Design Philosophy

IDL is built on three foundational commitments that shape every decision in the specification: invariance over convention, composition over inheritance, and machine-readability as a first-class constraint. These are not aesthetic preferences — they are the axioms from which the specification's rules are derived.

Invariance Over Convention

Convention-based design systems rely on shared understanding to maintain consistency. When that understanding diverges — across teams, time, or platforms — inconsistency accumulates silently. IDL replaces convention with invariance: properties that the system declares must remain true are enforced by the compiler, not by agreement. If a spatial value must resolve to a base-unit multiple, the compiler rejects non-conforming values at parse time. The rule does not require interpretation.

Composition Over Inheritance

Inheritance-based systems create implicit dependency graphs that are difficult to audit and fragile to change. A component that inherits token values from a parent propagates changes in ways that are not locally visible. IDL's composition model is explicit: every reference — token to token, slot to component, component to component — is declared. The compiler validates the complete composition graph. No implicit dependency can exist.

Machine-Readability as a First-Class Constraint

IDL is authored by humans but consumed by machines — the compiler, platform emitters, AI systems, CI pipelines. Every structural decision in the specification is evaluated against the question: can this be parsed, validated, and transformed deterministically? Constructs that resist deterministic processing are outside the IDL grammar. This constraint produces a specification that is simultaneously more rigorous for human authors and more useful for automated consumers.