Home > Articles > Programming

Introduction to Data Model Patterns: Conventions of Thought

David Hay introduces his book, Data Model Patterns, which takes the position that the underlying structures of many businesses and government agencies are very similar, and that it should therefore be possible to model these similar structures in similar ways. Using common shapes for common situations makes the models easier to read, and it guides the modeler closer to identifying truly fundamental things.
This chapter is from the book

A data model is a representation of the things of significance to an enterprise and the relationships among those things. It portrays the underlying structure of the enterprise’s data, so this can then be reflected in the structure of databases built to support it.

This book takes the position that the underlying structures of many businesses and government agencies are very similar, and that it should therefore be possible to model these similar structures in similar ways. Using common shapes for common situations makes the models easier to read, and it guides the modeler closer to identifying truly fundamental things.

Data Modeling’s Promise—and Failure

Data modeling* serves two purposes in the systems analysis process: First, as a graphic technique, it aids in communication between analysts and the ultimate users of the systems they will specify, and between analysts and those who will design and build systems for those users. Second, as a rigorous technique, it imposes discipline on the specification of problems, ensuring due consideration of logical implications.

Creation of a data model is supposed to focus the user’s, the analyst’s, and the designer’s attention on things that are most fundamental to the nature of the business. The technique promises to lead to the development of stable, robust, and reliable information systems, so that normal changes in the business will not affect them. Moreover, data models promise to be useful as the basis for discussions among all three sets of players (users, analysts, and designers) about the future of information systems development in the organization. A data model can show, for example, the effect that a change to the organization will have on its information systems.

Alas, data modeling has not always kept these promises. If it is not used effectively, the technique neither improves communication nor imposes discipline.

Data modeling as currently practiced suffers from two problems:

  • Diagrams are often difficult to read.
  • Diagrams do not represent the fundamental nature of the organizations they are supposed to describe.

Herein lies the purpose of this book. It describes an approach to data modeling that can restore those promises by producing models that are both clearer than those produced without using this approach, and more likely to address fundamental issues.


As typically produced, data model diagrams can be less than inviting. While the use of graphics is supposed to make the ideas presented more accessible, the use of graphics without regard to aesthetic principles has the opposite effect. A mass of boxes and lines with no identifiable shape or organization aids in neither the understanding of an organization nor the planning of its future systems development efforts. A common reaction to the typical data model is: There are so many symbols! Where do I start? What is really going on here? How can I use this?

Defining a set of symbols to represent data structures is not enough. It is necessary to add a method for organizing those symbols, so that the reader of the model can deal with the drawing as a whole. It is also necessary to apply some aesthetic standards, in order to ensure that meaning encoded in the symbols can be accessible to the viewer.

Fundamentals of the Business

If you choose to build a new system, you want it to reflect the true requirements of your business—not simply to reproduce the techniques and technology now in use. The reason for making the investment in the first place is that you want to change the way things are done, without necessarily changing the nature of your enterprise.

A data model can help change the way things are done without affecting the nature of your business if it presents what is unchanging in an organization. It is intended to portray the things of significance, about which the company wishes to hold information. If the model succeeds, the things represented are unlikely to change significantly, either with the application of new technology (computer or other) or with the making of routine changes to the business of the organization. Technology whose architecture is based on what is fundamental will improve the operational aspects of an organization while remaining robust, stable, and flexible.

Unfortunately, what most people see in the course of their work (and consequently tell systems analysts about) is not this unchanging nature at all, but merely examples of it. They see only today’s problems, and the particular technology they must use to do their jobs—to the point that the technology becomes their job. Since the information an analyst gathers, therefore, is usually expressed in terms of current practices, distinguishing between what is essential to a business and what is merely an accident of current technology is not always easy. The essential facts are the things that “go without saying”—so they don’t get said. These facts don’t get described or explained—or reflected in new systems. Instead, new systems are often built on superficial views of today’s problems.

A plant that makes carbon black for printing ink and tires spent many weeks discussing the best ways to determine production rates and yields. The discussions concerned the best ways of predicting yield from the grade of natural gas that was used, but clearly something was not getting across. Finally, the manager let slip the fact that yield is also a function of the production unit used. The yield varies from unit to unit. This was obvious to him, so he didn’t mention it. Because it was not so obvious to the analyst, the original database design had not taken this into account and had to be substantially redone.

The elements of a business that are typically portrayed in data models reflect this difficulty. Instead of these essential facts about a business, model diagrams are often dominated by references to the objects that represent the particular way things are done now. A careless analyst may interpret transient things to be things of importance. The resulting model will reflect only those things that are important to current business practices.

A purchasing agent, for example, might describe the company’s purchasing system, giving special emphasis to its shortcomings (such as the fact that there may not be enough room on a purchase order for notes), while neglecting to describe the essential facts about a purchase order (such as the fact that “terms of sale” must appear). To build a new system based solely on the structure (and failings) of an existing system is to fail to take advantage of technological opportunities. Suppose, for example, purchasing were to do away with paper forms altogether and dial directly into vendors’ computers. What would remain essential to the transaction?

How Standards Can Help

Both communications and discipline can be improved. Moreover, we can make better use of each other’s work. What is needed is standardization of our approach to the modeling process. This does not mean simply using a common system of notation, although that would certainly help. What it means, rather, is using a common approach to the way we think about business situations, and to the way we organize our presentations of them. This book is about these “conventions of thought.” It identifies common situations that are present in a variety of businesses and government agencies, and which can be modeled in a standardized way. This standardization can make models both easier to read and more descriptive of what is fundamental to an enterprise.

The modeling conventions presented here are an attempt to establish that common approach to modeling. They do not represent the final models of any real company or agency. Rather, they are starting points, showing ways of looking at a business situation that should allow an analyst quickly to come to terms with the most important aspects of it. Having done so, the analyst is expected to apply creativity and imagination to adapt technology to those aspects.

Each chapter of the book presents concepts fundamental to a topic. It describes a typical business situation, provides basic models for portraying the situation, and enumerates variations that can be expected across different organizations.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020