PROBE

The PSP Size Estimating Approach

Q 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-1

PROBE - The PSP Size Estimating Approach r 1

Goals and Outline of Presentation

Goals An overview Proxy Based Estimating (PROBE) in the Personal Software Process (PSP) context

What they are & how PROBE works

Principles behind PROBE .

PROBE'S particular advantages

How PROBE fits in PSP

Outline

What is PSP - Context for PROBE

PROBE

Conclusions

Q 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-2

PROBE - The PSP Size Estimating Approach

I What is PSP - Context for PROBE I I Overview I

A process for individuals to use

Applies to structured personal tasks

Writing small programs or documents

Defining requirements or processes

Conducting reviews or tests, etc.

Introduced

In steps

With small software problems

Is a discipline for software engineering

Provides an effective foundation for large scale development practices

Q 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-3 v l .O - 0911 1/96

PROBE - The PSP Size Estimating Approach

What is PSP - Context for PROBE I PSPO Process Flow (Framework)

PSPO Process Flow

Requtrements

Q 1996 A. Winsor Brown BESIMSEE

Planning

Design

Code

Compile

Test

Postmortem

Fintshed Product

Time Defects

Plan Summary

PROBE-SE DOC-4

Project and Process Data Summary Report

I 1

PROBE - The PSP Size Estimating Approach - - -

What is PSP - Context for PROBE I PSPO.l Project Plan Summary

Student Program Instructor

Program Base(5)

Date Proaram # Language

Size (LOC)

Deleted (D)

Modified (M)

Added (A)

Reused (R)

Total New & Changed (N)

Total LOC m Total New Reused

Time in Phase (mh.) Planning Design Code Compile Test Postmortem

PIan

Total

PIan Actual To

Actual

Date

To Date To Date %

6 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-5

I

PROBE - The PSP size Estimating Approach

What is PSP - Context for PROBE PSPO.1 Project Plan Summary (cont.)

Defects Injected Planning

Design

Code

Compile

Test

Total Development

Defects Removed Planning

Design

Code

Compile

Test

Total Development

After Development

Actual To Date To Date %

Actual To Date To Date %

O 1996 A. Winsor Brown BESIMSEE PROBE-SE D O C 4

I , I

I

PROBE - The PSP Size Estimating Approach

What is PSP - Context for PROBE I PSPO.l Process Time Recording Log

Student Instructor

Date Program #

- --

Comments Date

O 1996 A. Winsor Brown BESIMSEE

Start Stop Interruption Time

Delta Time

Phase

PROBE - The PSP Size Estimating Approach I a h e t r v w s 1 I

Student Instructor

I n ; %king I 1 30 Build, r a c k g r 8Q Function

What is PSP - Context for PROBE I

Date

40 Assbnmnl W S w m 6O I n b d u e loo Envimnmnt

-

Program #

PSP Defect Recording Log

Date Number Type Remove Fix Time Fix Defect ID1 Description:

Date Number Type Remove Fix Time Fix Defect I c z z l l Description:

Date Number Type Inject Remove Fix Time Fix Defect I t I I I I [ I I E I Z l - Description:

(O 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-8

PROBE - The PSP Size Estimating Approach

I What is PSP - Context for PROBE I PSP Methods, Techniques and. Technologies

Cyclic development

Design Verification: Object state machines, Verifying program correctness Defining and evolving processes

1 Process benchmarking

Quality Code reviews Yield management Management Design reviews Defect removal and prevention strategies

Design Notations Correlation Operational scenarios Checklists for reviews Functional, State & Logic specifications Goal-Question-Metric Paradigm -

Personal PsPl .? Prediction Intervals Planning Size estimating Task planning Time and schedule estimating Process Test report Earned Value Tracking

PsPo.1 LOC Standard

Personal PSPO Coding standard Object and LOC Counters Current process Size measurement Defect Analysis

Process Time recording Process improvement Baseline Defect recording proposal (PIP)

Defect type standard I Linked Lists Statistics overview and standard deviation

Q 1996 A. Winsor Brown BESIMSEE PROBE-SE.DOC-10

PROBE - The PSP Size Estimating Approach

What is PSP - Context for PROBE I I

PSP Size Estimating Approaches Discussed

Fuzzy logic

Divide historical product size data into size ranges and characteristics

Compare the planned product with these prior products

Based on this comparison, select the size that seems most appropriate for the new product

Function points

Standard Components

Delphi

63 1996 A. Winsor Brown BESIMSEE

PROBE - The PSP Size Estimating Approach

What is PSP - Context for PROBE I PSP Size Estimating Approaches Discussed (cont.)

Standard Components

Historical Data

- Establish the principal product size levels (components, modules, screens, etc.)

- Determine typical sizes of each level

New Product

- Determine the component level at which estimation is practical

- Estimate how many of those components will likely be in the product

- Determine the maximum and minimum numbers possible

- Calcuate the maximum, minimum and likely sizes as total of

o number of components of each type

o times typical sizes of each type

- Calculate size = (maximum + 4*likely + minimum)/6

(D 1996 A. Winsor Brown BESIMSEE PROBE-:;k DOC-12

PROBE - The PSP Size Estimating Approach

What is PSP - Context for PROBE I PSP Size Estimating Approaches Discussed (cont.)

Delphi

Uses several estimators

- each makes an independent estimate

- each submits estimate to a coordinator

Coordinator

- calculates average estimate

- enters on form: average, other estimates (anonymously), and previous estimate

When reestimates stabilizes

- average is the estimate

- range is range of original estimates

(O 1996 A. Winsor Brown BESIMSEE PROBE-SE D O G 1 3

PROBE - The PSP Size Estimating Approach

PROBE - The PSP Size Estimating Approach Outline

What is PSP - Context for PROBE

Conclusions

O 1996 A. Winsor Brown BESIMSEE

PROBE - The PSP Size Estimating Approach -

PROBE Process Details PROxv Based Estimates - Proxies

Basic issues Good size measures are detailed

Early estimators can rarely think in detail

Alternatives

Delay estimate until detail available

Make best guess - use Fuzzy Logic? Standard Components? Delphi?

identify a suitable proxy

Good proxies

Correlate closely to development costs

Are easy to visualize early in development

Should be physical entity that can be counted

Example Proxies

Function points

Objects

Product elements (components; screens, reports, scripts, files; chapters)

O 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-1 5 v l . 0 - 09/11/96

PROBE - The PSP Size Estimating Approach

PROBE Process Details PROxv Based Estimates - Obiects as Proxies

Correlation with development hours

Numbers of objects correlate reasonably well

Object lines of code (LOC) correlate very closely

Object LOC: estimated using the standard component estimating method

Total LOC: estimated from historical relationship Object - L0C::Total - LOC

Objects (as application entities) - can be visualized early in development [Functions and procedures can often be estimated the same way]

Counting can be automated for

Objects, and their LOC

Functions and procedures, and their LOC

What's Needed

t Object and LOC counter(s)

Historical data for standard component object LOC

Historical relationship of Object - LOC to Program - LOC

0 Rules for when to apply

O 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-16

PROBE - The PSP Size Estimating Approach - - -

PROBE Process Details Historical Data

LOC & LOC per Object Counters

Personal Coding and Line of Code counting standards: developed as Report Exercises 1 & 2 in PSP course

LOC and LOC per Object counters: developed as Programming Exercises 2 & 3

LOC and LOC per Object results for Programming Exercises 1 ..3: called for as "test results" from Proramming Exercise 3

Historical data for standard component object LOC

Program Number 1A

2A

Historical relationship of Estimated Object LOC to Actual Program LOC: Linear Regression Parameters calculated by Programming Ex.

Q 1996 A. Winsor Brown BESIMSEE PROBE-SE.00C-17 v l .O - 0911 1196

Object Name ABC DEF GHI

. . .

Number of Methods 3 2 4

Object LOC 86 8 92

Total Program LOC

212

I

PROBE - The PSP Size Estimating Approach

PROBE Process Details PSPO.1 Postmortem Process - Size Data

I I ... -- .. .- ...... .- ..-....... .- . PSPol PsPol watts* /

j 8 Real~st~c PSPO1-Planning PSPO1 -Development PSPO1-Postmortem Postmortem I Size-data only /

i v0.2 9 / 1 m 1 i <PPOlWPsS bdez i

PSPO.1 Project

Summary

? .- .i .............................. p,p ...................................

PSPO1-Postmortem

1-Defects-Injected Complete-PIP: Complete

PIP forms describing process problems.

improvement suggestions. and lessons learned.

2- Defects-Removed 4-Actual-Time

I

Counter

Project Exerc~se Source

(PESC)

Time Recording

(TRL)

completed

Determine-LOC: Determine the base.

reused, deleted. modified. added.

total. total new and changed. and

new reused LOC

I 1 Enter- Data. I ~nterthese data on the

R e v R L Enter-t1me-per-phase-on~P01 PPS Rev~ew the I 4 completed Time

Enter the total time spent m each PSPOl phase under Actual on the

I . /I ~ e c o r d i n ~ Log I! ~ro j&t Plan Summary form.

Q 1996 A. Winsor Brown BES/MSEE PROBE-SE DOC-18

PROBE - The PSP Size Estimating Approach

PROBE Process Details Size Estimating Overview

Product requirement

Obtain historical data

1

I Produce conceptual design I

Subdivide the product into parts 1

Do the parts resemble parts in the database?

Yes

I Select the databa

I most like new ones I

Repeat until the product parts are

the right size

Estimate the new Repeat for part's relative size all parts

Sum the estimated sizes of the new parts

I

I Estimate the total product size I Size Estimate

Q 1996 A. Winsor Brown BESIMSEE

+ PROBE-SE DOC-19

PROBE - The PSP Size istimating Approach

PROBE Process Details PSP Size Estimating Template

Student Instructor

Date Program #

BASE PROGRAM BASE SIZ E(B) => => => => => => => => => => LOC DELETED(D) => =>' => => => => => => => LOC MODlFlED(M) => => => => => =>, => => =>

PROJECTED LOC BASE ADDITIONS: TYPE METHODS REL. SIZE LOC

TOTAL BASE ADDITIONS (BA) => => => => => =>

NEW OBJECTS: TYPE^ METHODS REL. SIZE LOC (NewReuse*)

TOTALNEWOBJECTS (NO) => => => => => => =>

O 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-20

i ! r

PROBE - The PSP Size Estimatina Approach U~ - .

PROBE Process Details PSP Size Estimating Template (cont.)

LOC

REUSEDTOTAL(R) => => => => => => => => => Projected LOC: P = BA+NO Regression Parameter: Po Regression Parameter: PI Estimated Estimated Estimated Prediction

Newand Changed LOC: N = po + p,*(P+M) Total LOC: T = N + B - D - M + R Total New Reused (sum of * LOC): Range: Range

Upper Prediction Interval: Lower Prediction Interval: Prediction Interval Percent:

UP1 = N + Range LPI = N - Range

Q 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-21

PROBE - The PSP Size Estimating Approach

PROBE Process Details I Estimating Method

Start

Design

I . Identify Objects

Number of Object Methods Type

Relative Reuse Size Categories

Calculate Added and Modified LOC

Q 1996 A. Winsor Brown BESIMSEE

Estimate Program Size

I Calculate Prediction Interval

PROBE - The PSP Size Estimating Approach .- PROBE Process Details

I Process and Statistical Refinements

Historical data on object LOCs

Highly variable

- language & design style influences

- helps to normalize by number of methods

Divided into basic types: logic, control, 110, files, display, data, text, calculation, set-up, error handling

Size range for object types based on log-normal distribution

Prediction Intervals - Reality check

70% and 90% likely range around the estimate

Calculated from same data used to calculate the regression factors

Uses the student-t

63 1996 A. Winsor Brown BESIMSEE

PROBE - The PSP Size Estimating Approach

Outline

What is PSP - Context for PROBE

PROBE

Conclusions e

Q 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-24

PROBE - The PSP Size Estimating Approach

PROBE Process Details I PSPl Framework

Planning

I Customer I

I

I I I I I

Produce the I I

conceptual design. I I I

PSP 1 . 1 PROBE 8 Planning Framework

0 Items

C] Tasks

I I I I I

Estimate the product size. (Chapter 5 )

I I I I I

Estimate the I I

resources. (Chapter 6)

I I I I I I

Produce the schedule.

(Chapter 6)

I

Management

I t- I

I

I Develop the I I Analyze the

product I I schedule data process. I I I I I I

I I

63 1996 A. Winsor Brown BESIMSEE vl .O - 0911 1/96

PROBE - The PSP Size Estimating Approach

Conclusions Actual Results - Estimating Error

UNISYS PSP Class

Actual Size Range

- Program Number

WCU PSP OC2

Actual Size Range

1 2 3 4 5 6 7 8 9 1 0 1 - - - - - Min I - Program Number

Q 1996 A. Winsor Brown BESIMSEE

UNISYS PSP Class

Size Estimating Error Range

1 2 3 4 5 6 7 8 9 1 0

Program Number

I ---- M a x

I- Clas:

wcu PSP o c 2

Size Estimating Error Range

200 .

Program Number

150

100

50

r -50 ..

-100 -

/'\ .. / \

/ \ - .. , \

-1' Clas:

0 . e - -. _ . - .___- - . .

1 2 3 4 5 6 7 8 9 1 0

I Conclusions I

Teachable

Practical

Actual results indicate: Improvement over time

Improvable?: regression based on % error rather than absolute error

63 1996 A. Winsor Brown BESIMSEE PROBE-SE DOC-27