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In philosophy and the arts, a fundamental distinction exists between abstract and concrete entities. While there is no universally accepted definition, common examples illustrate the difference: numbers, sets, and ideas are typically classified as abstract objects, whereas plants, dogs, and planets are considered concrete objects.
Each object and link on an object diagram is represented by an InstanceSpecification. This can show an object's classifier (e.g. an abstract or concrete class) and instance name, as well as attributes and other structural features using slots. Each slot corresponds to a single attribute or feature, and may include a value for that entity.
In mathematics, a category (sometimes called an abstract category to distinguish it from a concrete category) is a collection of "objects" that are linked by "arrows". A category has two basic properties: the ability to compose the arrows associatively and the existence of an identity arrow for each object.
Each level uses a system of expression involving a unique set of objects and compositions that apply only to a particular domain. [12] Each relatively abstract, "higher" level builds on a relatively concrete, "lower" level, which tends to provide an increasingly "granular" representation. For example, gates build on electronic circuits, binary ...
[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 ...
In mathematics, the idea of a free object is one of the basic concepts of abstract algebra.Informally, a free object over a set A can be thought of as being a "generic" algebraic structure over A: the only equations that hold between elements of the free object are those that follow from the defining axioms of the algebraic structure.
A concrete category is a pair (C,U) such that . C is a category, and; U : C → Set (the category of sets and functions) is a faithful functor.; The functor U is to be thought of as a forgetful functor, which assigns to every object of C its "underlying set", and to every morphism in C its "underlying function".
In class-based object-oriented programming, abstract types are implemented as abstract classes (also known as abstract base classes), and concrete types as concrete classes. In generic programming , the analogous notion is a concept , which similarly specifies syntax and semantics, but does not require a subtype relationship: two unrelated ...