Analysis and Design of Information Systems

436 Pages·2008·4.59 MB·English

Arthur M. Langer
Analysis and Design
of Information
Systems
Third Edition
ArthurM.Langer,EdD
FuFoundationSchoolofEngineering&AppliedScience
SchoolofContinuingEducation
GraduateSchoolofEducation
ColumbiaUniversity
NewYork,NY10027
USA
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Preface
Throughout the last 40 years the impact and importance of information
technology (IT) continues to transform the world. Indeed, we are very much
at the beginning stages of what I believe will be known as the technology
revolution—a revolution that will change every aspect of business and life in
general. While technology, both hardware and software, continues to evolve,
the one remaining constant is the challenge of understanding what the users of
applications really need, what they think they want, and what they will want as
their uses of systems mature.
Still, the process of mastering the analysis and design phase of the Software
DevelopmentLifeCycle(SDLC)continuestoperplexthemostsophisticatedIT
organizations and software development companies. And to make matters even
morecomplex,theITindustryhastransitionedtoaheavilyoutsourcedmodelof
softwaredevelopment,makingtherequirementsofwhatisnecessaryevenmore
important because of the risks of having applications developed abroad that do
not meet user expectations.
Perhaps the most significant development in applications has been the
Internet, with all the corresponding pieces: branding, Web development, and
interactive user interfaces have established many more substantial challenges
to how applications evolve. The most critical change, however, is the partici-
pation of a more sophisticated and unknown user: the consumer. The consumer
is a most unusual individual: he/she does not participate as part of an internal
organization, or external client, rather a transactional force that comes in and
out of the application with an enormous amount of uncertainty and constant
changeinbehaviorsandneeds.Furthermore,this“consumer”representsabroad
population, of culture, age, gender, and ethnicity differences.
With the significant challenges described above, it is imperative that we
expand analysis and design to provide developers from inside and outside the
business to clearly understand what is needed. Furthermore, applications need
to change more often, so that object-based design is no longer an alternative,
rather a necessity to allow organizations to continually evolve and mature their
abilities to serve their clientele. This book then focuses on providing direction
on the many alternatives to dealing with all types of systems, from large legacy
applications to on-line transactional systems that interface with a myriad of
internal and external systems.
Manyofthesefailuresofsystemsdevelopedhaveoccurredbecausetheyhave
notbeenbuiltonstrongfoundations.Inparticular,thereisalackofunderstanding
oftheengineeringprocessesthroughwhichapplicationsmustbebuilt.Thisbook
vi Preface
seeks to remedy this problem by focusing on the applied aspects of analysis to
create systems that meet the needs of their users, consumers, and businesses.
The analyst/designer encounters many obstacles on the road to designing appli-
cations.Manyoftheseobstacleshavenothingtodowithtechnicalchallengesat
all—they are problems that come from outside the realm of IT: politics, budget
and time constraints, and marketing pressures. All of these can challenge the
structured approach to analysis and design. This book addresses these obstacles
andrecommendswaystoovercomethem.Ihavealwayswarnedmystudentsby
tellingthem:“FollowtheYellowBrickRoad.”Thatis,startoutontherightpath
and you will end up in the place you want to be—in spite of all the obstacles
you may encounter on the way. I hope this book shows many IT professionals
thattheanalyst/designeristhemostimportantcomponentoftheSDLC.
This new edition aims to enhance the set of techniques and tools that the
analyst/designer requires for success. It also addresses some of the “softer” but
critical other skills such as creativity and the ability to understand the market
needs of the business. Furthermore, the successful analyst/designer must be
able to understand consumer needs; ensure integration with legacy systems;
provide user interface requirements; establish standards, security, and network
architecture; and finally to provide the necessary project management to ensure
implementation.
New to the Third Edition
Thisthirdeditionprovidesmoreexamplesandcasestudies;however,itcontains
two major upgrades from its predecessor: first, responding to feedback, I have
framed the modeling tools within an SDLC framework so that readers can have
a step-by-step understanding of when and how to use each of the modeling
toolsofanalysis.Toaccomplishthis,IprovideapopularSDLCapproachcalled
“the Barker Method” which was developed by Richard Barker from Oracle
Corporation. Second, the scope of analysis and design has been expanded to
include more specific information on Logic Data Modeling, specifically refer-
entialintegrity,namingconventions,logical-to-physicaldesignsteps,XML,data
values, and denormalization. I have also added new chapters on Web interface
tools, security and change control and data warehouse system design.
The Aim of This Book
The risks involved in performing analysis are significant: Those projects that
involve reengineering activities have a failure rate over 70 percent. With the
expansion of the Internet as a vehicle for electronic commerce, the stakes are
evenhigherthanbefore,andidentifyingthesourcesoffailurecanbeinvaluable.
In general, failures can be attributed to two kinds of risks: those associated
with the process of change and those relating to the technology itself. I am
Preface vii
confidentthatthesuccessratecanbedramaticallyimprovedifwefocuslesson
themethodologyandmoreontheabilityoftheanalysttoperformthework.This
book is therefore meant as a “practitioner’s guide” to doing analysis through
every facet of developing software solutions.
The book defines the word “analyst” to include any individual involved
in establishing the requirements and design of a system. For this reason, the
bookincludessubjectslikejointapplicationdevelopment(JAD)andprototyping,
which may not always be performed by analysts but which nevertheless fall
within the confines of the definition.
Myenthusiasmforwritingthisbookwassupportedbymanyofmystudents
who found that existing books on analysis are:
• verytheoretical.Althoughtheyexplainthemethodologies,theydonot
provide enough examples of their actual application.
• too procedural. They do not deal with the “human” aspects of devel-
oping requirements and thus do not provide a complete understanding
of how to be successful. After all, the whole point of analysis is to
servicehumanenterprises,notjusttocreatesystemsfortheirownsake.
The human side of analysis is as important as the technical side.
• lackingsimplebuteffectivecaseexamples.Theexamplesdonotdemon-
strate the concepts effectively or are too complex for practice study.
• too one-sided in their views. It is important to establish all available
methodologies,eventhosethatconflictwitheachother.Puttingopinions
into perspective and leaving many of the ultimate decisions to the
practitioner is a significant part of the analyst’s education.
The Intended Audience for This Book
Thisbookassumesareasonableunderstandingofcomputerconceptsandtermi-
nology. The material is presented to be used in a first-level analysis course
or university program. In addition, it can be used by practicing information
systems professionals or executives who are managing information technology
and need an in-depth understanding of the principles of the analysis and design
process,particularlyasitrelatestoWeb-baseddevelopment.Furthermore,many
programmers who are also performing analysis may find this book a way of
developing a useful approach to structured and object methodologies.
Acknowledgments
IwanttothankmycolleagueMelanieCaffreyforhercontributionstotheThird
Edition, namely, her expertise in both the System Development Life Cycle and
the Barker Model was extremely valuable. Ms. Caffrey also contributed her
exercises and case study used in our courses at Columbia University.
viii Preface
I also want to thank the students in the Service Learning in the Community
Environment (SLICE) at Columbia University’s Fu Foundation School of
Engineering and Applied Science (SEAS) for their feedback on the Second
Edition. This Third Edition will continue to be used to train underserved inner-
city adults in the hopes of building their careers as tomorrow’s analysts and
designers. Many thanks to Dr. Jack McGourty, the Associate Dean of Under-
graduate Students, for allowing us to implement the program at SEAS.
New City, New York, USA Arthur M. Langer
September 2007
Contents
Preface v
1. Introduction 1
What Is, Is................................................................................................. 1
Just What Is a Complex Project?............................................................. 3
The Tiers of Software Development........................................................ 6
User Interface............................................................................................ 6
Tools.......................................................................................................... 6
Productivity Through Automation............................................................ 7
Object Orientation..................................................................................... 7
Client/Server............................................................................................. 7
Internet/Intranet......................................................................................... 8
Problems and Exercises............................................................................ 9
2. System Development Life Cycle (SDLC) 10
System Development Life Cycle—Steps in Analysis
and Design............................................................................................ 10
The Barker Case Method.......................................................................... 15
3. The User Interface 21
Establishing User Interfaces..................................................................... 21
Forming an Interview Approach.............................................................. 21
Dealing with Political Factions................................................................ 24
Categories and Levels of Users................................................................ 25
Joint Application Development (JAD)..................................................... 28
Problems and Exercises............................................................................ 34
Mini-Project.............................................................................................. 35
Assignment................................................................................................ 35
4. Overview of Analysis Tools 36
The Concept of the Logical Equivalent................................................... 36
Tools of Structured Analysis.................................................................... 41
x Contents
Making Changes and Modifications......................................................... 41
Specification Formats............................................................................... 47
Problems and Exercises............................................................................ 50
5. Process-Based Tools 51
Data Flow Diagrams................................................................................. 51
Process Flow Diagrams............................................................................ 58
Data Dictionary......................................................................................... 63
SQL Data Types....................................................................................... 67
Process Specifications............................................................................... 70
State Transition Diagrams........................................................................ 77
Entity Relational Diagrams...................................................................... 81
Problems and Exercises............................................................................ 83
Mini-Project #1......................................................................................... 84
Assignment................................................................................................ 84
Mini-Project #2......................................................................................... 84
Assignment................................................................................................ 85
Mini-Project #3......................................................................................... 85
Assignment................................................................................................ 86
Mini-Project #4......................................................................................... 86
Assignment................................................................................................ 86
6. Logic Data Modeling Tools 87
Normalization Defined............................................................................. 87
Normalization Approaches....................................................................... 88
The Supertype/Subtype Model................................................................. 97
Combining User Views............................................................................ 101
Integration with Existing Models:
Linking Databases................................................................................105
Referential Integrity.................................................................................. 107
Database Naming Conventions................................................................ 108
View Naming Conventions...................................................................... 110
Field Length and Character Conventions................................................. 112
Null Values............................................................................................... 113
Denormalization........................................................................................ 114
Logic to Physical Databases..................................................................... 116
Data Types Usage and Conventions........................................................ 119
Business Rules.......................................................................................... 119
Triggering Operations............................................................................... 121
Problems and Exercises............................................................................ 122
Mini-Project #1......................................................................................... 122
Mini-Project #2......................................................................................... 123
Mini-Project #3......................................................................................... 124
Contents xi
7. Web User Interface Tools 127
Introduction............................................................................................... 127
Components of Web Design..................................................................... 128
Content...................................................................................................... 129
The Web Branding Process...................................................................... 130
Customer Service...................................................................................... 136
Text........................................................................................................... 139
Content Templates.................................................................................... 142
Navigation Placement............................................................................... 150
Site Architecture....................................................................................... 153
Non-Web-Based Interfaces....................................................................... 156
GUI and Styles of Manipulation.............................................................. 157
Advantages of GUI Systems.................................................................... 158
Disadvantages of GUI Systems................................................................ 159
Conclusion................................................................................................ 160
Where to Begin......................................................................................... 160
Database Design....................................................................................... 167
E-Commerce Application Requirements.................................................. 169
Problems and Exercises............................................................................ 174
8. XML in Analysis and Design 176
Introduction to XML................................................................................ 176
XML Structure.......................................................................................... 177
XML Parsing............................................................................................. 177
What XML Is Not..................................................................................... 178
Other XML Interfaces.............................................................................. 179
Document Object Model.......................................................................... 180
XML as a Common Data Format............................................................. 182
XML Applications with Database Systems............................................. 184
Analysis and Design of XML Documents............................................... 187
Step 1: Determining XML Documents.................................................... 188
Step 2: XML Data Schemas..................................................................... 193
Step 3: XML Reuse.................................................................................. 195
Storing XML Documents in a Database.................................................. 197
XML as a Centralized Data Search Engine............................................. 200
XML Query Usage................................................................................... 201
XML versus the Database........................................................................ 202
XML and SVG.......................................................................................... 203
9. Design Specification Tools 206
Business Specifications............................................................................. 206
Programming and Technical Specifications............................................. 210
xii Contents
Screen Specifications................................................................................ 212
Screens and Derived Elements................................................................. 213
Problems and Exercises............................................................................ 214
Mini-Project.............................................................................................. 218
10. CASE and Automated Techniques 229
CASE Defined.......................................................................................... 229
Why Does CASE Fail?............................................................................. 237
Why CASE Should Succeed.................................................................... 238
Open Systems Requirements and Client/Server...................................... 239
Problems and Exercises............................................................................ 242
11. Object-Oriented Techniques 243
What Is Object-Oriented Analysis?.......................................................... 243
Identifying Objects and Classes............................................................... 248
Object Modeling....................................................................................... 252
Relationship to Structured Analysis......................................................... 254
Problems and Exercises............................................................................ 259
12. Documentation and Acceptance-M Testing 260
Documentation.......................................................................................... 260
Acceptance Test Plans.............................................................................. 261
Quality During Analysis........................................................................... 261
How Much Can Be Tested?..................................................................... 261
Budget Process.......................................................................................... 264
Problems and Exercises............................................................................ 267
13. Business Process Reengineering 268
Analyzing Legacy Systems...................................................................... 269
Combining Structured and Object Techniques........................................ 270
Dealing with End Users............................................................................ 273
Information Systems Issues...................................................................... 274
System Development Life Cycle (SDLC)................................................ 276
Downsizing System Components............................................................. 277
Problems and Exercises............................................................................ 280
14. Security 281
Introduction............................................................................................... 281
Database Security and Change Control.................................................... 308
Version Control......................................................................................... 312