Selfdescribing

Self-describing, or self-descriptive, is an adjective used to describe an object, statement, or system that contains or conveys information about itself. The term is applied in multiple disciplines to indicate that the subject includes data about its own state, structure, or identity.

In linguistics, words that describe themselves are called autological; for example, "short" is short, and "polysyllabic" is polysyllabic. The broader idea also covers sentences and texts that refer to their own content, producing self-referential effects. In literature, metafiction and autobiographical works often foreground their own creation or narration.

In computing and data representation, a self-describing data set includes metadata that defines its schema or structure, allowing interpretation without external documentation. Examples include certain self-describing formats and schemas embedded in data representations. In mathematics, self-descriptive numbers (also called autobiographical numbers) are base-b numbers with b digits such that the i-th digit counts how many times digit i appears. For base 4, 1210 is self-descriptive; in base 10, a standard example is 6210001000.

The concept of self-description engages questions about self-reference, information encoding, and how systems convey meaning about themselves. It appears in philosophy, linguistics, computer science, and mathematics as a useful way to study structure and representation.