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08 — Source Surfaces, Notation Islands, and Surface Equivalence

Status

  • Normative baseline
  • Version: 0.9.0
  • Layer: Part 0 / Foundation

1. Purpose

This chapter defines the relationship between humane source surfaces, notation islands, and canonical equivalence.

2. Humane Source Surfaces

  • rhoemd is the prose-first humane surface.
  • rhoedsl is the structure-first humane surface.
  • Neither surface is a separate language.
  • Both surfaces are valid only by lowering into the canonical AST.

3. Canonical Serialized Surface

  • RhoeJSON is the machine-neutral serialized surface for interchange and fixtures.
  • It is not the primary authoring surface.

4. Secondary Near-AST Target Surfaces

  • RhoeTypst, RhoeLaTeX, and RhoeHTML are official Part 2 near-AST target-source surfaces.
  • They are emitted and editable target-native contracts.
  • They are not humane source surfaces and they are not part of Part 1 surface-equivalence doctrine.
  • Their host-language grammars remain authoritative for token-level syntax.

5. Notation Islands

  • A notation island is a bounded syntax region hosted inside a primary surface.
  • Notation islands are permitted when:
  • their boundary is explicit
  • they lower into canonical AST structure
  • they do not seize semantic authority from the AST

6. Surface Equivalence

  • Two sources are equivalent if they normalize to the same canonical AST.
  • Deprecated compatibility sources remain equivalent to canonical sources only if their lowering path is explicitly defined.
  • Surface equivalence does not require source-text preservation.
  • Round-trip stability requires semantic preservation, not identical token preservation.

7. Canonical and Compatibility Surfaces

  • Canonical stage surface:
  • :::front-matter
  • :::main-matter
  • :::back-matter
  • :::frameset
  • :::frame
  • :::frame-section
  • :::zone
  • Compatibility stage surface:
  • :::slide
  • :::slide-section
  • %%%
  • %%
  • %
  • Compatibility root metadata alias:
  • shell-grammar: -> composition-grammar:

8. Writer Doctrine

  • Canonical writers MUST emit canonical forms unless strict preservation mode is explicitly requested.
  • Strict preservation MAY retain deprecated spellings in raw-source round-trip tools, but it does not change the canonical AST.
  • Part 2 target writers MAY emit RhoeTypst, RhoeLaTeX, and RhoeHTML, but those emitted surfaces do not participate in Part 1 equivalence claims.