CS 551 Estimation

Fall 2005

1 December 2005

QSE Lambda Protocol

• Prospectus

• Measurable Operational Value

• Prototyping or Modeling

• sQFD

• Schedule, Staffing, Quality Estimates

• ICED-T

• Trade-off Analysis

Requirements Specification Spec

1. Project Title, Revision Number and Author2. Scope and Purpose of the system3. Measurable Operational Value4. Description5. Feature List including ICED T and Simplified QFD

analysis6. Interfaces7. Constraints8. Change Log and Expected Changes9. Responses to the unexpected10.Measurements11.Glossary12.References

Specification for Development Plan

• Project• Feature List• Development Process• Size Estimates• Staff Estimates• Schedule Estimates• Organization• Gantt Chart

Sizing Software Projects

• Effort = (productivity) (size)c

Staff

months

Lines of Code or

Function Points

500

Lines of Code

• LOC= Line of Code

• SLOC = Source Line of Code

• NCSLOC = New or Changed Source of Lines of Code

0

2

4

6

8

10

12

20 40 80 160 320 640 1280 2560 5120 10240 20480 40960

Function Points

Bell Laboratories data

Capers Jones data

Prod

uctiv

ity (F

unct

ion

poin

ts /

staf

f mon

th)

Productivity= f(Size)

Bernstein’s rule of thumb

• Productivity per staff-month:• 50 NCSLOC for OS code (or real-time system)• 250 NCSLOC for intermediary applications

(high risk, on-line)• 500 NCSLOC for normal applications (low risk,

on-line)• 10,000 NCSLOC for reused code

Reuse note: Sometimes, reusing code that does not provide the exact functionality needed can be achieved by reformatting input/output. This decreases performance but dramatically shortens development time.

Software Development Productivity for Industry Average Transaction Projects

Characteristic

Software Development Productivity (SLOC/WM)

Classical rates 130 - 195

Evolutionary approaches

244 - 325

New embedded flight software

17 – 105

Bernstein’s Trends in Software Expansion

Small ScaleReuse

1990SubsecTime Sharing

1995ObjectOrientedProgramming

1960MachineInstructions

1965MacroAssembler

1970High LevelLanguage

1975Database Manager

1980On-line

1985Prototyping

2000Large ScaleReuse

1

10

100

1000

3

15

3037.5

47

75 81113

142

475

638

RegressionTesting

4GL

Order of MagnitudeEvery Twenty Years

ExpansionFactor

TechnologyChange

Function Point Analysis

• Can use early in project (data from requirements)• Substantial data supports the methodology• Software Shop and Project characteristics are

accounted for in the Adjusted Function Points Technology and Project Methodology dependent

Technology changes negate history until the new relative improvement is established

• Still have to estimate other elements of the project• Could be done by converting UFPs to LOC for a specific

language (technology) and then using an algorithmic tool such as COCOMO or SLIM.

Adjusted Function Points

• Accounting for Physical System Characteristics

• Characteristic Rated by System User• 0-5 based on “degree of

influence”• 3 is average

UnadjustedFunction

Points (UFP)

UnadjustedFunction

Points (UFP)

General SystemCharacteristics

(GSC)

General SystemCharacteristics

(GSC)

X

=

AdjustedFunction

Points (AFP)

AdjustedFunction

Points (AFP)

AFP = UFP (0.65 + .01*GSC), note GSC = VAF= TDI

1. Data Communications

2. Distributed Data/Processing

3. Performance Objectives

4. Heavily Used Configuration

5. Transaction Rate

6. On-Line Data Entry

7. End-User Efficiency

8. On-Line Update

9. Complex Processing

10. Reusability

11. Conversion/Installation Ease

12. Operational Ease

13. Multiple Site Use

14. Facilitate Change

Computing Function Points

External Inputs – One updates two files

External Inputs (EI) - when data crosses the boundary from outside to inside.  This data may come from a data input screen or another application.

External Interface Table

                                 

For example, EIs that reference or update 2 File Types Referenced (FTR’s) and has 7 data elements would be assigned a ranking of average and associated rating of 4.

File Type References (FTR’s) are the sum of Internal Logical Files referenced or updated and External Interface Files referenced.

External Output from 2 Internal Files

External Outputs (EO) – when data passes across the boundary from inside to outside.  

External Inquiry drawing from 2 ILFs

External Inquiry (EQ) - an elementary process with both input and output components that result in data retrieval from one or more internal logical files and external interface files.  The input process does not update Internal Logical File, and there is no derived data.

EO and EQ Table mapped to Values

Computing Function Points

Internal Logical Files

Internal Logical Files (ILF’s) - a user identifiable group of logically related data that resides entirely within the applications boundary and is maintained through external inputs.

External Interface Files

• External Interface Files (EIF’s) - a user identifiable group of logically related data that is used for reference purposes only. The data resides entirely outside the application and is maintained by another application. The external interface file is an internal logical file for another application.

Proposed System

Proposed System

Check Status

Create Order

Shipment Notice

Inventory

Assign Inventory to Order

Inventory Assigned

New Inventory for Held Orders

Assign Order to Truck

Truckload Report

Shipping Invoices

Order Update

Order Display

Problem ResolutionDispatch

Accounting

Management Reports

Customer

Check Credit &

Completion

Users

Catalog

Orders

OrderCreation

Credit Check

InventoryAssignment

Held OrderProcessing

Completion

DispatchSupport

ProblemResolution

ManagementReporting

OA&M

Case Study: Web Front EndUse Cases Transactions Type Complexity UFP

End UsersLogon 1 I 3 3View Last Bill 1 Q 6 6Create Account 1 I 6 6View Current Services 1 Q 4 4Establish Analog CATV Service 1 I 6 6Add Data Service 1 I 6 6Add/Delete a Premium Channel 1 I 4 4Add/Delete a Digital Package 1 I 6 6View Trouble Status 1 Q 4 4View Order Status 1 Q 3 3View Information 5 Q 3 15

BackEndGet Account & Service Info 1 N 10 10Get Last Bill 1 N 10 10Create Account 1 N 10 10Create Order 1 N 10 10Account Validation 3 N 7 21Order Validation 3 N 7 21Get Trouble Status 1 N 7 7Get Order Status 1 N 7 7

ManagementView Customer Use Statistics 5 Q 4 20Troubleshoot Customer Scenario 5 Q 6 30

OA&MUser Administration 2 F 7 14Table Administration 15 F 7 105Usage DB Administration 1 F 15 15Temp DB Admin 1 F 15 15Schedule Reports 1 I 4 15Control Application 1 I 4 15Create Reports 1 I 6 15Application Alarms 1 O 7 15

Total Unadjusted Function Points 418

GSC Example: Web Front End

General System Characteristic Rating1 Data Communications 52 Distributed Data/Processing 43 Performance Objectives 54 Heavily Used Configuration 55 Transaction Rate 56 On-Line Data Entry 37 End-User Efficiency 58 On-Line Update 39 Complex Processing 3

10 Reusability 211 Conversion/Installation Ease 312 Operational Ease 413 Multiple Site Use 414 Facilitate Change 4

Total Degree of Influence 55

UFP (.65+.01*GSC)418 1.2

Adjusted Function Points 502

Software Costing

• Cost Development using FPA

• Estimate • Requirements

Engineering (1/3 of implementation

• Design (1/5 of implementation)

• Testing (1/4 of implementation

• Documentation & Training

FP per mo 5Dev Staff Mos 65.8Dev Staff Yrs 5.5Sys Eng 1.8Design 1.1Test 1.8Doc 1.0Trng 1.0Total 12.2

Staff Cost $150,000Project Cost $1,836,173

7.6

Function Points Evaluated

Advantages Disadvantages

Standards are established and reviewed frequently. Technology, platform, and language independent.

Largely a manual process primarily for transaction systems. Backfiring, FP derived from SLOC, is inaccurate and misleading.

Results are logical. Estimates are from the user’s perspective.

Accurate counting requires in-depth knowledge of standards and extensive training.

Estimates from requirements through full life-cycle.

Variations exist that are not standardized.

The COCOMO model

• Effort = a(NCSLOC/1000)b

• Embedded systems: a=3.6 b=1.2

• Semi-detached: a=3.0 b=1.12

• Application: a=2.4 b=1.05

COCOM II

• Effort = A(size)b П EM(i)• b = B + 0.01+∑SF(j); SF(j) are 5 scale

factors

• EM(i) : 17 cost drivers

See:

http://sunset.usc.edu/research/COCOMOII

Time

Staff-month

Ttheoretical

75% * Ttheoretical

Impossible design

Linear increase

Boehm: “A project can not be done in less than 75% of theoretical time”

Ttheoretical = 2.5 * 3√staff-month