Extending

Controlled Language Scope

Why multilingual uses controlled language subsets and what this means for language design.

multilingual uses controlled natural language (CNL) subsets, not unconstrained natural language.

Why Controlled Language?

Natural language introduces:

  • Ambiguity — the same word can have multiple meanings
  • Morphology — inflected forms (verb conjugations, plurals, case endings)
  • Cultural variability — idioms, register, context-dependent meaning
  • Synonymy — many words for the same concept

To keep compilation deterministic, each frontend supports a constrained surface. This means:

  • Every token maps to exactly one concept
  • No disambiguation heuristics at parse time
  • No morphological analysis required
  • Predictable behavior for every program

What’s In Scope

Concept-Keyword Mappings

Each semantic concept maps to exactly one keyword per language:

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COND_IF → "if" (en) / "si" (fr) / "wenn" (de) / "もし" (ja) / "إذا" (ar)

One keyword per concept per language. No synonyms, no variants (except diacritic aliases).

Finite Built-in Alias Sets

Localized aliases for a curated set of built-in functions:

  • 41 concepts currently localized
  • Each maps to exactly one alias per language
  • Universal English names always available alongside aliases

Finite Declarative Surface Normalization Patterns

For SOV/RTL languages, declarative rules handle alternate word orders:

  • Rules are finite and enumerable
  • Each rule is tested and narrowly scoped
  • No open-ended pattern matching

Deterministic Parse and Execution

Same program in language X always produces same output as same program in language Y.

What’s Out of Scope

Open-Ended Intent Extraction

Not supported:

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# This is NOT a valid multilingual program
print the sum of all numbers from one to ten

multilingual is not a natural language programming system. Programs must use explicit keywords.

Free-Form Conversational Programming

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# NOT supported
Add a function that greets users

Full Morphology and Synonym Resolution

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# In French, all of these would mean the same thing in natural French,
# but only the canonical keyword is accepted:
afficher(x)     # canonical alias — ACCEPTED
montrer(x)      # synonym — NOT accepted as a builtin alias
montrez(x)      # conjugated form — NOT accepted

Only the registered keyword form is recognized. This prevents ambiguity.

Arbitrary Grammar Extensions

Surface normalization patterns must be:

  1. Narrowly scoped (minimal pattern footprint)
  2. Test-backed (executor tests for each form)
  3. Non-overlapping (no ambiguity between rules)
  4. Based on actual linguistic usage (native speaker input preferred)

Ambiguity Policy

Prefer explicit token-level concepts over heuristic interpretation.

  1. Conflicting keyword mappings are disallowed by validation/tests
  2. Surface patterns are added incrementally with dedicated tests
  3. When in doubt, reject the form rather than guess intent

Example of an ambiguous form (rejected):

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# In Spanish, "para" could be:
# - LOOP_FOR ("for" loop)
# - PREP ("for" preposition, e.g., "para ti" = "for you")

In multilingual Spanish, para is defined as LOOP_FOR. If used in a non-loop context where it appears as an argument, the lexer still tokenizes it as LOOP_FOR. This is intentional — the controlled subset avoids contexts where para would be ambiguous.

Practical Authoring Rule

When onboarding a language:

Accept only forms that can be specified and tested as stable grammar rules.

Reject forms that require:

  • Broad NLP inference
  • Context-sensitive disambiguation
  • Morphological analysis
  • Semantic role labeling

Test before you accept. If a surface form requires a special-case rule to parse, add a specific test for it. If the rule is too broad or overlapping, narrow it.

The CNL approach is related to:

  • Controlled Natural Language (CNL) research — constrained subsets of natural languages with formal semantics
  • Racket #lang — explicit language selection at module boundary, shared semantic core
  • ALGOL 68 — multiple publication languages mapping to one formal definition

See Related Work for more context.

Evolution

The CNL scope boundary may evolve:

  • More surface patterns — expanding the set of accepted natural forms for existing languages
  • More aliases — additional localized built-in aliases beyond the current 41
  • New language packs — subject to same CNL rules

What will not change:

  • The requirement for deterministic parsing
  • The prohibition on open-ended NLP
  • The single-keyword-per-concept-per-language rule