MeTTa Specification

# MeTTa Specification **Author:** Alexey Potapov  ·  **Year:** 2021  ·  **Type:** Language specification document **Canonical source:** the full original specification text (Aug 2021) is preserved verbatim at RawData+Publications+MeTTa Specification (card 3750). ## Summary The 2021 **MeTTa Specification** (Alexey Potapov) is the early canonical definition of **MeTTa** ("Meta-Type Talk") — Hyperon's homoiconic, gradually-typed language for representing and transforming knowledge as metagraph expressions. It establishes MeTTa's core model: **atoms and expressions** as the universal representation; **Spaces** as the metagraph memory over which programs operate; **gradual / dependent typing**; and the **pattern-matching, non-deterministic reduction (evaluation) semantics** that drive computation. It also fixes the foundational notation and the basic type system used by later work. ## Relevance to Hyperon This is a **foundational source** for the MeTTa language. It is the early specification that the later operational-semantics formalization (*Meta-MeTTa*, Meredith, Goertzel, Warrell & Vandervorst, 2023) and the production runtimes (Hyperon Experimental reference runtime, PeTTa) build on. It anchors the MeTTa component cards' claims about the language's design intent. ## See also - MeTTa Programming Language Deep Dive — the expert-level technical deep dive. - Hyperon Experimental — the reference (Rust) MeTTa runtime.