Interface-based programming, also known as interface-based architecture, is an

architectural pattern Software architecture pattern is a reusable, proven solution to a specific, recurring problem focused on architectural design challenges, which can be applied within various architectural styles. Examples Some examples of architectural patte ...

for implementing

modular programming Modular programming is a software design technique that emphasizes separating the functionality of a program into independent, interchangeable modules, such that each contains everything necessary to execute only one aspect or "concern" of the d ...

at the

component Component may refer to: In engineering, science, and technology Generic systems *System components, an entity with discrete structure, such as an assembly or software module, within a system considered at a particular level of analysis * Lumped e ...

level in an

object-oriented programming Object-oriented programming (OOP) is a programming paradigm based on the concept of '' objects''. Objects can contain data (called fields, attributes or properties) and have actions they can perform (called procedures or methods and impl ...

language which does not have a module system. An example of such a language is

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

prior to

Java 9 The Java language has undergone several changes since JDK 1.0 as well as numerous additions of classes and packages to the standard library. Since J2SE 1.4, the evolution of the Java language has been governed by the Java Community P ...

, which lacked the

Java Platform Module System The Java Platform Module System specifies a distribution format for collections of Java code and associated resources. It also specifies a repository for storing these collections, or '' modules'', and identifies how they can be discovered, loaded ...

, a module system at the level of components introduced with

till

Java 8 The Java language has undergone several changes since JDK 1.0 as well as numerous additions of classes and packages to the standard library. Since J2SE 1.4, the evolution of the Java language has been governed by the Java Community P ...

merely had a ''package'' system, but Java software components typically consist of multiple

Java package A Java package organizes Java classes into namespaces, providing a unique namespace for each type it contains. Classes in the same package can access each other's package-private and protected members. In general, a package can contain the fo ...

s and in any case, interface programming can provide advantages over merely using Java packages, even if a component only consists of a single Java package. Interface-based programming defines the application as a collection of components, in which

Application Programming Interface An application programming interface (API) is a connection between computers or between computer programs. It is a type of software Interface (computing), interface, offering a service to other pieces of software. A document or standard that des ...

(API) calls ''between'' components may only be made through abstract interfaces, not concrete classes. Instances of classes will generally be obtained through other interfaces using techniques such as the Factory pattern. This is claimed to increase the ''modularity'' of the application and hence its

maintainability Maintainability is the ease of maintaining or providing maintenance for a functioning product or service. Depending on the field, it can have slightly different meanings. Usage in different fields Engineering In engineering, maintainability ...

. However, some caution is warranted merely splitting an application into arbitrary components communicating via interfaces does not ''in itself'' guarantee low

coupling A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end mo ...

or high cohesion, two other attributes that are commonly regarded as key for maintainability. An interface-based architecture can be used when third parties or indeed separate teams within the same organisation develop additional components or plugins for an established system. The codebase of the

Eclipse IDE Eclipse is an integrated development environment (IDE) used in computer programming. It contains a base workspace and an extensible plug-in system for customizing the environment. It had been the most popular IDE for Java development until 20 ...

is an example of interface-based programming. Eclipse plugin vendors just have to develop components that satisfy the interface specified by the parent application vendor, the Eclipse Foundation. Indeed, in Eclipse, even the original components such as the Java Development Tools are ''themselves'' plugins. This is somewhat like a

mobile phone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This rad ...

manufacturer specifying a mobile charger interface (pin arrangement, expected

direct current Direct current (DC) is one-directional electric current, flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor (material), conductor such as a wire, but can also flow throug ...

voltage, etc.) and both the manufacturer and third parties making their own mobile phone chargers that comply with this standard interface specification.

Software evolution in interface-based programming

The use of

interfaces Interface or interfacing may refer to: Academic journals * ''Interface'' (journal), by the Electrochemical Society * '' Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Linguistics'' * '' Inter ...

to allow disparate teams to collaborate raises the question of how interface changes happen in interface-based programming. The problem is that if an interface is changed, e.g. by adding a new method, old code written to implement the interface will no longer compile and in the case of dynamically loaded or linked plugins, will either fail to load or link, or crash at runtime. There are two basic approaches for dealing with this problem: # a new interface may be developed with additional functionality, which might inherit from the old interface # a

software versioning Software versioning is the process of assigning either unique ''version names'' or unique ''version numbers'' to unique states of computer software. Within a given version number category (e.g., major or minor), these numbers are generally assig ...

policy such a
semantic versioning 2.0
may be communicated to interface implementors, to allow forward-incompatible, or even backward-incompatible, changes in future "major" versions of the platform Both of these approaches have been used in the Java platform.

Design by contract

The publisher of the interfaces generally promises that they will not change the interface in new "minor" versions of the software, and the implementer, by implementing the interface, implies that they have implemented at least the required parts of the interface without any deviation. An interface can therefore be viewed as a "contractual agreement"{{spaced ndash between a provider and a consumer of the interface. If this contract is documented more formally as a software specification, this is an example of

design by contract Design by contract (DbC), also known as contract programming, programming by contract and design-by-contract programming, is an approach for designing software. It prescribes that software designers should define formal, precise and verifiable ...

. However, design by contract ''per se'' does not mandate the use of interfaces for all components.

References

C# Interface Based Development
c-sharpcorner.com
Interface Based Development – The Unified Modeling Language (UML)
devmentor.org
Architecting a large application with interface-based architecture
rhyous.com, 18 October 2011
Understanding Interface-based Programming
Microsoft Developers Network, accessed 16 September 2016 Architectural pattern (computer science)

Software evolution in interface-based programming

Design by contract

See also

References