View source for Object (computer science)

{{Short description|Software abstraction with state, behavior, and identity}}

In [[software development]], an '''object''' is an [[entity]] that has [[State (computer science)|state]], [[behavior]], and [[Identity (object-oriented programming)|identity]].<ref name="ooa">{{cite book|title=Object-Oriented Analysis and Design with Applications |edition=3 |date=April 30, 2007 |author1=Grady Booch |author2=Robert Maksimchuk |author3=Michael Engle |author4=Bobbi Young |author5=Jim Conallen |author6=Kelli Houston |isbn=978-0201895513 |publisher= Addison-Wesley Professional}}</ref>{{rp|78}} An object can [[model]] some part of [[reality]] or can be an [[invention]] of the [[design process]] whose collaborations with other such objects serve as the mechanisms that provide some higher-level behavior. Put another way, an object represents an individual, identifiable item, unit, or entity, either real or abstract, with a well-defined role in the problem domain.<ref name="ooa"></ref>{{rp|76}}

A [[programming language]] can be classified based on its support for objects. A language that provides an encapsulation construct for state, behavior, and identity is classified as [[object-based language|object-based]]. If the language also provides [[polymorphism (computer science)|polymorphism]] and [[inheritance (object-oriented programming)|inheritance]] it is classified as [[Object-oriented programming|object-oriented]]. A language that supports creating an object from a [[class (computer science)|class]] is classified as [[class-based programming|class-based]]. A language that supports object creation via a template object is classified as [[prototype-based programming|prototype-based]].

The concept of object is used in many different software contexts, including:

* Possibly the most common use is [[Computer memory|in-memory]] objects in a [[computer program]] written in an object-based language.

* [[Information systems]] can be [[object-oriented analysis and design|modeled]] with objects representing their components and interfaces.<ref name="ooa"/>{{rp|39}}
 
* In the [[relational model]] of [[database]] management, aspects such as [[Table (database)|table]] and [[Column (database)|column]] may act as objects.<ref name=Oppel>{{cite book |first=Andy |last=Oppel |title=SQL Demystified |publisher=McGraw Hill |year=2005| page=7 |isbn=0-07-226224-9}}</ref>

* [[Distributed object|Objects]] of a [[distributed computing]] system tend to be larger grained, longer lasting, and more service-oriented than programming objects.

==See also==
*{{annotated link|Actor model}}
*{{annotated link|Business object}}
*{{annotated link|Instance (computer science)}}
*{{annotated link|Object lifetime}}
*{{annotated link|Object copying}}
*{{annotated link|Semantic Web}}

==References==
{{Reflist}}

==External links==
*[http://java.sun.com/docs/books/tutorial/java/concepts/object.html ''What Is an Object?''] from ''The Java Tutorials''

{{Software engineering}}
{{Data types}}
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[[Category:Object (computer science)| ]]
[[Category:Object-oriented programming]]
[[Category:Data types]]
[[Category:Composite data types]]