Object graph: Difference between revisions

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{{short description|Network representation of the relationships between objects in a program}}

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In [[computer science]], in an [[Object-oriented programming|object-oriented program]], groups of [[Object (computer science)|objects]] form a network through their relationships with each other, either through a direct [[Reference (computer science)|reference]] to another object or through a chain of intermediate references. These groups of objects are referred to as '''object graphs''', after the mathematical objects called [[Graph (discrete mathematics)|graphs]] studied in [[graph theory]].

An '''Objectobject graph''' is a view of an [[object system]] at a particular point in time. WhereasUnlike a normal [[data model]] such as a [[Unified Modeling Language|UML]] (UML) [[Classclass diagram]], which details the relationships between [[Class (computer programming)|classes]], the object graph relates their [[Instance (computer science)|instances]]. [[Object diagram]]s are subsets of the overall object graph.

An '''Object graph''' is a view of an object system at a particular point in time. Whereas a normal [[data model]] such as a [[Unified Modeling Language|UML]] [[Class diagram]] details the relationships between classes, the object graph relates their instances. [[Object diagram]]s are subsets of the overall object graph.

Object-oriented applications contain complex webs of interrelated objects. Objects are linked to each other by one object either owning or containing another object or holding a reference to another object. This web of objects is called an object graph and it is the more abstract structure that can be used in discussing an application's state.

==Physical representation==

An object graph is a [[directed graph]], which might be [[Cycle graph|cyclic]]. When stored in [[Random access memory|RAM]], objects occupy different segments of the memory with their attributes and function table, while relationships are represented by [[Pointerpointer (computingcomputer programming)|pointerspointer]]s or a different type of global handler in higher-level languages.

==Examples==

For instance, a Car class can compose a Wheel one. In the object graph a Car instance will have up to four links to its wheels, which can be named frontLeft, frontRight, backLeftback Left and backRightback Right.

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An example of an [[adjacency list]] representation might be something as follows:

For instance, a Car class can compose a Wheel one. In the object graph a Car instance will have up to four links to its wheels, which can be named frontLeft, frontRight, backLeft and backRight.

Example of an [[adjacency list]] representation: c:Car → {frontLeft:Wheel, frontRight:Wheel, backLeft:Wheel, backRight:Wheel}.

c:Car → {front Left:Wheel, front Right:Wheel, back Left:Wheel, back Right:Wheel}.

==See also==

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[[Category:Data modeling diagrams]]