![UML logo](https://upload.wikimedia.org/wikipedia/commons/d/d5/UML_logo.svg)
The Unified Modeling Language (UML) is a general-purpose, developmental
modeling language
A modeling language is any artificial language that can be used to express information or knowledge or systems in a structure that is defined by a consistent set of rules. The rules are used for interpretation of the meaning of components in the st ...
in the field of
software engineering
Software engineering is a systematic engineering approach to software development.
A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term '' ...
that is intended to provide a standard way to visualize the design of a system.
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
Rational Machines is an enterprise founded by Paul Levy and Mike Devlin in 1981 to provide tools to expand the use of modern software engineering practices, particularly explicit modular architecture and iterative development. It changed its ...
in 1994–1995, with further development led by them through 1996.
In 1997, UML was adopted as a standard by the
Object Management Group
The Object Management Group (OMG) is a computer industry standardization, standards consortium. OMG Task Forces develop enterprise integration standards for a range of technologies.
Business activities
The goal of the OMG was a common portabl ...
(OMG), and has been managed by this organization ever since. In 2005, UML was also published by the
International Organization for Standardization
The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Ar ...
(ISO) as an approved ISO standard. Since then the standard has been periodically revised to cover the latest revision of UML. In software engineering, most practitioners do not use UML, but instead produce informal hand drawn diagrams; these diagrams, however, often include elements from UML.
History
Before UML 1.0
UML has been evolving since the second half of the 1990s and has its roots in the
object-oriented programming
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pr ...
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 Booch method is a method for object-oriented software development. It is composed of an object modeling language, an iterative object-oriented development process, and a set of recommended practices.
The method was authored by Grady Booch wh ...
, the
object-modeling technique
The object-modeling technique (OMT) is an object modeling approach for software modeling and designing. It was developed around 1991 by Rumbaugh, Blaha, Premerlani, Eddy and Lorensen as a method to develop object-oriented systems and to support ...
(OMT) and
object-oriented software engineering
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pro ...
(OOSE), which it has integrated into a single language.
Rational Software Corporation
Rational Machines is an enterprise founded by Paul Levy and Mike Devlin in 1981 to provide tools to expand the use of modern software engineering practices, particularly explicit modular architecture and iterative development. It changed its ...
hired
James Rumbaugh
James E. Rumbaugh (born August 22, 1947) is an American computer scientist and object-oriented methodologist[General Electric
General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...](_blank)
in 1994 and after that the company became the source for two of the most popular object-oriented modeling approaches of the day: Rumbaugh's
object-modeling technique
The object-modeling technique (OMT) is an object modeling approach for software modeling and designing. It was developed around 1991 by Rumbaugh, Blaha, Premerlani, Eddy and Lorensen as a method to develop object-oriented systems and to support ...
(OMT) and
Grady Booch
Grady Booch (born February 27, 1955) is an American software engineer, best known for developing the Unified Modeling Language (UML) with Ivar Jacobson and James Rumbaugh. He is recognized internationally for his innovative work in software archit ...
's method. They were soon assisted in their efforts by
Ivar Jacobson
Ivar Hjalmar Jacobson (born 1939) is a Swedish computer scientist and software engineer, known as major contributor to UML, Objectory, Rational Unified Process (RUP), aspect-oriented software development and Essence.
Biography
Ivar Jacobson w ...
, the creator of the
object-oriented software engineering
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pro ...
(OOSE) method, who joined them at Rational in 1995.
[
, See the sample content, look for history]
UML 1.x
Under the technical leadership of those three (Rumbaugh, Jacobson and Booch), a consortium called the
UML Partners UML Partners was a consortium of system integrators and vendors convened in 1996 to specify the Unified Modeling Language (UML).
Initially the consortium was led by Grady Booch, Ivar Jacobson, and James Rumbaugh of Rational Software. The UML Partne ...
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
HP,
DEC,
IBM and
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
). 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
Cris Kobryn (1952) is an American technologist, system architect and entrepreneur who specializes in advanced software and systems development.
Biography
Kobryn began his software engineering career in the early 1980s specializing in AI program ...
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.
After the first release a task force was formed
to improve the language, which released several minor revisions, 1.3, 1.4, and 1.5.
The standards it produced (as well as the original standard) have been noted as being ambiguous and inconsistent.
Cardinality notation
As with database Chen, Bachman, and ISO
ER diagrams, class models are specified to use "look-across"
cardinalities
In mathematics, the cardinality of a set is a measure of the number of elements of the set. For example, the set A = \ contains 3 elements, and therefore A has a cardinality of 3. Beginning in the late 19th century, this concept was generalized ...
, even though several authors (
Merise
Merise () is a general-purpose modeling methodology in the field of information systems development, software engineering and project management. First introduced in the early 1980s, it was widely used in France, and was developed and refined to ...
, Elmasri & Navathe amongst others) prefer same-side or "look-here" for roles and both minimum and maximum cardinalities. Recent researchers (Feinerer, Dullea et al.) 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 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 experience on usage of its features.
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.
UML 2.4.1 was formally released in August 2011.
UML 2.5 was released in October 2012 as an "In progress" version and was officially released in June 2015.
Formal version 2.5.1 was adopted in December 2017.
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
The Object Constraint Language (OCL) is a declarative language describing rules applying to Unified Modeling Language (UML) models developed at IBM and is now part of the UML standard. Initially, OCL was merely a formal specification language ex ...
(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:
* 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:
* 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.
Design
UML offers a way to visualize a system's architectural blueprints in a diagram, including elements such as:
* any
activities (jobs);
* individual
components
Circuit Component may refer to:
•Are devices that perform functions when they are connected in a circuit.
In engineering, science, and technology Generic systems
* System components, an entity with discrete structure, such as an assem ...
of the system;
** and how they can interact with other
software components
Component-based software engineering (CBSE), also called component-based development (CBD), is a branch of software engineering that emphasizes the separation of concerns with respect to the wide-ranging functionality available throughout a give ...
;
* how the system will run;
* how entities interact with others (components and interfaces);
* external
user interface
In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine f ...
.
Although originally intended for object-oriented design documentation, UML has been extended to a larger set of design documentation (as listed above), and been found useful in many contexts.
Software development methods
UML is not a development method by itself; however, it was designed to be compatible with the leading object-oriented software development methods of its time, for example
OMT,
Booch method
The Booch method is a method for object-oriented software development. It is composed of an object modeling language, an iterative object-oriented development process, and a set of recommended practices.
The method was authored by Grady Booch wh ...
,
Objectory
Objectory is an object-oriented methodology mostly created by Ivar Jacobson, who has greatly contributed to object-oriented software engineering
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", wh ...
and especially
RUP that 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:
* Static (or ''structural'') view: emphasizes the static structure of the system using objects, attributes, operations and relationships. It includes
class diagram
In software engineering, a class diagram in the Unified Modeling Language (UML) is a type of static structure diagram that describes the structure of a system by showing the system's classes, their attributes, operations (or methods), and the rela ...
s and
composite structure diagram
Composite structure diagram in the Unified Modeling Language (UML) is a type of static structure diagram, that shows the internal structure of a class and the ''collaborations'' that this structure makes possible.
This diagram can include intern ...
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
A sequence diagram or system sequence diagram (SSD) shows process interactions arranged in time sequence in the field of software engineering. It depicts the processes involved and the sequence of messages exchanged between the processes needed ...
s,
activity diagram
Activity diagrams are graphical representations of workflows of stepwise activities and actions with support for choice, iteration and concurrency. In the Unified Modeling Language, activity diagrams are intended to model both computational and o ...
s and
state machine diagrams.
UML models can be exchanged among
UML tool
A UML tool is a software application that supports some or all of the notation and semantics associated with the Unified Modeling Language (UML), which is the industry standard general-purpose modeling language for software engineering.
''UML tool ...
s by using the
XML Metadata Interchange
The XML Metadata Interchange (XMI) is an Object Management Group (OMG) standard for exchanging metadata information via Extensible Markup Language (XML).
It can be used for any metadata whose metamodel can be expressed in Meta-Object Facili ...
(XMI) format.
In UML, one of the key tools for behavior modeling is the use-case model, caused by
OOSE
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pro ...
. 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.
Diagrams
UML 2 has many types of diagrams, which are divided into two categories.
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:
![UML diagrams overview](https://upload.wikimedia.org/wikipedia/commons/e/ed/UML_diagrams_overview.svg)
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
Software architecture is the fundamental structure of a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements and relations.
...
of software systems. For example, the
component diagram
In Unified Modeling Language (UML), a component diagram depicts how components are wired together to form larger components or software systems.
They are used to illustrate the structure of arbitrarily complex systems.
Overview
A component diag ...
describes how a software system is split up into components and shows the dependencies among these components.
Policy Admin Component Diagram.PNG, Component diagram
In Unified Modeling Language (UML), a component diagram depicts how components are wired together to form larger components or software systems.
They are used to illustrate the structure of arbitrarily complex systems.
Overview
A component diag ...
BankAccount1.svg, Class diagram
In software engineering, a class diagram in the Unified Modeling Language (UML) is a type of static structure diagram that describes the structure of a system by showing the system's classes, their attributes, operations (or methods), and the rela ...
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
Activity diagrams are graphical representations of workflows of stepwise activities and actions with support for choice, iteration and concurrency. In the Unified Modeling Language, activity diagrams are intended to model both computational and o ...
describes the business and operational step-by-step activities of the components in a system.
Activity conducting.svg, Activity diagram
Activity diagrams are graphical representations of workflows of stepwise activities and actions with support for choice, iteration and concurrency. In the Unified Modeling Language, activity diagrams are intended to model both computational and o ...
UML Use Case diagram.svg, Use case diagram
A use case diagram is a graphical depiction of a user's possible interactions with a system. A use case diagram shows various use cases and different types of users the system has and will often be accompanied by other types of diagrams as well. Th ...
Interaction diagrams
Interaction diagrams, a subset of behavior diagrams, emphasize the
flow of control
In computer science, control flow (or flow of control) is the order in which individual statements, instructions or function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an ''imp ...
and data among the things in the system being modeled. For example, the
sequence diagram
A sequence diagram or system sequence diagram (SSD) shows process interactions arranged in time sequence in the field of software engineering. It depicts the processes involved and the sequence of messages exchanged between the processes needed ...
shows how objects communicate with each other regarding a sequence of messages.
CheckEmail.svg, Sequence diagram
A sequence diagram or system sequence diagram (SSD) shows process interactions arranged in time sequence in the field of software engineering. It depicts the processes involved and the sequence of messages exchanged between the processes needed ...
UML Communication diagram.svg, Communication diagram
A communication diagram in the Unified Modeling Language (UML) 2.0, is a simplified version of the UML 1.x collaboration diagram.
UML has four types of interaction diagrams:
* Sequence diagram
* Communication diagram
* Interaction overview di ...
Metamodeling
![M0-m3](https://upload.wikimedia.org/wikipedia/commons/9/93/M0-m3.png)
The Object Management Group (OMG) has developed a
metamodeling
A metamodel or surrogate model is a model of a model, and metamodeling is the process of generating such metamodels. Thus metamodeling or meta-modeling is the analysis, construction and development of the frames, rules, constraints, models and ...
architecture to define the UML, called the
Meta-Object Facility
The Meta-Object Facility (MOF) is an Object Management Group (OMG) standard for model-driven engineering. Its purpose is to provide a type system for entities in the CORBA architecture and a set of interfaces through which those types can be creat ...
. 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.
The meta-model can be extended using a mechanism called
stereotyping
In social psychology, a stereotype is a generalized belief about a particular category of people. It is an expectation that people might have about every person of a particular group. The type of expectation can vary; it can be, for example ...
. This has been criticized as being insufficient/untenable by
Brian Henderson-Sellers
Brian Henderson-Sellers (born January 1951) is an English computer scientist residing in Sydney, Australia, and Professor of Information Systems at the University of Technology Sydney. He is also Director of the Centre for Object Technology and Ap ...
and Cesar Gonzalez-Perez in "Uses and Abuses of the Stereotype Mechanism in UML 1.x and 2.0".
[B. Henderson-Sellers; C. Gonzalez-Perez (2006). "Uses and Abuses of the Stereotype Mechanism in UML 1.x and 2.0". in: ''Model Driven Engineering Languages and Systems''. Springer Berlin / Heidelberg.]
Adoption
UML has been marketed for many contexts.
It has been treated, at times, as a design
silver bullet
In folklore, a bullet cast from silver is often one of the few weapons that are effective against a werewolf or witch. The term ''silver bullet'' is also a metaphor for a simple, seemingly magical, solution to a difficult problem: for example, pe ...
, 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.
It is considered a large language, with many
constructs. Some people (including
Jacobson) feel that UML's size hinders learning (and therefore, using it).
See also
*
Applications of UML
UML (Unified Modeling Language) is a modeling language used by software developers. UML can be used to develop diagrams and provide users (programmers) with ready-to-use, expressive modeling examples.UML can be applied in areas like embedded sys ...
*
Business Process Model and Notation (BPMN)
*
C4 model The C4 model is a lean graphical notation technique for modelling the architecture of software systems. It is based on a structural decomposition of a system into containers and components and relies on existing modelling techniques such as the Un ...
*
Model-based testing
Model-based testing is an application of model-based design for designing and optionally also executing artifacts to perform software testing or system testing. Models can be used to represent the desired behavior of a system under test (SUT), or ...
*
Model-driven engineering
Model-driven engineering (MDE) is a software development methodology that focuses on creating and exploiting domain models, which are conceptual models of all the topics related to a specific problem. Hence, it highlights and aims at abstract re ...
*
Object Oriented Role Analysis and Modeling The OOram (Object-oriented Role Analysis and Modeling) is a method, based on the concept of ''role'', for performing object-oriented modeling.
(Presented at OOPSLA 1996 Workshop: ''Exploration of Framework Design Principles'')
Originally (1989) co ...
*
Systems Modeling Language (SysML)
*
List of Unified Modeling Language tools
This article compares UML tools. UML tools are software applications which support some functions of the Unified Modeling Language.
General
Features
See also
* List of requirements engineering tools
Requirements engineering tools a ...
*
Department of Defense Architecture Framework
The Department of Defense Architecture Framework (DoDAF) is an architecture framework for the United States Department of Defense (DoD) that provides visualization infrastructure for specific stakeholders concerns through viewpoints organized b ...
*
MODAF
The British Ministry of Defence Architecture Framework (MODAF) was an enterprise architecture framework, architecture framework which defined a standardised way of conducting enterprise architecture, originally developed by the British Ministry ...
*
DOT (graph description language)
DOT is a graph description language. DOT graphs are typically files with the filename extension ''gv'' or ''dot''. The extension ''gv'' is preferred, to avoid confusion with the extension ''dot'' used by versions of Microsoft Word before 2007.
V ...
*
Process Specification Language
The Process Specification Language (PSL) is a set of logic terms used to describe processes. The logic terms are specified in an ontology that provides a formal description of the components and their relationships that make up a process. The o ...
References
Further reading
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External links
*
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