A classifier is a category of Unified Modeling Language

Unified Modeling Language

Unified Modeling Language is a standardized general-purpose modeling language in the field of object-oriented software engineering. The standard is managed, and was created, by the Object Management Group...

 (UML) elements that have some common features, such as attribute

Attribute (computing)

In computing, an attribute is a specification that defines a property of an object, element, or file. It may also refer to or set the specific value for a given instance of such....

s or method

Method (computer science)

In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...

s.

A classifier is an abstract

Abstraction (computer science)

In computer science, abstraction is the process by which data and programs are defined with a representation similar to its pictorial meaning as rooted in the more complex realm of human life and language with their higher need of summarization and categorization , while hiding away the...

 metaclass

Metaclass

In object-oriented programming, a metaclass is a class whose instances are classes. Just as an ordinary class defines the behavior of certain objects, a metaclass defines the behavior of certain classes and their instances. Not all object-oriented programming languages support metaclasses...

 classification concept that serves as a mechanism to show interfaces

Interface (computer science)

In the field of computer science, an interface is a tool and concept that refers to a point of interaction between components, and is applicable at the level of both hardware and software...

, classes

Class (computer science)

In object-oriented programming, a class is a construct that is used as a blueprint to create instances of itself – referred to as class instances, class objects, instance objects or simply objects. A class defines constituent members which enable these class instances to have state and behavior...

, datatypes and components

Component diagram

In the Unified Modeling Language, a component diagram depicts how components are wired together to form larger components and or software systems.They are used to illustrate the structure of arbitrarily complex systems.- Overview :...

.

A classifier describes a set

Set (computer science)

In computer science, a set is an abstract data structure that can store certain values, without any particular order, and no repeated values. It is a computer implementation of the mathematical concept of a finite set...

 of instances that have common behavioral and structural features (operations and attributes

Attribute (computing)

In computing, an attribute is a specification that defines a property of an object, element, or file. It may also refer to or set the specific value for a given instance of such....

, respectively).

A classifier is a namespace

Namespace (computer science)

A namespace is an abstract container or environment created to hold a logical grouping of unique identifiers or symbols . An identifier defined in a namespace is associated only with that namespace. The same identifier can be independently defined in multiple namespaces...

 whose members

Method (computer science)

In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...

 can specify a generalization hierarchy by referencing its general classifiers.

A classifier is a type and can own generalizations, thereby making it possible to define generalization relationships to other classifiers.

A classifier is a redefinable element, as it is possible to redefine nested classifiers.

All objects

Object (computer science)

In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure...

 that can have instances are classifiers.

Important Aspects

• A classifier defines a namespace
  Namespace
  In general, a namespace is a container that provides context for the identifiers it holds, and allows the disambiguation of homonym identifiers residing in different namespaces....
  
  .
• A classifier contains a set of features.
• A classifier is generalizable.

Types of UML Classifiers

• Class
  Class (computer science)
  In object-oriented programming, a class is a construct that is used as a blueprint to create instances of itself – referred to as class instances, class objects, instance objects or simply objects. A class defines constituent members which enable these class instances to have state and behavior...
  
  
• Component
  Component diagram
  In the Unified Modeling Language, a component diagram depicts how components are wired together to form larger components and or software systems.They are used to illustrate the structure of arbitrarily complex systems.- Overview :...
  
  
• Datatype
• Interface
  Interface (computer science)
  In the field of computer science, an interface is a tool and concept that refers to a point of interaction between components, and is applicable at the level of both hardware and software...
  
  
• Node
  Vertex (graph theory)
  In graph theory, a vertex or node is the fundamental unit out of which graphs are formed: an undirected graph consists of a set of vertices and a set of edges , while a directed graph consists of a set of vertices and a set of arcs...
  
  
• Signal
• Subsystem
• Use Case
  Use case
  In software engineering and systems engineering, a use case is a description of steps or actions between a user and a software system which leads the user towards something useful...
  
  

Predefined UML classifiers

• Actor
  Actor (UML)
  An actor in the Unified Modeling Language "specifies a role played by a user or any other system that interacts with the subject.""An Actor models a type of role played by an entity that interacts with the subject ,...
  
  
• Association
  Association (object-oriented programming)
  In object-oriented programming, association defines a relationship between classes of objects that allows one object instance to cause another to perform an action on its behalf...
  
  
• Class
  Class (computer science)
  In object-oriented programming, a class is a construct that is used as a blueprint to create instances of itself – referred to as class instances, class objects, instance objects or simply objects. A class defines constituent members which enable these class instances to have state and behavior...
  
  
• Component
  Component diagram
  In the Unified Modeling Language, a component diagram depicts how components are wired together to form larger components and or software systems.They are used to illustrate the structure of arbitrarily complex systems.- Overview :...
  
  
• Datatype
• Interface
  Interface (computer science)
  In the field of computer science, an interface is a tool and concept that refers to a point of interaction between components, and is applicable at the level of both hardware and software...
  
  
• Node
  Vertex (graph theory)
  In graph theory, a vertex or node is the fundamental unit out of which graphs are formed: an undirected graph consists of a set of vertices and a set of edges , while a directed graph consists of a set of vertices and a set of arcs...
  
  
• Signal
• Subsystem
• Use Case
  Use case
  In software engineering and systems engineering, a use case is a description of steps or actions between a user and a software system which leads the user towards something useful...
  
  

External links

• UML Classifier