kif

Knowledge Interchange Format (KIF) is a computer-readable language designed to represent knowledge for interchange among heterogeneous artificial intelligence systems. It was developed in the early 1990s by researchers at Stanford University’s Knowledge Systems Laboratory as a neutral format to encode knowledge bases, rules, and ontologies so different systems could share information.

KIF employs a simple, Lisp-like, parenthesized syntax. Expressions are built from symbols, constants, and function applications. Variables are indicated with a leading question mark (for example, ?x). The language is capable of expressing a broad range of constructs, including relations, functions, and rules, and it provides mechanisms to represent quantified statements. Its design aims to be flexible enough to map to various underlying logics, such as first-order logic.

Semantics in KIF are not tied to a single logic; instead, KIF defines a syntax and conventions that allow knowledge to be exchanged between systems that implement compatible interpretations. As such, KIF functions as an interlingua for knowledge representation, enabling the export and import of knowledge bases, inference rules, and domain ontologies across different reasoning engines and data sources.

Historically, KIF gained prominence in AI as an early standardization effort for knowledge interchange in the 1990s. Although it never achieved universal adoption as a web-era standard, it influenced later discussions and developments in knowledge representation and interoperability. It remains referenced in scholarly literature as an important step in the pursuit of system-to-system knowledge exchange.

See also: Knowledge representation, Interoperability, Ontology, Logic.