In programming, the rule of least power is a design principle that "suggests choosing the least powerful omputerlanguage suitable for a given purpose". Stated alternatively, given a choice among computer languages, classes of which range from descriptive (or ''declarative'') to procedural, the less procedural, more descriptive the language one chooses, the more one can do with the data stored in that language. This rule is an application of the

principle of least privilege In information security, computer science, and other fields, the principle of least privilege (PoLP), also known as the principle of minimal privilege (PoMP) or the principle of least authority (PoLA), requires that in a particular abstraction l ...

to protocol design. The Rule of Least Power is an example in context of the centuries older principle known as

Occam's razor In philosophy, Occam's razor (also spelled Ockham's razor or Ocham's razor; ) is the problem-solving principle that recommends searching for explanations constructed with the smallest possible set of elements. It is also known as the principle o ...

in philosophy. In particular, arguments for and against the Rule of Least Power are subject to the same analysis as for

Rationale

Originally proposed as an

axiom An axiom, postulate, or assumption is a statement that is taken to be true, to serve as a premise or starting point for further reasoning and arguments. The word comes from the Ancient Greek word (), meaning 'that which is thought worthy or ...

of good design, the term is an extension of the

KISS principle KISS, an acronym for "Keep it simple, stupid!", is a design principle first noted by the U.S. Navy in 1960. First seen partly in American English by at least 1938, KISS implies that simplicity should be a design goal. The phrase has been associate ...

applied to choosing among a range of languages ranging from * the plainly descriptive ones (such as the content of most

database In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and a ...

s, or progressive enhancement on the web), * logical languages of limited

propositional logic The propositional calculus is a branch of logic. It is also called propositional logic, statement logic, sentential calculus, sentential logic, or sometimes zeroth-order logic. Sometimes, it is called ''first-order'' propositional logic to contra ...

(such as

access control list In computer security, an access-control list (ACL) is a list of permissions associated with a system resource (object or facility). An ACL specifies which users or system processes are granted access to resources, as well as what operations are ...

s), *

declarative language In computer science, declarative programming is a programming paradigm—a style of building the structure and elements of computer programs—that expresses the logic of a computation without describing its control flow. Many languages that app ...

s on the verge of being

Turing-complete In computability theory, a system of data-manipulation rules (such as a model of computation, a computer's instruction set, a programming language, or a cellular automaton) is said to be Turing-complete or computationally universal if it can be ...

, * those that are in fact Turing-complete though one is led not to use them that way (

XSLT XSLT (Extensible Stylesheet Language Transformations) is a language originally designed for transforming XML documents into other XML documents, or other formats such as HTML for web pages, plain text, or XSL Formatting Objects. These formats c ...

, SQL), * those that are functional and Turing-complete

general-purpose programming language In computer software, a general-purpose programming language (GPL) is a programming language for building software in a wide variety of application Domain (software engineering), domains. Conversely, a Domain-specific language, domain-specific pro ...

s, to * those that are "unashamedly imperative". As explained by

Tim Berners-Lee Sir Timothy John Berners-Lee (born 8 June 1955), also known as TimBL, is an English computer scientist best known as the inventor of the World Wide Web, the HTML markup language, the URL system, and HTTP. He is a professorial research fellow a ...

Computer Science in the 1960s to 80s spent a lot of effort making languages that were as powerful as possible. Nowadays we have to appreciate the reasons for picking not the most powerful solution but the least powerful. The reason for this is that the less powerful the language, the more you can do with the data stored in that language. If you write it in a simple declarative form, anyone can write a program to analyze it in many ways. The
Semantic Web The Semantic Web, sometimes known as Web 3.0, is an extension of the World Wide Web through standards set by the World Wide Web Consortium (W3C). The goal of the Semantic Web is to make Internet data machine-readable. To enable the encoding o ...
is an attempt, largely, to map large quantities of existing data onto a common language so that the data can be analyzed in ways never dreamed of by its creators. If, for example, a web page with weather data has RDF describing that data, a user can retrieve it as a table, perhaps average it, plot it, deduce things from it in combination with other information. At the other end of the scale is the weather information portrayed by the cunning Java applet. While this might allow a very cool user interface, it cannot be analyzed at all. The search engine finding the page will have no idea of what the data is or what it is about. The only way to find out what a Java applet means is to set it running in front of a person.

References

The Rule of Least Power

W3C The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in ...

, TAG Finding 23 February 2006 * B. Carpenter, Editor: "Architectural Principles of the Internet" Internet Architecture Board, June 1996, RFC 1958 {{refend Software development philosophies Software design Programming language folklore Software engineering folklore

Rationale

See also

References