Question

the relatoin "<" is​

Answer 1

Answer:

In knowledge representation, object-oriented programming and design (see object-oriented program architecture), is-a (is_a or is a) is a subsumption[1] relationship between abstractions (e.g. types, classes), wherein one class A is a subclass of another class B (and so B is a superclass of A). In other words, type A is a subtype of type B when A's specification implies B's specification. That is, any object (or class) that satisfies A's specification also satisfies B's specification, because B's specification is weaker.[2]

The is-a relationship is to be contrasted with the has-a (has_a or has a) relationship between types (classes); confusing the relations has-a and is-a is a common error when designing a model (e.g., a computer program) of the real-world relationship between an object and its subordinate. The is-a relationship may also be contrasted with the instance-of relationship between objects (instances) and types (classes): see "type-token distinction" and "type-token relations."[3]

To summarize the relations, there are:

hyperonym–hyponym (supertype–subtype) relations between types (classes) defining a taxonomic hierarchy, where

for a subsumption relation: a hyponym (subtype, subclass) has a type-of (is-a) relationship with its hyperonym (supertype, superclass);

holonym–meronym (whole/entity/container-part/constituent/member) relations between types (classes) defining a possessive hierarchy, where

for an aggregation (i.e. without ownership) relation:

a holonym (whole) has a has-a relationship with its meronym (part),

for a composition (i.e. with ownership) relation:

a meronym (constituent) has a part-of relationship with its holonym (entity),

for a containment[4] relation:

a meronym (member) has a member-of relationship with its holonym (container);

concept-object (type-token) relations between types (classes) and objects (instances), where

a token (object) has an instance-of relationship with its type (class).