Unified Modeling Language
In 1997 it was adopted by the Object Management Group (OMG), and has been managed by this organization ever since. In 2000 the Unified Modeling Language was accepted by the International Organization for Standardization (ISO) as an approved standard. Since then it has been revised to cover the latest revision of UML.
- 1 Overview
- 2 History
- 3 Design/Usage
- 4 Adoption
- 5 Criticisms
- 6 See also
- 7 References
- 8 Further reading
- 9 External links
The Unified Modeling Language (UML) offers a way to visualize a system's architectural blueprints in a diagram (see image), including elements such as:
- Any activities (jobs)
- Individual components of the system
- And how they can interact with other software components.
- How the system will run
- How entities interact with others (components and interfaces)
- External user interface
- How the system is expected to be used.
Although originally intended solely for object-oriented design documentation, the Unified Modeling Language (UML) has been extended to cover a larger set of design documentation (as listed above), and been found useful in many contexts.
UML has been evolving since the second half of the 1990s and has its roots in the object-oriented 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.
Before UML 1.x
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: 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.
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 Open Modeling Group (OMG) for standardisation. The partnership was also contained additional interested parties (for example HP, 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.
The 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 process" version and has yet to become formally released.
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
The current versions of these standards follow: UML Superstructure version 2.4.1, UML Infrastructure version 2.4.1, OCL version 2.3.1, and UML Diagram Interchange version 1.0. It continues to be updated and improved by the revision task force, who resolve any issues with the language.
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, Objectory).
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 model also contains 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. The structural view includes class diagrams and composite structure diagrams.
- 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 diagrams, activity diagrams and state machine diagrams.
UML models can be exchanged among UML tools by using the XML Metadata Interchange (XMI) interchange format.
|Structural UML diagrams|
|Behavioral UML 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:
These diagrams may all contain comments or notes explaining usage, constraint, or intent.
Structure diagrams emphasize 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 which describes how a software system is split up into components and shows the dependencies among these components.
Behavior diagrams emphasize 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 it describes the business and operational step-by-step activities of the components in a system.
Interaction diagrams, a subset of behavior diagrams, emphasize the flow of control and data among the things in the system being modeled. For example, the sequence diagram which shows how objects communicate with each other in terms of a sequence of messages.
The Object Management Group (OMG) has developed a metamodeling architecture to define the Unified Modeling Language (UML), called the Meta-Object Facility (MOF). The Meta-Object Facility is designed as a four-layered architecture, as shown in the image at right. It provides a meta-meta model at the top layer, 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, the model that 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. This has been criticised 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".
It has been treated, at times, as a design silver bullet, which has led to problems in its usage. Misuse of it includes excessive usage of it (design every little part of the system's code with it, which is unnecessary) and assuming that anyone can design anything with it (even those who haven't programmed).
It is seen to be a large language, with many constructs in it. Some feel (including Jacobson) that there are too many and that this hinders the learning (and therefore usage) of it. Efforts are underway to attempt to shrink to the size of the language that needs to be learnt. 
||This article's Criticism or Controversy section may compromise the article's neutral point of view of the subject. (December 2010)|
Critique of UML 1.x
- Linguistic incoherence
- The standards have been cited 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, even though several authors (Merise, Elmasri & Navathe  amongst others ) prefer same-side or "look-here" for roles and both minimum and maximum cardinalities. Recent researchers (Feinerer, Dullea et. alia ) 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 >2.
- In Feinerer it 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." (Although the "reduction" mentioned is spurious as the two diagrams 3.4 and 3.5 are in fact the same) and also "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."
- Unified Modeling Language User Guide, The (2 ed.). Addison-Wesley. 2005. p. 496. ISBN 0321267974. , See the sample content, look for history
- Marc Hamilton (1999) Software Development: A Guide to Building Reliable Systems p.48
- "ISO/IEC 19505-1:2012 - Information technology - Object Management Group Unified Modeling Language (OMG UML) - Part 1: Infrastructure". Iso.org. 2012-04-20. Retrieved 2014-04-10.
- "OMG Unified Modeling Language (OMG UML), Superstructure. Version 2.4.1". Object Management Group. Retrieved 09 April 2014.
- Satish Mishra (1997). "Visual Modeling & Unified Modeling Language (UML) : Introduction to UML". Rational Software Corporation. Accessed 9 November 2008.
- "UML, Success Stories". Retrieved 09 April 2014.
- Andreas Zendler (1997) Advanced Concepts, Life Cycle Models and Tools for Objeckt-Oriented Software Development. p.122
- "UML Specification version 1.1 (OMG document ad/97-08-11)". Omg.org. Retrieved 2011-09-22.
- "UML". Omg.org. Retrieved 2014-04-10.
- "UML 2.0". Omg.org. Retrieved 2011-09-22.
- "UML". Omg.org. Retrieved 2011-09-22.
- "UML". Omg.org. Retrieved 2012-02-21.
- "UML". Omg.org. Retrieved 2013-08-07.
- OMG. "Catalog of OMG Modeling and Metadata Specifications". Retrieved 2012-02-21.
- "Issues for UML 2.6 Revision task Force mailing list". Omg.org. Retrieved 2014-04-10.
- John Hunt (2000). The Unified Process for Practitioners: Object-oriented Design, UML and Java. Springer, 2000. ISBN 1-85233-275-1. p.5.door
- Jon Holt Institution of Electrical Engineers (2004). UML for Systems Engineering: Watching the Wheels IET, 2004, ISBN 0-86341-354-4. p.58
- Iman Poernomo (2006) "The Meta-Object Facility Typed" in: Proceeding SAC '06 Proceedings of the 2006 ACM symposium on Applied computing. pp. 1845-1849
- "UML 2.4.1 Infrastructure". Omg.org. 2011-08-05. Retrieved 2014-04-10.
- 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.
- "UML, Success Stories". Retrieved 09 April 2014.
- "UML 2.5: Do you even care?". "UML truly is ubiquitous"
- "Death by UML Fever".
- "Ivar Jacobson on UML, MDA, and the future of methodologies".
- "The Road Ahead for UML | Dr Dobb's".
- Génova et alia 2004 "Open Issues in Industrial Use Case Modeling"
- "Will UML 2.0 Be Agile or Awkward?" (PDF). Retrieved 2011-09-22.
- Hubert Tardieu, Arnold Rochfeld and René Colletti La methode MERISE: Principes et outils (Paperback - 1983)
- Elmasri, Ramez, B. Shamkant, Navathe, Fundamentals of Database Systems, third ed., Addison-Wesley, Menlo Park, CA, USA, 2000.
- ER 2004 : 23rd International Conference on Conceptual Modeling, Shanghai, China, 8-12 November 2004[dead link]
- "A Formal Treatment of UML Class Diagrams as an Efficient Method for Configuration Management 2007" (PDF). Retrieved 2011-09-22.
- "James Dullea, Il-Yeol Song, Ioanna Lamprou - An analysis of structural validity in entity-relationship modeling 2002" (PDF). Retrieved 2011-09-22.
- ""Reasoning about participation constraints and Chen's constraints" S Hartmann - 2003" (PDF). Retrieved 2013-08-17.
- Ambler, Scott William (2004). The Object Primer: Agile Model Driven Development with UML 2. Cambridge University Press. ISBN 0-521-54018-6.
- Chonoles, Michael Jesse; James A. Schardt (2003). UML 2 for Dummies. Wiley Publishing. ISBN 0-7645-2614-6.
- Fowler, Martin. UML Distilled: A Brief Guide to the Standard Object Modeling Language (3rd ed.). Addison-Wesley. ISBN 0-321-19368-7.
- Jacobson, Ivar; Grady Booch; James Rumbaugh (1998). The Unified Software Development Process. Addison Wesley Longman. ISBN 0-201-57169-2.
- Martin, Robert Cecil (2003). UML for Java Programmers. Prentice Hall. ISBN 0-13-142848-9.
- Noran, Ovidiu S. "Business Modelling: UML vs. IDEF" (PDF). Retrieved 2005-12-28.
- Penker, Magnus; Hans-Erik Eriksson (2000). Business Modeling with UML. John Wiley & Sons. ISBN 0-471-29551-5.
|Wikiversity has learning materials about UML|
|Wikimedia Commons has media related to Unified Modeling Language.|
- Official website
- UML Resource Page of the Object Management Group – Resources that include the latest version of the UML specification from the group in charge of defining the UML specification