In the seminars, presentations, and classes we teach on data warehousing, we are often subjected to what appear to be "impossible situations." Likewise, in the DM Review "Ask the Experts" forum (http://www.dmreview.com) we are confronted with questions that, at first glance, appear to have no answers or solutions. However, they do have solutions, and that's what this book is all about.

We took the 91 impossible situations discussed in this book from our classes, from the DM Review "Ask the Experts" forum, from data warehouse consultants, and from colleagues in the field who have experienced these situations. These are all real situations, but we have disguised them to protect the authors as well as to protect the organizations experiencing the situations from the attendant shame and humiliation. As a side note, reviewers of specific situations in our manuscript were quick to say, "I know what company this describes," and they were almost always wrong.

The Purpose of This Book

There is no reason that each organization, as it begins and continues to develop data warehouse projects, must wrestle with many of the very difficult situations that have confounded other organizations. The same impossible situations continue to raise their ugly heads, often with surprisingly little relation to the industry, the size of the organization, or the organizational structure. In this book we let you know you are not alone and your problems are not unique. We also offer hope to the perplexed who see no obvious solutions to their problems.

Some of the situations should resonate with those of you planning to enhance your data warehouse by adding new data, additional users, or new applications. It may be that the impossible situation has not yet emerged, but you definitely see it just around the bend. After reading this book, you should be able to avoid the situation rather than needing to fix it after it has developed.

Who Should Read This Book

Every stakeholder, data warehouse architect, data warehouse project manager, and user liaison responsible for any portion of a data warehouse faces the challenges identified in these pages. These people are looking for solutions to situations that, at first, appear to have no possible answer.

This book does not present an introduction to data warehousing. To benefit most from this book, you should have some level of familiarity with data warehousing through practical experience, conferences, or previous reading of data warehouse texts. This book is also not geared to any primary topic such as meta data or data quality; instead, it covers a broad range of areas. The reference section lists both introductory and more advanced suggested reading material.

User liaisons and managers may wish to read only Part I (Impossible Management Situations). All others will want to read both Part I and Part II (Impossible Technical Situations).

How This Book Is Organized

As mentioned, the first part of the book deals with managerial situations and the second part with technical situations. The order within these sections is very roughly the order in which projects are developed and situations are encountered, but each chapter stands alone without depending on those that precede it. You can read the book from front to back, but more likely you will be drawn to the chapters describing the problems that cause you the most pain. For example, if you struggle with data quality issues, Chapter 11, Data Quality, is the place to start. Each subsection of a chapter presents a different impossible situation related to the chapter's topic, followed by the experts' suggested solutions (presented in the alphabetical order of the experts' last names).

The Data Warehouse Glossary at the back of the book clarifies some terms and helps keep you from going down the wrong path. Misunderstanding the terminology used in this fast-changing field has caused significant misinterpretation that has resulted in wasted time and money, dissension, and hurt feelings. The Data Warehouse Glossary contains acronyms as well as data warehouse and information technology terms. A few of these have more than one definition. Please refer to the definitions to avoid any misunderstandings as you read through the situations and solutions. If your native language is not English, you will find the Colloquialism Glossary useful since the experts used many colloquial expressions in their contributions to this book.

You will notice strong biases in the experts' responses. The experts came to these dearly held opinions honestly through extensive experience in real-world situations. A few of the answers are embarrassingly similar, while some sharply disagree, appearing to contradict each other. Recognizing that there is usually more than one answer to every problem, very much depending on the organization and the situation, we made no attempt to reconcile the differences. We trust you will astutely choose the solution that will work best in your organization.

The Experts Who Wrote This Book

The following people contributed their expertise to address the situations we present in this book:

• Sid Adelman
• Joyce Bischoff
• Jill Dyche
• Douglas Hackney
• Sean Ivoghli
• Chuck Kelley
• David Marco
• Larissa Moss
• Clay Rehm

True experts, these men and women have worked in the data warehouse arena for a cumulative 142 years. If anyone can address these impossible situations, they can.

The experts suggested best practices based on their experiences with both successful and unsuccessful implementations. The experts correctly identified many of the situations as reflecting the symptoms of a dysfunctional organization, knowing that without understanding the real causes, no effective solution could be honestly recommended. When presented with insufficient information, the experts resorted to making assumptions about the situations.

The experts' bios appear in the back of the book.

How to Contribute New Impossible Situations

A number of impossible situations came to our attention after the experts received the original batch of 91 situations, and we all feel sure more will appear. If you want to contribute a new situation for consideration, please send it to impossibles@sidadelman.com . We may include your situation in a second edition of this book.

Acknowledgments

The situations in this book were gleaned from a variety of sources. A major source was my Data Warehouse Project Management Seminar, in which students would present seemingly impossible situations. I'd like to thank all the students in this seminar who were brave enough to expose their extremely difficult if not impossible situations.

My clients, my colleagues, and the experts represented in this book contributed many of the other situations. There are no attributions for the impossible situations themselves. This was intentional to protect the reputations and careers of those who submitted them.

A number of situations were pulled from submissions to DM Review's "Ask the Experts" forum, mentioned earlier. My thanks to the publishers of DM Review who allowed us to use those submissions and to Mary Jo Nott, the Web Editor at DM Review who manages the forum.

This book is a compilation of hard-won wisdom from the experts—my colleagues I've been privileged to know and work with. As you will see in their solutions, there would not have been a book without their insightful contributions. Thanks especially to Larissa Moss and Joyce Bischoff for their excellent ideas and suggestions that went well beyond their expert solutions.

Thanks also go to the original reviewers who made excellent suggestions a

Sid Adelman is founder of Sid Adelman & Associates, an organization specializing in planning and implementing data warehouses. He presents regularly at data warehouse conferences and conducts a Data Warehouse Project Management seminar. Sid is also a founding member of the BIAlliance. He jointly developed a methodology that provides a master plan for implementing data warehouses. He wrote Data Warehouse Project Management (Addison-Wesley, 2000) with Larissa Moss.

Joyce Bischoff, president of Bischoff Consulting, Inc., is an internationally recognized consultant, writer, and lecturer specializing in all aspects of data warehousing, database design, and design methodologies. She has been involved in planning, designing, implementing, and performing design reviews of data warehouses in more than 50 companies in the credit card, chemical, pharmaceutical, insurance, financial, oil refining, publishing, and hospital industries. She is the lead author of the book Data Warehouse: Practical Advice from the Experts 1997, which brings together opinions from 20 contributing authors, and a member of the expert panel for the monthly column "Ask the Experts" at http://www.dmreview.com. She is the author of numerous articles and frequently presents at data warehousing conferences all over the world. She may be reached at JoyceBischoff@cs.com.

Jill Dyché is a partner with Baseline Consulting Group, a specialty consulting firm focusing on the delivery of business intelligence solutions across industries. Since 1985 she has been working with Fortune 1000 companies worldwide to help align strategic technology initiatives with corporate business objectives. Jill is a frequent speaker at technology and marketing conferences, and her articles have been featured in a variety of publications: Information Week, Oracle magazine, Teradata Review, Telephony Magazine, The Washington Times, and The Chicago Tribune.

Douglas Hackney is President of Enterprise Group, Ltd. and is a monthly columnist for Data Management Review. He has contributed to Computer World and speaks regularly at industry events, including DCI's Data Warehousing Conference, Bill Inmon's Data Warehousing Conference, and the Data Warehouse Institute.

Sean Ivoghli is the founder and president of Digital Symmetry, Inc., formerly the Data Warehouse Consulting Group, a consulting firm that specializes in providing end-to-end data warehousing, business intelligence, and data/application integration solutions. He has over 12 years of experience in full life-cycle data warehouse and information systems development, and he provides expert consulting services in data warehouse design, development, project management, and information management strategies. Mr. Ivoghli is the coauthor of Compass, a comprehensive data warehousing methodology that offers multiple tracks for developing scalable, flexible, and high-performance data warehousing and data mart solutions in a cost-effective manner. He can be reached at sivoghli@digitalsymmetryinc.com and at sivoghli@dwcg.com.

Chuck Kelley is an internationally known expert in database technology. He has over 25 years of experience in designing and implementing operational/production systems and data warehouses. Mr. Kelley has worked in some facet of the implementation process of over 45 data warehouses. Mr. Kelley teaches seminars on SQL, Database Internals, Implementing the Data Warehouse, Designing and Implementing the Star Schema from Your Operational System, and other database and data warehousing topics. He has been a speaker at Database World, Client/Server World, UniForum, COMDEX, Rdb Conference, DECUS Symposia, and many data warehouse conferences. He coauthored a book with W. H. Inmon 1994 on data warehouses and is a member of the panel on the "Ask the Experts" column at http://www.dmreview.com. Mr. Kelley has been published in many trade magazines on database technology, data warehousing, and enterprise data strategies. He can be reached at chuck.kelley@excellenceindata.com or at his Web site at http://www.excellenceindata.com.

David Marco is an internationally recognized expert in the fields of data warehousing, e-business, XML, and business intelligence, and he is the world's foremost authority on meta data. He authored the book Building and Managing the Meta Data Repository 2000b. Mr. Marco also serves as the editor of Real-World Decision Support, an electronic newsletter focusing on business intelligence and e-business topics (http://www.EWSolutions.com/newsletter.asp). Mr. Marco has published over 80 articles and is a columnist for Application Development Trends, Database Trends, and DM Review magazines. Mr. Marco has been selected as a judge for the 1998-2002 DM Review World-Class Solutions, 2002 TDWI Pioneering Solutions, and 1999-2002 Microsoft Industry Solutions awards. In addition, Mr. Marco was a finalist for the 2000 DAMA Individual IT Achievement award.

Mr. Marco has presented over 70 keynote addresses and courses at all the major data warehousing and meta data repository conferences throughout the world. He also cosponsors with Pennsylvania State University a certified series of courses on data warehousing and business intelligence, and he teaches data warehousing at the University of Chicago. Mr. Marco is the founder and President of the Chicago-headquartered Enterprise Warehousing Solutions, Inc. (EWS), a strategic partner and systems integrator dedicated to providing clients with best-in-class business intelligence solutions using data warehousing and meta data repository technologies. EWS provides strategic consulting services and full life-cycle implementation services for Global 2000 corporations and government institutions and has been awarded a government GSA Schedule. In addition, EWS presents the Marco Master's Series, which is the industry's first and only certified meta data training course. Visit http://www.EWSolutions.com for more information about EWS and the Marco Master's Series. Mr. Marco may be reached at DMarco@EWSolutions.com.

Larissa Moss is founder and president of Method Focus, Inc., a consulting firm specializing in business intelligence and data warehousing. She is a frequent lecturer and speaker at conferences in the United States, Europe, and Asia on data warehousing, project management, development methodologies, and organizational and cultural issues. Her articles on these topics are regularly published in magazines such as DM Review and Journal of Data Warehousing. She is coauthor of Data Warehouse Project Management (Addison-Wesley, 2000) and Impossible Data Warehouse Situations (Addison-Wesley, 2003). She is a senior consultant at the Cutter Consortium and one of the authors of their Business Intelligence Executive Reports.

Clay Rehm, CCP, PMP, is president of Rehm Technology (http://www.rehmtech.com), a consulting firm specializing in data integration solutions. He provides hands-on expertise in project leadership and management, assessments, methodologies, data modeling, database design, meta data and systems analysis, design, and development. He has worked in multiple platforms, and his experience spans operational and data warehouse environments. He is a technical book editor and author, instructor, and speaker. He serves on the panel of the DM Review "Ask the Experts" Web site (http://www.dmreview.com) and on the Carroll College Business Advisory Council.

With a passion for data architecture, he is well versed in DB2, SQL Server, and Access. He is Access 2000 Microsoft Office User Specialist (MOUS) Certified, a Certified Computing Professional (CCP), and a certified Project Management Professional (PMP). He holds a bachelor's of science degree in computer science from Carroll College and is currently working on his master's degree in software engineering.

He is a member of the Data Management Association (DAMA), the Professional Society of SQL Server (PASS), and the Project Management Institute (PMI). He can be reached at clay.rehm@rehmtech.com.

0201760339AB09262002

In the seminars, presentations, and classes we teach on data warehousing, we are often subjected to what appear to be "impossible situations." Likewise, in the DM Review "Ask the Experts" forum (http://www.dmreview.com) we are confronted with questions that, at first glance, appear to have no answers or solutions. However, they do have solutions, and that's what this book is all about. We took the 91 impossible situations discussed in this book from our classes, from the DM Review "Ask the Experts" forum, from data warehouse consultants, and from colleagues in the field who have experienced these situations. These are all real situations, but we have disguised them to protect the authors as well as to protect the organizations experiencing the situations from the attendant shame and humiliation. As a side note, reviewers of specific situations in our manuscript were quick to say, "I know what company this describes," and they were almost always wrong. The Purpose of This Book There is no reason that each organization, as it begins and continues to develop data warehouse projects, must wrestle with many of the very difficult situations that have confounded other organizations. The same impossible situations continue to raise their ugly heads, often with surprisingly little relation to the industry, the size of the organization, or the organizational structure. In this book we let you know you are not alone and your problems are not unique. We also offer hope to the perplexed who see no obvious solutions to their problems. Some of the situations should resonate with those of you planning to enhance your data warehouse by adding new data, additional users, or new applications. It may be that the impossible situation has not yet emerged, but you definitely see it just around the bend. After reading this book, you should be able to avoid the situation rather than needing to fix it after it has developed. Who Should Read This Book Every stakeholder, data warehouse architect, data warehouse project manager, and user liaison responsible for any portion of a data warehouse faces the challenges identified in these pages. These people are looking for solutions to situations that, at first, appear to have no possible answer. This book does not present an introduction to data warehousing. To benefit most from this book, you should have some level of familiarity with data warehousing through practical experience, conferences, or previous reading of data warehouse texts. This book is also not geared to any primary topic such as meta data or data quality; instead, it covers a broad range of areas. The reference section lists both introductory and more advanced suggested reading material. User liaisons and managers may wish to read only Part I (Impossible Management Situations). All others will want to read both Part I and Part II (Impossible Technical Situations). How This Book Is Organized As mentioned, the first part of the book deals with managerial situations and the second part with technical situations. The order within these sections is very roughly the order in which projects are developed and situations are encountered, but each chapter stands alone without depending on those that precede it. You can read the book from front to back, but more likely you will be drawn to the chapters describing the problems that cause you the most pain. For example, if you struggle with data quality issues, Chapter 11, Data Quality, is the place to start. Each subsection of a chapter presents a different impossible situation related to the chapter's topic, followed by the experts' suggested solutions (presented in the alphabetical order of the experts' last names). The Data Warehouse Glossary at the back of the book clarifies some terms and helps keep you from going down the wrong path. Misunderstanding the terminology