Unified Modeling Language

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In the field of software=20 engineering, the Unified Modeling Language (UML) is a standardized specificatio= n=20 language for object=20 modeling. UML is a general-pu= rpose=20 modeling language that includes a graphical notation used to = create an = abstract=20 model of = a system, = referred to=20 as a UML=20 model.

UML is officially defined at the Object = Management=20 Group (OMG) by the UML=20 metamodel, a Meta-Object=20 Facility metamodel (MOF). Like other MOF-based specifications, the = UML=20 metamodel and UML models may be serialized in XMI. UML was designed to = specify,=20 visualize, construct, and document software-intensive = systems.

UML is not restricted to modeling software. UML is also used for business = process=20 modeling, systems = engineering=20 modeling, and representing organizati= onal=20 structures. The Systems = Modeling=20 Language (SysML) is a Domain-Spe= cific=20 Modeling language for systems engineering that is defined as a UML = 2.0=20 profile.

UML has been a catalyst for the evolution of model-driven = technologies, which=20 include Model Driven Development (MDD), Model = Driven=20 Engineering (MDE), and Model = Driven=20 Architecture (MDA). By establishing an industry consensus on a = graphic=20 notation to represent common concepts like classes, components, = generalization,=20 aggregation, and behaviors, UML has allowed software developers to = concentrate=20 more on design and architecture.

UML models may be automatically transformed to other representations = (e.g.=20 Java) by means of QVT-like transformation = languages,=20 supported by the OMG.

UML is extensible,=20 offering the following mechanisms for customization: profiles and = stereoty= pe.=20 The semantics of = extension by=20 profiles has been improved with the UML 2.0 major revision.

<= SPAN=20 class=3Dtocnumber>1 History=20
<= SPAN=20 class=3Dtocnumber>2 Methods=20
= 3 Modeling=20
= 4 Diagrams=20
= 5 Concepts=20
6 Criticisms=20
7 Extensions=20
= 8 See = also=20
9 Notes=20
10 References=20
11 External = links=20

[edit]=20 History

After Rational = Software=20 Corporation hired James Rumbaugh = from General = Electric in=20 1994, the company became the source for the two most popular object-oriented= modeling=20 approaches of the day: Rumbaugh's OMT, = which was=20 better for object-ori= ented=20 analysis (OOA), and Grady Booch's Booch=20 method, which was better for object-orien= ted=20 design (OOD). Together Rumbaugh and Booch attempted to reconcile = their two=20 approaches and started work on a Unified Method.

They were soon assisted in their efforts by Ivar Jacobson, = the creator=20 of the OOSE=20 method. Jacobson joined Rational in 1995, after his company, Objectory, = was=20 acquired by Rational. The three methodologists were collectively = referred to as=20 the Three Amigos, since they were well known to argue frequently = with=20 each other regarding methodological preferences.

In 1996 Rational concluded that the abundance of modeling languages = was=20 slowing the adoption of object technology, so repositioning the work on = a=20 Unified Method, they tasked the Three Amigos with the development of a = non-proprietary = Unified=20 Modeling Language. Representatives of competing Object Technology = companies were=20 consulted during OOPSLA '96, and were = won over by=20 Rumbaugh's a cappella = rendition of his=20 version of Joni Mitchell's "Clouds". (Indicating the victory of his OMT = notation=20 of using boxes for representing classes over Grady Booch's Booch=20 method's notation which used cloud symbols).

Under the technical leadership of the Three Amigos, an international=20 consortium called the UML Partners was = organized=20 in 1996 to complete the Unified Modeling Language (UML) = specification,=20 and propose it as a response to the OMG RFP. The UML Partners' UML 1.0=20 specification draft was proposed to the OMG in January 1997. During the = same=20 month the UML Partners formed a Semantics Task Force, chaired by Cris=20 Kobryn and administered by Ed=20 Eykholt, to finalize the semantics of the specification and = integrate it=20 with other standardization efforts. The result of this work, UML 1.1, = was=20 submitted to the OMG in August 1997 and adopted by the OMG in November = 1997.[= 1]

As a modeling notation, the influence of the OMT notation dominates = (e.g.,=20 using rectangles for classes and objects). Though the Booch "cloud" = notation was=20 dropped, the Booch capability to specify lower-level design detail was = embraced.=20 The use=20 case notation from Objectory and the component = notation=20 from Booch were integrated with the rest of the notation, but the = semantic=20 integration was relatively weak in UML 1.1, and was not really fixed = until the=20 UML 2.0 major revision.

Concepts from many other OO methods were also loosely integrated with = UML=20 with the intent that UML would support all OO methods. For example CRC=20 Cards (circa 1989 from Kent Beck and Ward=20 Cunningham), and OORam=20 were retained. Many others contributed too with their approaches = flavoring the=20 many models of the day including: Tony Wasserman and Peter Pircher with = the=20 "Object-Oriented Structured Design (OOSD)" notation (not a method), Ray = Buhr's=20 "Systems Design with Ada", Archie Bowen's use case and timing analysis, = Paul=20 Ward's data analysis and David Hurrel's "Statecharts". as the group = tried to=20 ensure broad coverage in the real-time systems domain. As a result, UML = is=20 useful in a variety of engineering problems, from single process, single = user=20 applications to concurrent, distributed systems, making UML rich but = large.

The Unified Modeling Language is an international standard:

ISO/IEC=20 19501:2005 Information technology -- Open Distributed Processing -- = Unified=20 Modeling Language (UML) Version 1.4.2.

UML has matured significantly since UML 1.1. Several minor revisions = (UML=20 1.3, 1.4, and 1.5) fixed shortcomings and bugs with the first version of = UML,=20 followed by the UML 2.0 major revision, which is the current OMG = standard.

The first part of UML 2.0, the Superstructure which describes the new = diagrams and modeling elements available, was adopted by the OMG in = October=20 2004. Other parts of UML 2, notably the infrastructure, the Object = Constraint=20 Language (OCL) and the diagram interchange were yet to be completed = and=20 ratified as of November 2005.

The final UML 2.0=20 specification has been declared available and has been added = to OMG's=20 formal specification library. The other parts of the UML specification, = the UML = 2.0=20 infrastructure, the UML = 2.0 Diagram=20 Interchange, and UML = 2.0 OCL=20 specifications have been adopted.

UML version 2.1 revision is being developed, and should be available = in the=20 form of an XMI 2.1 version of the UML 2.1 version. The corresponding XMI = 2.1=20 file will be made available from the OMG ADTF group.

Most of the commercially successful UML tools now support = most of=20 UML 2.0, leaving only the rarely used features left to implement. Of = course, it=20 will take some time for the tools that are in the hands of the = developers to=20 reach this level of compliance.

[edit]=20 Methods

UML is not a method by itself; however, it was designed to be = compatible with=20 the leading object-oriented software development methods of its time = (for=20 example OMT, Booch, Objectory). Since UML has evolved, some of these = methods=20 have been recast to take advantage of the new notation (for example = OMT), and=20 new methods have been created based on UML. The best known is Rational = Unified=20 Process (RUP). There are many other UML-based methods like Abstraction=20 Method, = Dynamic=20 Systems Development Method, and others, designed to provide more = specific=20 solutions, or achieve different objectives.

[edit]=20 Modeling

It is very important to distinguish between the UML model and the set = of=20 diagrams of a system. A diagram is a partial graphical representation of = a=20 system's model. The model also contains a "semantic backplane" =E2=80=94 = documentation=20 such as written use cases that drive the model elements and = diagrams.

There are three prominent parts of a system's model:

Functional model

Showcases the functionality of the system from the user's point of = view.=20

Includes use case = diagrams.=20

Object model

Showcases the structure and substructure of the system using = objects,=20 attributes, operations, and relationships.=20

Includes class = diagrams.

Dynamic model

Showcases the internal behavior of the system.=20

Includes sequence = diagrams, activity = diagrams and=20 sta= te=20 machine diagrams.

Models can be exchanged among UML tools by using = the XMI = format.

[edit]=20 Diagrams

In UML 2.0 there are 13 types of diagrams.= To=20 understand them, it can be useful to categorize them hierarchically, as = shown in=20 the hierarchy chart on the right.

Structure diagrams emphasize what things must be in the system = being=20 modeled:

Behavior diagrams emphasize what must happen in the system = being=20 modeled:

Interaction diagrams, a subset of behavior diagrams, emphasize = the=20 flow of control and data among the things in the system being = modeled:

Communication= =20 diagram=20
Interaction=20 overview diagram (UML 2.0)=20
Sequence = diagram=20
UML Timing=20 Diagram (UML 2.0)

The Protocol=20 State Machine is a sub-variant of the State Machine. It may be used = to model=20 network communication protocols.

UML does not restrict UML element types to a certain diagram type. In = general, every UML element may appear on almost all types of diagrams. = This=20 flexibility has been partially restricted in UML 2.0.

Diagrams can be exchanged among UML tools by XMI (also DI, = XMI[DI]).

In keeping with the tradition of engineering drawings, a comment or = note=20 explaining usage, constraint, or intent is always allowed in a UML = diagram.

[edit]=20 Concepts

UML uses many concepts from many sources. For a definitive list, = consult the=20 glossary=20 of Unified Modeling Language terms. Notable concepts are listed = here.

For structure

Actor, attribute,=20 class<= /A>, component, = in= terface,=20 objec= t,=20 pack= age.=20

For behavior

Activity, = event, message, metho= d,=20 operati= on,=20 state<= /A>, use = case.=20

For relationships

Aggregation,=20 association,=20 composition,= dep= ends,=20 generalization = (or = inheritance).=20

Other concepts

Stereoty= pe.=20 It qualifies the symbol it is attached to.=20
Multipli= city=20 notation which corresponds to Database modeling cardinality, = e.g., 1,=20 0..1, 1..*=20
Role=20

[edit]=20 Criticisms

Although UML is a widely recognized and used modeling standard, it is = frequently criticized for the following deficiencies:

Language bloat. = UML is often=20 criticized as being gratuitously large and complex. It contains many = diagrams=20 and constructs that are redundant or infrequently used. This criticism = is more=20 frequently directed at UML 2.0 than UML 1.0, since newer revisions = include=20 more design-by-commi= ttee=20 compromises.=20
Imprecise semantics. = Since UML is=20 specified by a combination of itself (abstract syntax), OCL = (well-formedness rules) and English (detailed semantic), it lacks the = rigor of=20 a language precisely defined using formal = language=20 techniques. In some cases, the UML abstract syntax, OCL and English = are=20 contradictory, in other cases they are incomplete. The imprecision of = the UML=20 specification has consequences for users and tool vendors alike, such = as=20 causing incompatibilities among tools due to unique interpretations of = specs.=20
Problems in learning and adopting. The problems cited above = make=20 learning and adopting UML problematic, especially when management = forces UML=20 upon engineers lacking the prerequisite skills. (See the ACM=20 article for an amusing account of such issues.) =
Only the code is in sync with the code. Another perspective = holds=20 that it is working systems that are important, not beautiful models. = As Jack=20 Reeves succinctly put it, "The code is the design." [1][2] Pursuing this notion leads to the need for = better ways of=20 writing software; UML has value in approaches that compile = the=20 models to generate source or executable code. This however, = may still=20 not be sufficient since UML as a language does not exhibit Turing=20 completeness, and any generated source or executable code would be = limited=20 to what a UML interpreting tool can discern or assume.=20
Cumulative Impedance/Impedance mismatch. As with any = notational=20 system, UML is able to represent some systems more concisely or = efficiently=20 than others. Thus a developer is influenced toward solutions that most = comfortably inhabit the intersection of the strengths between UML and = the=20 coding language. This problem is particularly pronounced if the coding = implementation language does not adhere to orthodox object-oriented = doctrine.=20
Tries to be all things to all people. UML is a general = purpose=20 modeling language, which tries to achieve compatibility with every = possible=20 implementation language. In the context of a specific project, the = most=20 applicable features of UML must be delimited for use by the design = team to=20 accomplish the specific goal. Additionally, the means of restricting = the scope=20 of UML to a particular domain is through a formalism that is not = completely=20 formed, and is itself the subject of criticism.

A paper by professor Brian Henderson-Sellers= at=20 the MoDELS/UML conference in Genova, Italy, October 2006 = details flaws=20 in the definition of the UML 2.0 language.

[edit]=20 Extensions

When it is necessary to introduce new notations or terminologies, UML = provides user-defined extensions through the use of stereotypes, tagged = values=20 and constraints. Currently there are two extensions defined, namely = Business and=20 Objectory Process extensions.

Magnus Penker and Hans-Erik Eriksson (2000) describe Business = Extensions=20 in Business Modeling with UML.=20
Ovidiu S. Noran at the Griffith=20 University compares UML and IDEF in "Business = Modelling: UML=20 vs. IDEF". [3]=20
Peter Coad et al. (1999) have also suggested a small set of = UML=20 colors.=20
Scott Ambler has done extensive work defining how to data model with the UML.

[edit]=20 See also

Agile = Modeling - A=20 modeling method similar to agile = programming=20
Entity-re= lationship=20 model (ER)=20
Executable = UML=20
Generi= c=20 Modeling Environment - GME, a modeling framework=20
List of UML = tools=20
Meta-modeling=20
Model-based=20 testing (MBT)=20
Model=20 Integrated Computing (MIC)=20
Software = blueprint=20
UML Virtual=20 Machine=20
UN/CEFACT's=20 Modeling Methodology (UMM)

[edit]=20 Notes

^<= /A>=20 UML = Specification=20 v. 1.1 (OMG document ad/97-08-11)

[edit]=20 References

Ambler, Scott William (2004). The=20 Object Primer: Agile Model Driven Development with UML 2. = Cambridge=20 University Press. ISBN=20 0-521-54018-6. =20
Chonoles, Michael Jesse; James A. Schardt = (2003).=20 UML 2 for Dummies. Wiley Publishing. ISBN=20 0-7645-2614-6. =20
Coad,=20 Peter; Eric Lefebvre; Jeff De Luca (1999). Java Modeling In Color = With UML:=20 Enterprise Components and Process. Prentice Hall. ISBN=20 0-13-011510-X. <= /SPAN>=20
Fowler, = Martin. UML=20 Distilled: A Brief Guide to the Standard Object Modeling Language, = 3rd=20 ed., Addison-Wesley. ISBN=20 0-321-19368-7. =20
Gooch, Tom. History of UML. Retrieved on 2005-12-28.=20
Jacobson, = Ivar; Grady=20 Booch; James Rumbaugh (1998). The Unified Software Development = Process.=20 Addison Wesley Longman. ISBN=20 0-201-57169-2. =20
Martin,=20 Robert Cecil (2003). UML for Java Programmers. Prentice = Hall. ISBN=20 0-13-142848-9. =20
Noran, Ovidiu S.. Business Modelling: UML vs. IDEF (PDF). Retrieved = on 2005-12-28.=20

Penker, Magnus; Hans-Erik Eriksson = (2000).=20 Business Modeling with UML. John Wiley & Sons. ISBN=20 0-471-29551-5. =20

Henderson Sellers, Brian (2006). about = UML=20 profiles. Springer Verlag. MoDELS'2006 Conference, = Genova. =20

[edit]=20 External links

Database modeling in UML from Methods & Tools (article)=20
Death by UML Fever on the occasional misuse of UML, = from ACM Queue = (article)=20
Dia Modeling = Software Dia is=20 a GTK+ based diagram creation program for Linux, Unix and Windows = released=20 under the GPL license.=20
Introduction to the Diagrams of UML 2=20
OCUP Exam=20 Program at OMG=20
Open source UML editors lag proprietary leader, by = Irfan=20 Habib (article)=20
Practical UML=E2=84=A2: A Hands-On Introduction for = Developers =E2=80=93 a=20 quick introduction to the UML by Randy=20 Miller=20
UML 3.0 and the Future of Modeling, by Cris Kobryn = (article)=20
UML articles directory=20
UML Forum A = virtual=20 community and knowledge portal for modelers interested in UML and its=20 applications.=20
UML = Reference Card=20
UML Resource Page of = the Object = Management=20 Group =E2=80=93 contains the UML specification=20
UMLWiki.org: a Wiki = specializing=20 in UML=20
What Is UML?: an overview of UML and its = applications for=20 managers=20
UML Basics=20
NetBeans UML = Tools - Free,=20 open-source tools for UML modeling, code generation, and reverse = engineering=20

This article was originally = based on=20 material from the Free=20 On-line Dictionary of Computing, which is licensed under=20 the GFDL= .

Retrieved from "http://en= .wikipedia.org/wiki/Unified_Modeling_Language"

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