Object–role modeling: Difference between revisions

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{{shortShort description|Programming technique}}

{{Distinguish|object–relationalObject–relational mapping}}

{{short description|Programming technique}}

[[File:ORM-diagram-tkz-orm.png|406px|thumb|exampleExample of an ORM2 diagram]]

'''Object-roleObject–role modeling''' ('''ORM''') is used to model the [[semantics]] of a [[universe of discourse]]. ORM is often used for [[data modeling]] and [[software engineering]].

An object-roleobject–role model uses graphical symbols that are based on [[First-order logic|first order predicate logic]] and set theory to enable the modeler to create an unambiguous definition of an arbitrary universe of discourse. Attribute free, the predicates of an ORM Model lend themselves to the analysis and design of [[graph database]] models in as much as ORM was originally conceived to benefit relational database design.

The term "object-roleobject–role model" was coined in the 1970s and ORM based tools have been used for more than 30 years&nbsp;– principally for [[data modeling]]. More recently ORM has been used to model [[business rules]], XML-Schemas, [[data warehouse]]s, requirements engineering and web forms.<ref>{{Cite journalbook | last = Jarrar | first = M. | doititle = 10.1007/978Conceptual Modeling -3-540-75563-0_14 ER 2007 | titlechapter = Towards Automated Reasoning on ORM Schemes | journaldoi = Lecture Notes in Computer Science10. Proceedings of the 26th International Conference on Conceptual Modeling1007/978-3-540-75563-0_14 | series = Lecture Notes in Computer Science | volume = 4801 | pages = 181–197 | year = 2007 | bibcode = 2007LNCS.4801..181J | isbn = 978-3-540-75562-3 | citeseerx = 10.1.1.148.6251 }}</ref>

== History ==

The roots of ORM can be traced to research into semantic modeling for information systems in Europe during the 1970s. There were many pioneers and this short summary does not by any means mention them all. An early contribution came in 1973 when Michael Senko wrote about "data structuring" in the IBM Systems Journal. In 1974 Jean-Raymond Abrial contributed an article about "Data Semantics". In June 1975, [[Eckhard Falkenberg]]'s doctoral thesis was published and in 1976 one of Falkenberg's papers mentions the term "object-roleobject–role model".

[[G.M. Nijssen]] made fundamental contributions by introducing the "circle-box" notation for object types and roles, and by formulating the first version of the conceptual schema design procedure. Robert Meersman extended the approach by adding subtyping, and introducing the first truly conceptual query language.

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In 1989, [[Terry Halpin]] completed his PhD thesis on ORM, providing the first full formalization of the approach and incorporating several extensions.

Also in 1989, [[Terry Halpin]] and [[G.M. Nijssen]] co-authored the book "Conceptual Schema and Relational Database Design" and several joint papers, providing the first formalization of object-roleobject–role modeling.

A graphical NIAM design tool which included the ability to generate database-creation scripts for Oracle, DB2 and DBQ was developed in the early 1990s in Paris. It was originally named Genesys and was marketed successfully in France and later Canada. It could also handle ER diagram design. It was ported to SCO Unix, SunOs, DEC 3151's and Windows 3.0 platforms, and was later migrated to succeeding [[Microsoft]] operating systems, utilising XVT for cross operating system graphical portability. The tool was renamed OORIANE and is currently being used for large data warehouse and SOA projects.

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== Concepts ==

[[File:Object-Role Model Overview.jpg|thumb|240px|right|Overview of object-roleobject–role model notation, Stephen M. Richard (1999).<ref name="SMR99"/>]]

=== Facts ===

Object-roleObject–role models are based on elementary facts, and expressed in [[diagram]]s that can be verbalised into natural language. A fact is a [[proposition]] such as "John Smith was hired on 5 January 1995" or "Mary Jones was hired on 3 March 2010".

With ORM, [[proposition]]s such as these, are abstracted into "fact types" for example "Person was hired on Date" and the individual propositions are regarded as sample data. The difference between a "fact" and an "elementary fact" is that an elementary fact cannot be simplified without loss of meaning. This "fact-based" approach facilitates modeling, transforming, and querying information from any ___domain.<ref name="orm.net">{{Cite web | url=http://www.orm.net/pdf/ORM2_TechReport1.pdf | title=ORM 2 Graphical Notation | access-date=2024-05-19}}</ref>

=== Attribute-free ===

ORM is attribute-free: unlike models in the [[Entity–relationshipentity–relationship model|entity–relationship]] (ER) and [[Unified Modeling Language]] (UML) methods, ORM treats all elementary facts as relationships and so treats decisions for grouping facts into structures (e.g. attribute-based entity types, classes, relation schemes, XML schemas) as implementation concerns irrelevant to semantics. By avoiding attributes, ORM improves semantic stability and enables verbalization into natural language.

=== Fact-based modeling ===

[[Fact-based modellingmodeling]] includes procedures for mapping facts to attribute-based structures, such as those of ER or UML.<ref name="orm.net"/>

Fact-based textual representations are based on formal subsets of native languages. ORM proponents argue that ORM models are easier to understand by people without a technical education. For example, proponents argue that object-roleobject–role models are easier to understand than declarative languages such as [[Object Constraint Language]] (OCL) and other graphical languages such as [[Unified Modeling Language|UML]] class models.<ref name="orm.net"/> Fact-based graphical notations are more expressive than those of ER and [[Unified Modeling Language|UML]]. An object-roleobject–role model can be automatically mapped to relational and deductive databases (such as [[datalog]]).<ref>{{Cite web|url=http://www.ormfoundation.org/files/folders/orm_2010/entry2360.aspx|archive-url=https://web.archive.org/web/20110413060716/http://www.ormfoundation.org/files/folders/orm_2010/entry2360.aspx|url-status=usurped|archive-date=April 13, 2011|title=P:11 Mapping ORM To Datalog - an Overview - The ORM Foundation|website=www.ormfoundation.org|access-date=May 31, 2020}}</ref>

=== ORM 2 graphical notation ===

ORM2 is the latest generation of object-roleobject–role modeling . The main objectives for the ORM 2 graphical notation are:<ref>{{cite web|url=http://www.orm.net/pdf/ORM2.pdf |title=ORM 2 |access-date=April 22, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090219122007/http://orm.net/pdf/ORM2.pdf |archive-date=February 19, 2009 }} Halpin, T. 2005, 'ORM 2', On the Move to Meaningful Internet Systems 2005: OTM 2005 Workshops, eds R. Meersman, Z. Tari, P. Herrero et al., Cyprus. Springer LNCS 3762, pp. 676-87676–87.</ref>

* More compact display of ORM models without compromising clarity

* Improved internationalization (e.g. avoid English language symbols)

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* [[Concept map]]

* [[Conceptual schema]]

* [[Enhanced entity–relationship model]] (EER)

* [[Information flow diagram]]

* [[Ontology double articulation]]

* [[Ontology engineering]]

* [[Relational algebra]]

* [[Three -schema approach]]

== References ==

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== External links ==

{{Commons category|Object role modeling}}

* [http://www.ormfoundation.org The ORM foundation]

* [http://www.orm.net Terry Halpin's ORM site]

* [http://factmodeling.org FactModeling.org dedicated to Fact-Based Modeling]

{{DEFAULTSORT:Object Role Modeling}}