The when condition language¶

A root phoneme or allophone may carry an optional when block describing the phonetic context in which it is eligible. The language is small and explicit: a few atomic predicates combined with implicit AND and a binary OR.

Shape¶

A when block must have explicit braces, at least one child expression, and zero arguments or properties. A root and an allophone each have at most one when, and the two are evaluated independently — there is no inheritance between them.

when {
    or {
        group {
            word-position "final"
            syllable-position "coda"
        }
        previous-phoneme "s"
    }
}

Atomic predicates¶

Each predicate takes exactly one string argument, with no block and no properties.

Combining predicates¶

• when { ... } and group { ... } implicitly AND their direct children.
• or { a b } takes exactly two direct expressions and means OR. Nested or is allowed, including cross-category alternatives.
• group requires ≥ 2 direct expressions.
• There is no explicit and or not node. Unknown nodes are rejected.
• Repeated predicates are allowed — even contradictory ones. The structure is preserved; nothing is simplified.

Limits¶

• At most 16 atomic predicates per when, across all branches.
• At most 8 nested group/or levels along any path (the root when and the leaves are not counted).
• The generic KDL parser independently caps nesting depth at 64.

Semantics¶

Word position¶

Word position is defined over the sequence of underlying root phonemes in a word:

• initial — the first root phoneme.
• final — the last root phoneme.
• medial — neither first nor last.

A single-root-phoneme word is both initial and final, never medial.

Syllable position¶

onset, nucleus, and coda refer to the generator-assigned syllable components, not something inferred from the consonant/vowel group. Every phoneme inside a multi-phoneme component matches that component's position.

Neighbors¶

previous-phoneme and next-phoneme refer to the immediately adjacent underlying root identity. They look across syllable boundaries but not across word boundaries:

• A missing neighbor (for example, no previous phoneme at the start of a word) makes the predicate false — this is not a validation error.
• A reference to an allophone resolves to its owning root.
• Forward and self references are allowed, resolved after the whole inventory is collected. There is no circularity, because references are to underlying roots, not surface pronunciations.

Eligibility, not probability¶

The evaluator is a pure function over a supplied context (word position, generator-assigned syllable roles, neighbors). It returns an eligibility set — never a probability, weight, or priority. If no pronunciation is eligible in a context, the set is empty and there is no fallback; the inventory is still valid.

Canonical ordering¶

Inside when, group, and or, the direct child expressions are sorted recursively using the Canonical Condition Sorting Key v1. Tree structure and duplicate predicates are preserved; there is no boolean simplification, flattening, or reference rewriting. See Canonical serialization.