The Value Of Modeling

A technical discussion of software modeling
June 2004

The Value of Modeling

Gary Cernosek
IBM Rational Software Design and Construction Products
IBM Software Group
Eric Naiburg
IBM Rational Desktop Products
IBM Software Group

The Value of Modeling
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Contents
1

Executive summary

1

Introduction
1
2

3

Why model?
Why model software?

This white paperdiscusses how modeling can positively affect software and
systems development. The intended audience includes both technical and nontechnical personnel associated with the software development process.

What is modeling?

2

Executive summary

Why some developers choose not
to model software

4

When do I model?

7

How do I model?

8

What people are saying about the

Modelingcan be an effective way to manage the complexity of software
development. It enables communication, design and assessment of
requirements, architectures, software and systems. In spite of these virtues,
mainstream software development has yet to take advantage of modeling in
everyday practice.

value of modeling
9

Trends and the future

This white paper examines how modeling providesnot only visual but also
textual content, and why the combination is important. It also explains how to
model throughout the various phases of the software development life cycle and
what modeling types are appropriate for each phase. Although the focus will
be on modeling as a discipline in itself, the Unified Modeling Language (UML)
w ill be used as the common means for expressing themodels.
Introduction

This white paper discusses the value of modeling in the context of software
development. The concepts presented here are not new—savvy software
professionals have practiced modeling for years. But in the mainstream
software development community, only a fraction of software developers
formally model their software. This white paper examines the basics of what
motivates thepractice of modeling software. For those who are knowledgeable
of software modeling, those who know nothing about it or those who know of it
but have never embraced it, this white paper intends to explain the benefits and
values that this practice can offer.
What is modeling?
For many years, business analysts, engineers, scientists and other professionals
who build complex structures orsystems have been creating models of what
t hey build. Sometimes the models are physical, such as scaled mock-ups of
airplanes, houses or automobiles. Sometimes the models are less tangible, as
seen in business financials models, market trading simulations and electrical
circuit diagrams. In all cases, a model serves as an abstraction—an approximate
representation of the real item that is beingbuilt.

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Why model?
Why should you model something before you build it? Perhaps you should not.
Simple things do not necessarily need a model preceding its construction—such
as a simple checkbook register, a currency conversion utility, a doghouse or
a simple macro in a word processor that opens up a set of routinely used files.
Such projects share all ormost of the following characteristics:
• The problem domain is well known.
• The solution is relatively easy to construct.
• Very few people need to collaborate to build or use the solution (often only one).
• The solution requires minimal ongoing maintenance.
• The scope of future needs is unlikely to grow substantially.

But suppose none of these characteristics apply? Why do someprofessional
disciplines bother to create models? Why do they not just build the real thing
right away? The answer has to do with the complexity, the risk and the fact
that original practitioners are not always appropriate or even available for
completing the task.
Modeling provides architects and
others with the ability to visualize
entire systems, assess different
options and communicate...