Object (computer science)

In software development, an object is an entity that has state, behavior, and identity.^[1]: 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.^[1]: 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. If the language also provides polymorphism and inheritance it is classified as object-oriented. A language that supports creating an object from a class is classified as class-based. A language that supports object creation via a template object is classified as prototype-based.

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

• Possibly the most common use is in-memory objects in a computer program written in an object-based language.

• Information systems can be modeled with objects representing their components and interfaces.^[1]: 39

• In the relational model of database management, aspects such as table and column may act as objects.^[2]

• Objects of a distributed computing system tend to be larger grained, longer lasting, and more service-oriented than programming objects.

• Actor model – Model of concurrent computation
• Business object – Entity within a multi-tiered software application
• Object lifetime – Time period between the creation and destruction of an object-oriented programming instance
• Object copying – Technique in object-oriented programming
• Semantic Web – Extension of the Web to facilitate data exchange

• What Is an Object? from The Java Tutorials