View source for Unified Modeling Language

{{Short description|Software system design modeling tool}}
{{Redirect|UML}}
{{Use American English|date=March 2020}}
{{Use dmy dates|date=September 2020}}
{{Infobox programming language
| name = UML
| logo = UML logo.svg
| family = [[Modeling language]]
| website = {{URL|https://www.uml.org/}}
}}
The '''Unified Modeling Language''' ('''UML''') is a general-purpose visual [[modeling language]] that is intended to provide a standard way to visualize the design of a system.<ref name="OMG">{{cite book
|title=Unified Modeling Language 2.5.1
|series=[[Object Management Group|OMG]] Document Number formal/2017-12-05
|date=December 2017
|publisher=[[Object Management Group]] Standards Development Organization (OMG SDO)
|url=https://www.omg.org/spec/UML/2.5.1/PDF
}}</ref>

UML provides a standard notation for many types of diagrams which can be roughly divided into three main groups: behavior diagrams, interaction diagrams, and structure diagrams.

The creation of UML was originally motivated by the desire to standardize the disparate notational systems and approaches to software design. It was developed at [[Rational Software]] in 1994–1995, with further development led by them through 1996.<ref name=":1" />

In 1997, UML was adopted as a standard by the [[Object Management Group]] (OMG) and has been managed by this organization ever since. In 2005, UML was also published by the [[International Organization for Standardization]] (ISO) and the [[International Electrotechnical Commission]] (IEC) as the '''ISO/IEC 19501''' standard.<ref>{{cite web|url=http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=32620 |title=ISO/IEC 19501:2005 - Information technology - Open Distributed Processing - Unified Modeling Language (UML) Version 1.4.3 |publisher=Iso.org |date=2005-04-01 |access-date=2015-05-07}}</ref> Since then the standard has been periodically revised to cover the latest revision of UML.<ref>{{cite web|url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=32624 |title=ISO/IEC 19505-1:2012 - Information technology - Object Management Group Unified Modeling Language (OMG UML) - Part 1: Infrastructure |publisher=Iso.org |date=2012-04-20 |access-date=2014-04-10}}</ref>

In software engineering, most practitioners do not use UML, but instead produce informal hand drawn diagrams; these diagrams, however, often include elements from UML.<ref>{{cite book
|author1=Sebastian Baltes
|author2=Stephan Diehl
|title=Proceedings of the 22nd [[ACM SIGSOFT]] International Symposium on Foundations of Software Engineering
|chapter=Sketches and diagrams in practice
|date=2014-11-11
|chapter-url=https://doi.org/10.1145/2635868.2635891
|series=FSE 2014
|publisher=[[Association for Computing Machinery]]
|pages=530–541
|doi=10.1145/2635868.2635891
|isbn=978-1-4503-3056-5
|arxiv=1706.09172
|s2cid=2436333}}</ref>{{Rp|536}}

== History ==
[[File:OO Modeling languages history.jpg|thumb|320px|History of object-oriented methods and notation]]

=== Before UML 1.0 ===
UML has evolved since the second half of the 1990s and has its roots in the [[object-oriented programming]] methods developed in the late 1980s and early 1990s. The timeline (see image) shows the highlights of the history of object-oriented modeling methods and notation.

It is originally based on the notations of the [[Booch method]], the [[object-modeling technique]] (OMT), and [[object-oriented software engineering]] (OOSE), which it has integrated into a single language.<ref name=":0" />

[[Rational Software Corporation]] hired [[James Rumbaugh]] from [[General Electric]] in 1994 and after that, the company became the source for two of the most popular object-oriented modeling approaches of the day:<ref>Andreas Zendler (1997) ''Advanced Concepts, Life Cycle Models and Tools for Objeckt-Oriented Software Development''. p.&nbsp;122</ref> Rumbaugh's [[object-modeling technique]] (OMT) and [[Grady Booch]]'s method. They were soon assisted in their efforts by [[Ivar Jacobson]], the creator of the [[object-oriented software engineering]] (OOSE) method, who joined them at Rational in 1995.<ref name=":1">{{cite book
| title = Unified Modeling Language User Guide, The
| publisher = Addison-Wesley
| edition = 2
| year = 2005
| page = 496
| url = http://www.informit.com/store/unified-modeling-language-user-guide-9780321267979
| isbn = 0321267974
}}
See the sample content: look for history</ref>

=== UML 1.x ===
Under the technical leadership of those three (Rumbaugh, Jacobson, and Booch), a consortium called the [[UML Partners]] was organized in 1996 to complete the ''Unified Modeling Language (UML)'' specification and propose it to the Object Management Group (OMG) for standardization. The partnership also contained additional interested parties (for example [[Hewlett-Packard|HP]], [[Digital Equipment Corporation|DEC]], [[IBM]], and [[Microsoft]]). The UML Partners' UML 1.0 draft was proposed to the OMG in January 1997 by the consortium. During the same month, the UML Partners formed a group, designed to define the exact meaning of language constructs, chaired by [[Cris Kobryn]] and administered by Ed Eykholt, to finalize the specification and integrate it with other standardization efforts. The result of this work, UML 1.1, was submitted to the OMG in August 1997 and adopted by the OMG in November 1997.<ref name=":1" /><ref>{{cite web|url=http://www.omg.org/cgi-bin/doc?ad/97-08-11 |title=UML Specification version 1.1 (OMG document ad/97-08-11) |publisher=Omg.org |access-date=2011-09-22}}</ref>

After the first release, a task force was formed<ref name=":1" /> to improve the language, which released several minor revisions, 1.3, 1.4, and 1.5.<ref>{{cite web|url=http://www.omg.org/spec/UML/ |title=UML |publisher=Omg.org |access-date=2014-04-10}}</ref>

The standards it produced (as well as the original standard) have been noted as being ambiguous and inconsistent.<ref>Génova et alia 2004 "Open Issues in Industrial Use Case Modeling"</ref>

==== Cardinality notation ====
As with database Chen, Bachman, and ISO [[ER diagram]]s, class models are specified to use "look-across" [[Cardinality (data modeling)|cardinalities]], even though several authors ([[Merise]],<ref>Hubert Tardieu, Arnold Rochfeld and René Colletti La methode MERISE: Principes et outils (Paperback - 1983)</ref>
Elmasri & Navathe,<ref>Elmasri, Ramez, B. Shamkant, Navathe, Fundamentals of Database Systems, third ed., Addison-Wesley, Menlo Park, CA, USA, 2000.</ref>
amongst others<ref>{{cite book
|title=Conceptual Modeling – ER 2004: 23rd International Conference on Conceptual Modeling, Shanghai, China, November 8–12, 2004
|publisher=[[Springer Publishing|Springer]]
|date=October 27, 2004
|series=[[Lecture Notes in Computer Science]] 3288
|edition=2004
|isbn=3540237232
|editor1=Paolo Atzeni
|editor2=Wesley Chu
|editor3=Hongjun Lu
|editor4=Shuigeng Zhou
|editor5=Tok Wang Ling
}}</ref>)
prefer same-side or "look-here" for roles and both minimum and maximum cardinalities. Recent researchers (Feinerer<ref>{{cite thesis
|author=Ingo Feinerer
|title=A Formal Treatment of UML Class Diagrams as an Efficient Method for Configuration Management
|url=https://publik.tuwien.ac.at/files/pub-inf_4582.pdf
|date=March 2007
|location=Vienna
|degree=Doctor of Technical Sciences
|publisher=Technical University of Vienna}}</ref>
and Dullea et al.<ref>{{cite journal
|journal=Data & Knowledge Engineering
|volume=47
|issue=2
|title=An analysis of structural validity in entity-relationship modeling
|author1=James Dullea
|author2=Il-Yeol Song
|author3=Ioanna Lamprou
|date=November 1, 2003
|pages=167–205
|doi=10.1016/S0169-023X(03)00049-1}}</ref>)
have shown that the "look-across" technique used by UML and ER diagrams is less effective and less coherent when applied to ''n''-ary relationships of order strictly greater than 2.

Feinerer says: "Problems arise if we operate under the look-across semantics as used for UML associations. Hartmann<ref>{{cite conference
|conference=ADC '03: Proceedings of the 14th Australasian database conference
|author=Sven Hartmann
|publisher=[[Australian Computer Society]]
|url=https://dl.acm.org/doi/abs/10.5555/820085.820110
|title=Reasoning about participation constraints and Chen's constraints
|date=January 17, 2003
|pages=105–113}} {{open access}}</ref>
investigates this situation and shows how and why different transformations fail.", and: "As we will see on the next few pages, the look-across interpretation introduces several difficulties which prevent the extension of simple mechanisms from binary to ''n''-ary associations."

=== UML 2 ===
UML 2.0 major revision replaced version 1.5 in 2005, which was developed with an enlarged consortium to improve the language further to reflect new experiences on the usage of its features.<ref>{{cite web|url=http://www.omg.org/spec/UML/2.0/ |title=UML 2.0 |publisher=Omg.org |access-date=2011-09-22}}</ref>

Although UML 2.1 was never released as a formal specification, versions 2.1.1 and 2.1.2 appeared in 2007, followed by UML 2.2 in February 2009. UML 2.3 was formally released in May 2010.<ref name="spec">{{cite web|url=http://www.omg.org/spec/UML/ |title=UML |publisher=Omg.org |access-date=2011-09-22}}</ref> UML 2.4.1 was formally released in August 2011.<ref name="spec" /> UML 2.5 was released in October 2012 as an "In progress" version and was officially released in June 2015.<ref name="spec" />
The formal version 2.5.1 was adopted in December 2017.<ref name="OMG" />

There are four parts to the UML 2.x specification:

* The Superstructure that defines the notation and semantics for diagrams and their model elements
* The Infrastructure that defines the core metamodel on which the Superstructure is based
* The [[Object Constraint Language]] (OCL) for defining rules for model elements
* The UML Diagram Interchange that defines how UML 2 diagram layouts are exchanged

Until UML 2.4.1, the latest versions of these standards were:<ref name="Versions2.4.1">{{cite web|author=OMG|title=OMG Formal Specifications (Modeling and Metadata paragraph)|url=http://www.omg.org/spec/#M&M|access-date = 2016-02-12}}</ref>
* UML Superstructure version 2.4.1
* UML Infrastructure version 2.4.1
* OCL version 2.3.1
* UML Diagram Interchange version 1.0.
Since version 2.5, the UML Specification has been simplified (without Superstructure and Infrastructure), and the latest versions of these standards are now:<ref name="LatestVersions">{{cite web|author=OMG|title=about the unified modeling language specification|url=https://www.omg.org/spec/UML/About-UML/|access-date = 2020-02-22}}</ref>

* UML Specification 2.5.1
* OCL version 2.4

It continues to be updated and improved by the revision task force, who resolve any issues with the language.<ref>{{cite web |title=Issues for UML 2.6 Revision task Force mailing list |url=https://issues.omg.org/issues/lists/uml2-rtf |access-date=2014-04-10 |publisher=Omg.org}}</ref>

== Design ==
[[File:Component-based-Software-Engineering-example2.png|class=skin-invert-image|thumb|500px|An example of components in a travel reservation system]]

UML offers a way to visualize a system's architectural blueprints in a diagram, including elements such as:<ref name=":0">{{cite web|url=http://www.omg.org/spec/UML/2.4.1/Superstructure/PDF |title=OMG Unified Modeling Language (OMG UML), Superstructure. Version 2.4.1 |publisher=Object Management Group |access-date=9 April 2014}}</ref>

* any [[Activity (UML)|activities]] (jobs);
* individual [[Component (UML)|components]] of the system;
** and how they can interact with other [[software component]]s;
* how the system will run;
* how entities interact with others (components and interfaces);
* external [[user interface]].

Although originally intended for object-oriented design documentation, UML has been extended to a larger set of design documentation (as listed above),<ref>Satish Mishra (1997). [http://www2.informatik.hu-berlin.de/~hs/Lehre/2004-WS_SWQS/20050107_Ex_UML.ppt "Visual Modeling & Unified Modeling Language (UML): Introduction to UML"] {{Webarchive|url=https://web.archive.org/web/20110720091651/http://www2.informatik.hu-berlin.de/~hs/Lehre/2004-WS_SWQS/20050107_Ex_UML.ppt |date=20 July 2011 }}. Rational Software Corporation. Accessed 9 November 2008.</ref> and has been found useful in many contexts.<ref name="UML, Success Stories">{{cite web|url=http://www.uml.org/uml_success_stories/index.htm|title=UML, Success Stories|access-date=9 April 2014}}</ref>

=== Software development methods ===
UML is not a development method by itself;<ref>John Hunt (2000). ''The Unified Process for Practitioners: Object-oriented Design, UML and Java''. Springer, 2000. {{ISBN|1-85233-275-1}}. p.&nbsp;5.door</ref> however, it was designed to be compatible with the leading object-oriented software development methods of its time, for example, [[Object-modeling technique|OMT]], [[Booch method]], [[Objectory]], and especially [[Rational Unified Process|RUP]] it was originally intended to be used with when work began at Rational Software.

=== Modeling ===
It is important to distinguish between the UML model and the set of diagrams of a system. A diagram is a partial graphic representation of a system's model. The set of diagrams need not completely cover the model and deleting a diagram does not change the model. The model may also contain documentation that drives the model elements and diagrams (such as written use cases).

UML diagrams represent two different views of a system model:<ref>Jon Holt Institution of Electrical Engineers (2004). ''UML for Systems Engineering: Watching the Wheels'' IET, 2004, {{ISBN|0-86341-354-4}}. p.&nbsp;58</ref>

* Static (or ''structural'') view: emphasizes the static structure of the system using objects, attributes, operations and relationships. It includes [[class diagram]]s and [[composite structure diagram]]s.
* Dynamic (or ''behavioral'') view: emphasizes the dynamic behavior of the system by showing collaborations among objects and changes to the internal states of objects. This view includes [[sequence diagram]]s, [[activity diagram]]s and [[UML state machine|state machine diagrams]].

UML models can be exchanged among [[UML tool]]s by using the [[XML Metadata Interchange]] (XMI) format.

In UML, one of the key tools for behavior modeling is the use-case model, caused by [[OOSE]]. Use cases are a way of specifying required usages of a system. Typically, they are used to capture the requirements of a system, that is, what a system is supposed to do.<ref>Manuel Almendros-Jiménez, Jesús & Iribarne, Luis. (2007). Describing Use-Case Relationships with Sequence Diagrams. Comput. J.. 50. 116-128. 10.1093/comjnl/bxl053.</ref>

== Diagrams ==
{{UML diagram types}}

UML 2 has many types of diagrams, which are divided into two categories.<ref name=":0" /> Some types represent ''structural'' information, and the rest represent general types of ''behavior'', including a few that represent different aspects of ''interactions''. These diagrams can be categorized hierarchically as shown in the following class diagram:<ref name=":0" />

[[File:UML diagrams overview.svg|class=skin-invert-image|center|600px|Hierarchy of UML 2.2 Diagrams, shown as a [[class diagram]]]]

These diagrams may all contain comments or notes explaining usage, constraint, or intent.

=== Structure diagrams ===
Structure diagrams represent the static aspects of the system. It emphasizes the things that must be present in the system being modeled. Since structure diagrams represent the structure, they are used extensively in documenting the [[software architecture]] of software systems. For example, the [[component diagram]] describes how a software system is split up into components and shows the dependencies among these components.

<gallery class="center skin-invert-image" style="width: initial">
Policy Admin Component Diagram.PNG|[[Component diagram]]
BankAccount1.svg|[[Class diagram]]
</gallery>

=== Behavior diagrams ===
Behavior diagrams represent the dynamic aspect of the system. It emphasizes what must happen in the system being modeled. Since behavior diagrams illustrate the behavior of a system, they are used extensively to describe the functionality of software systems. As an example, the [[activity diagram]] describes the business and operational step-by-step activities of the components in a system.

<gallery class="center skin-invert-image" style="width: initial">
Activity conducting.svg|[[Activity diagram]]
UML Use Case diagram.svg|[[Use case diagram]]
</gallery>

Visual Representation: Staff User → Complaints System: Submit Complaint Complaints System → HR System: Forward Complaint HR System → Department: Assign Complaint Department → Complaints System: Update Resolution Complaints System → Feedback System: Request Feedback Feedback System → Staff User: Provide Feedback Staff User → Feedback System: Submit Feedback. This description can be used to draw a sequence diagram using tools like Lucidchart, Draw.io, or any UML diagram software. The diagram would have actors on the left side, with arrows indicating the sequence of actions and interactions between systems and actors as described. Sequence diagrams should be drawn for each use case to show how different objects interact with each other to achieve the functionality of the use case.

== Artifacts ==
[[File:UML Artifact.PNG|thumb|320px|Artifact manifesting components]]

In UML, an '''artifact'''<ref name="OMG_Artifacts">{{cite book
|chapter=Artifacts
|title=Unified Modeling Language 2.5.1
|series=[[Object Management Group|OMG]] Document Number formal/2017-12-05
|date=December 2017
|publisher=[[Object Management Group]] Standards Development Organization (OMG SDO)
|page=656
|url=https://www.omg.org/spec/UML/2.5.1/PDF
}}</ref>
is the "specification of a physical piece of information that is used or produced by a [[software development process]], or by deployment and operation of a system."<ref name="OMG_Artifacts" />

"Examples of artifacts include model files, [[source code|source]] files, scripts, and [[binary executable]] files, a [[Table (database)|table]] in a [[database system]], a development deliverable, a [[word-processing]] [[document]], or a [[mail]] message."<ref name="OMG_Artifacts" />

Artifacts are the physical entities that are deployed on
[[Node (UML)|Nodes]]<ref name="OMG_Artifacts" />
(i.e. Devices and Execution Environments).
Other UML elements such as classes and components are first manifested into artifacts and instances of these artifacts are then deployed. Artifacts can also be composed of other artifacts.

== Metamodeling ==
{{Main|Meta-Object Facility}}

[[File:M0-m3.png|thumb|320px|Illustration of the Meta-Object Facility]]

The [[Object Management Group]] (OMG) has developed a [[metamodeling]] architecture to define the UML, called the [[Meta-Object Facility]].<ref>Iman Poernomo (2006) "[http://calcium.dcs.kcl.ac.uk/1259/1/acm-paper.pdf The Meta-Object Facility Typed] {{Webarchive|url=https://web.archive.org/web/20160630002118/http://calcium.dcs.kcl.ac.uk/1259/1/acm-paper.pdf |date=30 June 2016 }}" in: ''Proceeding SAC '06 Proceedings of the 2006 ACM symposium on Applied computing''. pp. 1845–1849</ref> MOF is designed as a four-layered architecture, as shown in the image at right. It provides a meta-meta model at the top, called the M3 layer. This M3-model is the language used by Meta-Object Facility to build metamodels, called M2-models.

The most prominent example of a Layer 2 Meta-Object Facility model is the UML metamodel, which describes the UML itself. These M2-models describe elements of the M1-layer, and thus M1-models. These would be, for example, models written in UML. The last layer is the M0-layer or data layer. It is used to describe runtime instances of the system.<ref>{{cite web|url=http://www.omg.org/spec/UML/2.4.1/Infrastructure/PDF/ |title=UML 2.4.1 Infrastructure |publisher=Omg.org |date=2011-08-05 |access-date=2014-04-10}}</ref>

The meta-model can be extended using a mechanism called [[stereotype (UML)|stereotyping]]. This has been criticized as being insufficient/untenable by [[Brian Henderson-Sellers]] and Cesar Gonzalez-Perez in "Uses and Abuses of the Stereotype Mechanism in UML 1.x and 2.0".<ref name="UsesAbusesStereotype">{{cite journal
|author1=[[Brian Henderson-Sellers]]
|author2=Cesar Gonzalez-Perez
|title=Uses and abuses of the stereotype mechanism in UML 1.x and 2.0
|date=October 1, 2006
|journal=MoDELS '06: Proceedings of the 9th International Conference on Model Driven Engineering Languages and Systems
|pages=16–26
|doi=10.1007/11880240_2
|publisher=[[Springer-Verlag]]
|series=[[Lecture Notes in Computer Science]] 4199
|volume=4199
|location=[[Berlin]], Germany|isbn=978-3-540-45772-5
}}</ref>

== Adoption ==
In 2013, UML had been marketed by OMG for many contexts, but aimed primarily at software development with limited success.<ref name="UML, Success Stories" /><ref>{{Cite web|url = http://www.drdobbs.com/architecture-and-design/uml-25-do-you-even-care/240163702?queryText=uml|title = UML 2.5: Do you even care?| work=Dr. Dobb's }} "UML truly is ubiquitous"</ref>

It has been treated, at times, as a design [[no silver bullet|silver bullet]], which leads to problems. UML misuse includes overuse (designing every part of the system with it, which is unnecessary) and assuming that novices can design with it.<ref>{{Cite web|url = http://queue.acm.org/detail.cfm?id=984495|title = Death by UML Fever}}</ref>

It is considered a large language, with many [[Syntax (programming languages)|constructs]]. Some people (including [[Ivar Jacobson|Jacobson]]) feel that UML's size hinders learning and therefore uptake.<ref>{{Cite web|url = http://www.infoq.com/interviews/Ivar_Jacobson|title = Ivar Jacobson on UML, MDA, and the future of methodologies}}</ref>

MS Visual Studio dropped support for UML in 2016 due to lack of usage.<ref>{{Cite web |last=Krill |first=Paul |date=2016-10-18 |title=UML to be ejected from Microsoft Visual Studio |url=https://www.infoworld.com/article/3131600/uml-to-be-ejected-from-microsoft-visual-studio.html |access-date=2023-07-23 |website=InfoWorld |language=en}}</ref>

According to [[Google Trends]], UML has been on a steady decline since 2004.<ref>{{Cite web |title=Google Trends |url=https://trends.google.com/trends/explore?date=all&geo=US&q=UML&hl=en |access-date=2023-07-23 |website=Google Trends |language=en-US |archive-date=23 July 2023 |archive-url=https://web.archive.org/web/20230723193301/https://trends.google.com/trends/explore?date=all&geo=US&q=UML&hl=en |url-status=dead }}</ref>

== See also ==
* [[Applications of UML]]
* [[Business Process Model and Notation|BPMN (Business Process Model and Notation)]]
* [[C4 model]]
* [[Department of Defense Architecture Framework]]
* [[DOT (graph description language)]]
* [[List of Unified Modeling Language tools]]
* [[MODAF]]
* [[Model-based testing]]
* [[Model-driven engineering]]
* [[Object-oriented role analysis and modeling]]
* [[Process Specification Language]]
* [[Systems Modeling Language]] (SysML)

== References ==
{{Reflist}}

== Further reading ==
* {{cite book
| first = Scott William
| last = Ambler
| year = 2004
| url = http://www.ambysoft.com/books/theObjectPrimer.html
| title = The Object Primer: Agile Model Driven Development with UML 2
| publisher = Cambridge University Press
| isbn = 0-521-54018-6
| access-date = 29 April 2006
| archive-date = 31 January 2010
| archive-url = https://web.archive.org/web/20100131215505/http://www.ambysoft.com/books/theObjectPrimer.html
| url-status = dead
}}
* {{cite book
| first = Michael Jesse
| last = Chonoles
| author2 = James A. Schardt
| year = 2003
| title = UML 2 for Dummies
| publisher = Wiley Publishing
| isbn = 0-7645-2614-6
| url = https://archive.org/details/uml2fordummies00chon
}}
* {{cite book
| first = Martin
| last = Fowler
| author-link = Martin Fowler (software engineer)
| title = UML Distilled: A Brief Guide to the Standard Object Modeling Language
| year = 2004
| edition = 3rd
| publisher = Addison-Wesley
| isbn = 0-321-19368-7
}}
* {{cite book
| first= Ivar
| last = Jacobson |author2=Grady Booch |author3=James Rumbaugh
| author-link = Ivar Jacobson
| year = 1998
| title = The Unified Software Development Process
| publisher = Addison Wesley Longman
| isbn=0-201-57169-2
}}
* {{cite book
| first = Robert Cecil
| last = Martin
| author-link = Robert Cecil Martin
| year = 2003
| title = UML for Java Programmers
| publisher = Prentice Hall
| isbn = 0-13-142848-9
| url = https://archive.org/details/umlforjavaprogra00mart
}}
* {{cite web
| author = Noran, Ovidiu S.
| url = https://www.area-c54.it/public/business%20modelling%20-%20uml%20vs%20idef.pdf
| title = Business Modelling: UML vs. IDEF
| access-date = 2022-11-14
}}
* {{cite web
| author = Horst Kargl
| url = http://umlnotation.sparxsystems.eu/
| title = Interactive UML Metamodel with additional Examples
}}
* {{cite book
| first = Magnus
| last = Penker
| author2 = Hans-Erik Eriksson
| author-link2 = Hans-Erik Eriksson
| year = 2000
| title = Business Modeling with UML
| publisher = John Wiley & Sons
| isbn = 0-471-29551-5
| url = https://archive.org/details/businessmodeling00erik
}}
* {{cite web
| author = Douglass, Bruce Powel
| url = https://www.bruce-douglass.com/
| title = Bruce Douglass: Real-Time Agile Systems and Software Development
| format = web
| access-date = 2019-01-01
}}
* {{cite book
| first = Bruce
| last = Douglass
| year = 2014
| title = Real-Time UML Workshop 2nd Edition
| publisher = Newnes
| isbn = 978-0-471-29551-8
| url = https://archive.org/details/businessmodeling00erik
| url-access = registration
}}
* {{cite book
| first = Bruce
| last = Douglass
| year = 2004
| title = Real-Time UML 3rd Edition
| publisher = Newnes
| isbn =  978-0321160768
}}
* {{cite book
| first = Bruce
| last = Douglass
| year = 2002
| title = Real-Time Design Patterns
| publisher = Addison-Wesley Professional
| isbn = 978-0201699562
}}
* {{cite book
| first = Bruce
| last = Douglass
| year = 2009
| title = Real-Time Agility
| publisher = Addison-Wesley Professional
| isbn =  978-0321545497
}}
* {{cite book
| first = Bruce
| last = Douglass
| year = 2010
| title = Design Patterns for Embedded Systems in C
| publisher = Newnes
| isbn =  978-1856177078
}}

== External links ==
{{Commons}}
{{Wikiversity|UML}}
* {{Official website}}
* Current UML specification: {{cite book
|title=Unified Modeling Language 2.5.1
|series=[[Object Management Group|OMG]] Document Number formal/2017-12-05
|date=December 2017
|publisher=[[Object Management Group]] Standards Development Organization (OMG SDO)
|url=https://www.omg.org/spec/UML/2.5.1/PDF
}}

{{UML}}
{{Software engineering}}
{{ISO standards}}
{{Authority control}}

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