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In knowledge representation
Knowledge representation

Knowledge representation is an area in artificial intelligence that is concerned with how to formally "think", that is, how to use a symbol system to represent "a domain of discourse" - that which can be talked about, along with functions that may or may not be within the domain of discourse that allow inference about the objects within the...
 and object-oriented programming
Object-oriented programming

Object-oriented programming is a programming paradigm that uses "Object_" and their interactions to design applications and computer programs....
 and design, is-a is a relationship where one class D is a subclass
Subclass

Subclass may refer to:* Subclass , a taxonomic rank intermediate between class and superorder* Subclass , a class that is derived from another class or classes...
  of another class B (and so B is a superclass
Superclass

Superclass may be:* The global ruling class created by globalization .* Superclass , a book about global governance by David Rothkopf.* Superclass , a taxonomic rank intermediate between subphylum and class....
  of D).

In other words, "D is a B" usually means that concept D is a specialization
Specialization

Specialisation, also spelt specialization, is an important way to generate propositional knowledge, by applying general knowledge, such as the theory of gravity, to specific instances, such as "when I release this apple, it will fall to the floor"....
 of concept B, and concept B is a generalization
Generalization

Generalization is a foundational element of logic and reasoning. Generalization posits the existence of a domain or Set theory of elements, as well as one or more common characteristics shared by those elements....
 of concept D. For instance, a "fruit" is a generalization of "apple", "orange", "mango" and many others.






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In knowledge representation
Knowledge representation

Knowledge representation is an area in artificial intelligence that is concerned with how to formally "think", that is, how to use a symbol system to represent "a domain of discourse" - that which can be talked about, along with functions that may or may not be within the domain of discourse that allow inference about the objects within the...
 and object-oriented programming
Object-oriented programming

Object-oriented programming is a programming paradigm that uses "Object_" and their interactions to design applications and computer programs....
 and design, is-a is a relationship where one class D is a subclass
Subclass

Subclass may refer to:* Subclass , a taxonomic rank intermediate between class and superorder* Subclass , a class that is derived from another class or classes...
  of another class B (and so B is a superclass
Superclass

Superclass may be:* The global ruling class created by globalization .* Superclass , a book about global governance by David Rothkopf.* Superclass , a taxonomic rank intermediate between subphylum and class....
  of D).

In other words, "D is a B" usually means that concept D is a specialization
Specialization

Specialisation, also spelt specialization, is an important way to generate propositional knowledge, by applying general knowledge, such as the theory of gravity, to specific instances, such as "when I release this apple, it will fall to the floor"....
 of concept B, and concept B is a generalization
Generalization

Generalization is a foundational element of logic and reasoning. Generalization posits the existence of a domain or Set theory of elements, as well as one or more common characteristics shared by those elements....
 of concept D. For instance, a "fruit" is a generalization of "apple", "orange", "mango" and many others. One can say that an apple is a fruit.

In object-oriented programming
Object-oriented programming

Object-oriented programming is a programming paradigm that uses "Object_" and their interactions to design applications and computer programs....
 the is-a relationship arises in the context of inheritance
Inheritance (computer science)

In object-oriented programming, inheritance is a way to form new class es using classes that have already been defined. The inheritance concept was invented in 1967 for Simula....
 concept. One can say that "apple" may inherit all the properties common to all fruits, such as being a fleshy container for the seed of a plant.

The is-a relationship is contrasted with the has-a
Has-a

In database design and object oriented program architecture, has-a is a relationship where one object "belongs" to another object , and behaves according to the rules of ownership....
 relationship which constitutes a different kind of hierarchy.

When designing a model (e.g., a computer program
Computer program

Computer programs are Instruction for a computer. A computer requires programs to function. Moreover, a computer program does not run unless its instructions are executed by a Central processing unit; however, a program may communicate an Algorithm#Formalization of algorithms to people without running....
) of the real-world relationship between an object and its subordinate, a common error is confusing the relations has-a and is-a.

See also

  • Has-a
    Has-a

    In database design and object oriented program architecture, has-a is a relationship where one object "belongs" to another object , and behaves according to the rules of ownership....
  • Subsumption
    Subsumption

    Subsumption may refer to:* A minor premise in symbolic logic * The Liskov substitution principle in object-oriented programming* Subsumption architecture in robotics...
  • Inheritance (computer science)
    Inheritance (computer science)

    In object-oriented programming, inheritance is a way to form new class es using classes that have already been defined. The inheritance concept was invented in 1967 for Simula....
  • Subtype
    Subtype

    In computer science, a subtype is a datatype that is generally related to another datatype by some notion of substitutability, meaning that computer programs written to operate on elements of the supertype can also operate on elements of the subtype....
  • Liskov substitution principle
    Liskov substitution principle

    In object-oriented programming, the Liskov substitution principle is a particular definition of subtype that was introduced by Barbara Liskov in a 1987 conference keynote address entitled Data abstraction and hierarchy...
     (in object-oriented programming
    Object-oriented programming

    Object-oriented programming is a programming paradigm that uses "Object_" and their interactions to design applications and computer programs....
    )
  • Hyponym