Home > Articles > Software Development & Management > UML

Introduction to the UML

📄 Contents

  1. What Is the Unified Modeling Language (UML)?
  2. What Is a Model?
  3. What Is a Diagram?
  4. Terms
  5. Summary
  6. Review Questions
This chapter provides an overview of Unified Modeling Language (UML), a graphical language for modeling businesses, software applications, and system architectures.
This chapter is from the book

This chapter is from the book

Topics Covered in This Chapter

  • What Is the Unified Modeling Language (UML)?
    • Where Did the UML Come From?
    • Is the UML Proprietary?
    • Is the UML Only for Object-Oriented Development?
    • Is the UML a Methodology?
    • What Is Happening Now with the UML?
  • What Is a Model?
    • Why Should I Build Models?
    • Why Should I Model with the UML?
    • What Can I Model with the UML?
    • Who Should Build Models?
  • What Is a Diagram?
    • What Diagrams Are in the UML?
    • What Is the Difference Between Diagrams and Models?
  • Terms
  • Summary
  • Review Questions

What Is the Unified Modeling Language (UML)?

The Unified Modeling Language (UML) is the standard visual modeling language used for modeling businesses, software applications, and system architectures. Although the UML is a standard of the Object Management Group (OMG—http://www.omg.org/), the UML is not just for modeling object-oriented (OO) software applications. The UML is a graphical language that was designed to be very flexible and customizable. This enables you to create many different types of models, including models for understanding business processes, workflow, sequences of queries, applications, databases, architectures, and more.

Where Did the UML Come From?

To understand the UML, it helps to know its origins. During the late 1980s and into the 1990s, many object-oriented modeling techniques were being developed to model software. Because different people developed these approaches using different visual modeling techniques and notations, the world of application modeling was becoming divided. To further complicate matters, some techniques were designed just for application modeling, and others were targeted at specific areas such as database design. Some leveraged the strengths of the others, but some remained distinct.

Three of these methodologies began to lead the pack in the marketplace. While working for General Electric, Jim Rumbaugh created the Object Modeling Technique (OMT). Ivar Jacobson developed his Object-Oriented Software Engineering method (a.k.a. the Objectory Method), primarily supporting the telecommunicationsindustry in Sweden. Grady Booch developed the self-named Booch Method. Each had their strengths and weaknesses, and each had somewhat different followings.

In the mid 1990s, Rational Software hired Jim Rumbaugh to join Grady Booch and combine their modeling methods into what became version 0.8, the first public draft of what was then called the Unified Method. In 1995, Jacobson joined Rumbaugh and Booch at Rational. Together, they developed version 0.9 of the Unified Method in 1996. Other companies joined Booch, Rumbaugh, and Jacobson as part of the UML Consortium. In 1997, they submitted version 1.0 of the Unified Method—renamed as the Unified Modeling Language, or UML—to the OMG. As an independent standards body, the OMG took over the UML development and released subsequent versions of the UML (see Figure 1-1). This year (2004), the final approval of the latest version, UML 2.0, is expected.

What makes the UML different from the independent notations we mentioned earlier is that the UML is the creation not of just Booch, Rumbaugh, and Jacobson, but also of many industry experts, software development tool companies, corporate software development organizations, and others. So began the worldwide standard modeling language of software development.

Figure 1.1Figure 1-1 History of the UML.

Is the UML Proprietary?

As you decide whether to use the UML to model, one of the main things you need to consider is whether other people who join your organization will be able to understand what you have done and whether it will be communicated unambiguously. Both are good reasons for wanting to select a modeling language that is in the public domain and that is understood around the world.

As we discussed earlier in this chapter, the UML was designed because the different modeling languages that were available at the time were leading to a divergence in the ways to model. However, bringing the three major methods together wasn't quite enough. That is why Rational sought out the involvement of organizations such as IBM, Oracle, Platinum Technologies, and many others to be UML partners in the creation of the UML. They then handed development to the OMG to ensure that the UML would become a standard. As a result, the UML is not proprietary. It is an open modeling standard designed and supported by software companies, consultants, other corporations, and governments who need and rely on this standard.

Although a standard open language is critical to protect you from being locked in by the whims of a technology vendor, having a modeling language that is flexible also is key. As technologies and businesses change, so does the way you model. The UML has conventions built into it that enable you to customize it as needed. These customized versions are created using "stereotypes." You will learn more about them in Chapter 5, "Application Modeling."

Is the UML Only for Object-Oriented Development?

We travel the world talking about modeling and the UML. When we begin to discuss using the UML for business or data modeling (both of which we cover in later chapters), one of the first questions we hear is, "How would I use the UML for that? Isn't it only for object-oriented development?" This is one of the biggest myths we run across. The myth comes from the reality that the UML was devised to satisfy the need to model object-oriented systems and to enable Component-Based Development (CBD). In an OO system, generally several components are tied together using what are called "interfaces." To understand how those different components interact, it is quite useful to build a model.

Although the UML was originally built for this cause, it also was built with other needs in mind. Grady Booch once told us that when he and his colleagues were designing the UML, they based a lot of what they did on the different database modeling techniques already being used in the industry. Similarly, one of the strengths of Jacobson's Objectory Method was its business modeling capability. So when they added elements of Jacobson's Objectory Method to the UML mix, they added business modeling to UML.

Today, you can model almost anything you want to in the UML by using its built-in extension and customization capabilities. The UML features an underlying meta-model (see the "Deep Dive" sidebar on meta-models later in this chapter) that enables the UML to be flexible enough so that you can do what you need to do with it. We have seen the UML used for modeling businesses, data, organizations, theoretical political systems, legal contracts, biological systems, languages, hardware, non-object-oriented application modeling such as COBOL, and many other modeling tasks.

Is the UML a Methodology?


  • "Methodology n.

    • 1a. A body of practices, procedures, and rules used by those who work in a discipline or engage in an inquiry; a set of working methods: the methodology of genetic studies; a poll marred by faulty methodology.

    • b. The study or theoretical analysis of such working methods.

    • 2. The branch of logic that deals with the general principles of the formation of knowledge.

    • 3. Usage Problem...

    • Methodology can properly refer to the theoretical analysis of the methods appropriate to a field of study or to the body of methods and principles particular to a branch of knowledge. ... In recent years, however, methodology has been increasingly used as a pretentious substitute for method in scientific and technical contexts, as in The oil company has not yet decided on a methodology for restoring the beaches. ... But the misuse of methodology obscures an important conceptual distinction between the tools of scientific investigation (properly methods) and the principles that determine how such tools are deployed and interpreted." [AMER1]

This very typical definition of the term methodology explains that a methodology is much more than a language. You can see from the "usage problem" discussed in this definition how this can confuse some people who are new to the UML. The UML is a language. Object-oriented analysis and design (OOAD) is a process, governed by specific practices. Although languages, including the UML, have rules for syntax and usage, they do not have procedures (i.e., processes) or practices. A methodology must include these things as well. So, although a common language is needed in a specific discipline, language alone does not make a methodology. This is true for the UML as well. Thus, you can use the UML with various methodologies, but it is not a methodology itself.

What Is Happening Now with the UML?

As of this writing, the UML is in the final stages of approval for its latest revision, version 2.0. The OMG has been developing this version of the UML for many years. It combines the efforts of more than 100 organizations, bringing together the best practices they developed over the first few versions of the UML as well as needs they identified for the future.

Along with enhancing the UML infrastructure, adding new modeling capabilities, and enabling the easier exchange of models (i.e., between tools or systems), one of the OMG's main goals when developing UML 2.0 was to make it more extensible to accommodate present as well as future needs. For example, one long-standing need that is being addressed is the use of the UML to model embedded systems. (Unlike general-purpose systems such as desktop computers, embedded systems are special-purpose systems such as pacemakers, automotive braking systems, digital cameras, cruise missiles, mobile phones, and so forth that contain hardware and software designed to perform specific functions.) Typically, you would model embedded systems using different languages. But in the on-demand world of today, where you need to link your embedded systems with business systems in your organization, you need to understand how everything works together. This is greatly simplified if you model everything in the same language because it enables you to share information across different types of technologies and different modeling efforts. Prior to version 2.0, the UML provided some of this capability, but the additions the OMG made to the language in version 2.0 have greatly increased this capability.

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