In
software
Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work.
...
object-oriented design
Object-oriented design (OOD) is the process of planning a Object-oriented programming, system of interacting objects for the purpose of solving a software problem. It is one approach to software design.
Overview
An Object (computer science), obje ...
, a layer is a group of
classes that have the same set of link-time
module
Module, modular and modularity may refer to the concept of modularity. They may also refer to:
Computing and engineering
* Modular design, the engineering discipline of designing complex devices using separately designed sub-components
* Mo ...
dependencies to other modules. In other words, a layer is a group of reusable
component
Circuit Component may refer to:
•Are devices that perform functions when they are connected in a circuit.
In engineering, science, and technology Generic systems
* System components, an entity with discrete structure, such as an assem ...
s that are
reusable in similar circumstances. In programming languages, the layer distinction is often expressed as "import" dependencies between software modules.
Layers are often arranged in a
tree
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
-form
hierarchy, with dependency relationships as links between the layers. Dependency relationships between layers are often either
inheritance
Inheritance is the practice of receiving private property, titles, debts, entitlements, privileges, rights, and obligations upon the death of an individual. The rules of inheritance differ among societies and have changed over time. Officia ...
,
composition
Composition or Compositions may refer to:
Arts and literature
*Composition (dance), practice and teaching of choreography
*Composition (language), in literature and rhetoric, producing a work in spoken tradition and written discourse, to include v ...
or
aggregation relationships, but other kinds of dependencies can also be used.
Layers is an
architectural pattern described in many books, for example ''Pattern-Oriented Software Architecture''
Pattern-Oriented Software Architecture - A System of Patterns
See also
* Abstraction layer
* Multitier architecture
In software engineering, multitier architecture (often referred to as ''n''-tier architecture) is a client–server architecture in which presentation, application processing and data management functions are physically separated. The most wide ...
* Shearing layers
References
Object-oriented programming
Software design
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