MIS 495 -- Dr. Reithel
Chapter 5

Software Scope-- Software scope describes function, performance, constraints, interfaces, and reliability. Determining software scope is the first activity in software project planning. Function and performance allocated to software during system engineering should be assessed to establish a project scope that is unambiguous and understandable at management and technical levels.

Resources-- The second task of software planning is estimation of resources required to accomplish the software development effort. The development resources can be viewed as a pyramid, with People at the top, Reusable Software Components in the middle, and Hardware/Software Tools at the base.

Reusability-- The creation and reuse of software building blocks. There are four software resource categories that should be considered as planning proceeds:

Software Sizing

In the context of project planning, size refers to a quantifiable outcome of the software project. Size can be measured in LOC (lines of code) when using the direct approach, and by FP when using an indirect approach. Putnam and Myers suggest four approaches to the sizing problem:

Process-Based Estimation

This method, the most common technique for estimating a project, bases its estimate on the process that will be used. The process is decomposed into a relatively small set of activities or tasks and the effort required to accomplish each task is estimated. Problem functions and process activities are melded, then the planner estimates the effort that will be required to accomplish each software process activity for each software function. Finally, costs and effort for each function and software process activity are computed.

The COCOMO Model (also, see page 121 of the Pressman textbook)

The COnstructive COst MOdel, or COCOMO, is a hierarchy of software estimation models. The Basic COCOMO model computes software development effort (and cost) as a function of program size expressed in estimated lines of code. The Basic COCOMO equations follow: E=ab(KLOC)raised to the bb power and D=cb(E)raised to the db power. Where E is the effort applied in person-months, D is the development time in chronological months, and KLOC is the estimated number of delivered lines of code (in thousands). The remaining coefficients are listed in the table below.

Software Project ab bb cb db
organic 2.4 1.05 2.5 0.38
semi-detached 3.0 1.12 2.5 0.35
embedded 3.6 1.20 2.5 0.32

The Intermediate COCOMO model computes the software development effort as a function of program size and a set of "cost drivers" that include subjective assessments of product, hardware, personnel, and project attributes. This model takes the form: E=ai(KLOC)raised to the bi power x EAF, where E is the effort applied in person-months and EAF is the effort adjustment factor. The coefficients are given in the following table:

Software Project ai bi
organic 3.2 1.05
semi-detatched 3.0 1.12
embedded 2.8 1.20

The Make-Buy Decision

Sometimes it is more cost effective to acquire, rather than develop, computer software. This make-buy decision may be complicated by a number of options, such as: purchasing software off the shelf, buying and modifying components to meet specific needs, and custom-building software by an outside contractor.

Guidelines for make-buy decision

Outsourcing-- simply contracting software engineering activities to a third party, who does the work at lower cost.

Outsourcing Tips and Resources

Some of the more popular outsourcing companies today

Suggested Links for Further Readings
Updated version of the COCOMO model
Glossary of project management terms
Listing of project management resources
Detailed paper and references for project cost analysis
List of WWW references for software project estimation

Last Modified: Friday, 30-Jan-98 9:45:00 CDT
Copyright © 1997 University of Mississippi. All rights reserved.

Comments: reithel@bus.olemiss.edu