = 6.00 – 2.50 = 3.50.

29 Gantt Chart Shows activities on a calendar Useful for visualizing ordering of tasks and slack Useful for deciding how many people to hire One bar per activity Line (or arrows) show dependencies between activities Milestones appear as diamonds 28

30 Example Gantt Chart 29 Gantt chart quickly reveals that we only need to hire two people (blue & green)

31 Next Steps Final Vision Statement DUE THIS FRIDAY!! (11/21) Midterm due 11/25 Homework #6 due 12/03 30


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