An Improved Approach to Project Estimation Based on Software Artifact Reuse by David T. Henrickson

Overview Introduction What is Reuse Approaches to Project Estimation A comparison of Domain Engineering and Artifact Repository Levels of Reuse to be Considered Adapting an Artifact –Tracking Tool for Reuse of Project Costs Summary

Introduction Project estimation fast and accurate Development artifacts Traceability Artifact repository

Reuse Opportunities Potential –the set of reuse opportunities that will result in actual reuse when exploited Targeted –the set of reuse opportunities toward which an organization directs its effort Actual –the set of reuse opportunities exploited

Reuse Capability Model Measures reuse efficiency and proficiency Reuse Opportunity Potential Reuse Opportunity Targeted Reuse Opportunity Actual Reuse Opportunity

Reuse Capability Reuse Proficiency R PROFICIENCY = R A / R P Reuse Efficiency R EFFICIENCY = R A / R T Reuse Effectiveness R EFFECTIVENESS = N(C NR – C R ) / C D N = Number of systems C NR = Cost of developing without reuse C R = Cost of utilizing reuse C D = Cost of Domain engineering © Davis [1993]

Potential Opportunities Target Opportunities Actual Opportunities Low Reuse Capability © Davis [1993] reuse efficiency = 0.10 reuse proficiency = 0.08

Potential Opportunities Target Opportunities Actual Opportunities High Reuse Capability © Davis [1993] reuse efficiency = 0.95 reuse proficiency = 0.65

What is Reuse? The use of existing software in the development of new software –Lim[1998]

Artifact Reuse Requirement Specification System Models Architecture Source Code Use-case Scenarios Test Scenarios

Basic Concepts of Reuse In order to reuse software there must be software to reuse –Tracz[1995] Consumer –person who actually reuses the software Producer –person who initially produces the software being reused

Corporation Consumer Producer Some examples of reuse organizations © Wiles [1999]

RARE IDIOM RARE – Reuse Assisted Requirements Elicitation IDIOM – Informal Document Interpreter Organizer and Manager

RARE IDIOM Highly complex tool to identify reuse opportunities Uses Bayesian weights based on keywords also called facets

Premise Similar requirements produce similar artifacts If an artifact has already been produced, we know what its value is

Approaches to Project Estimation Top-Down (FPA) –Underestimates costs Bottom-up (COCOMO II) –Overestimates costs Artifact Repository –Reuse must become a way of life –Repository must be built

Artifact Repository Approach File records key on requirement Decide which artifacts to reuse Decide how many are unique –Develop for reuse Estimate Tailoring costs Total: # of assets  [ value associated with each asset ] + tailoring costs a=1

Domain Engineering Identify and document commonalities across products in a particular domain Creating reusable and modifiable domain models

Artifact Repository Identify and document common requirements and their artifacts Attach a value to each artifact for project estimation Reuse artifacts as products of requirements regardless of domain

Project A Word Processor Project B Spread Sheet Project C Data Base System Project D Financial Planner Project E Internet Search Engine New Project Being Considered will need to: Create invoices Store data Create forms (paper) Create Reports Transfer data on a network

Requirement Code Graphic User Interface Hardware Control Number Each entity in the set includes a dollar value. In this way if we only use some of the artifacts we only charge for what we use.

Levels of Reuse Requirement Specification System Models Architecture Source Code Use-case Scenarios Test Scenarios

User Requirements User Natural Language Imprecise Non-Technical Application Terminology Specification Software Engineer Formal Language Precise Technical Software Terminology versus Requirements vs. Specification Dichotomy © Cybulski [1995]

Summary Introduction What is Reuse Approaches to Project Estimation A comparison of Domain Engineering and Artifact Repository Levels of Reuse to be Considered Adapting an Artifact –Tracking Tool for Reuse of Project Costs Summary