Poko Phonological Fragment — Tonal

@cite{mcpherson-dryer-2021} @cite{mcpherson-2022} @cite{mcpherson-lamont-2026}

Poko (also Poko-Rawo, ISO 639-3: not assigned, Glottocode: poko1259) is a Skou language spoken in Sandaun Province, Papua New Guinea, near the border with West Papua. ~100 speakers as of @cite{mcpherson-dryer-2021}.

Tone system

Three contrastive tone levels — high (H), mid (M), low (L) — plus toneless syllables and floating tones. Lexical melodies range from Ø (toneless) through M, MH, LM, LH, M^H (M with floating H); @cite{mcpherson-2022} argues the lexical inventory excludes simple L and H melodies as a response to OCP markedness pressures.

The TBU is the syllable; stems are mono- or disyllabic with vowel-final stems undergoing apocope phrase-medially (paper, ex. 1).

Floating tones

Floating L tones appear at the LEFT edge of stems; floating H tones at the RIGHT edge (paper, §2.2). Postlexically, floating L tones remain floating (causing downstep), while floating H tones either dock rightward, dock leftward (tautomorphic, blocked by *TAUTDOCK), or delete (paper, §3.2).

Stems represented here

Just enough syllables for the @cite{mcpherson-lamont-2026} fig. 3 demonstration: kāk (3sg.m possessive), rī (pig stem with /M^H/ melody), dō (get verb with /M^H/ melody). Promote to a fuller fragment when a second Poko paper arrives.

Morpheme IDs

Each Poko stem is one morpheme. We assign Nat morpheme IDs in left-to-right order of first appearance in the fig. 3 input: kāk = 0, rī = 1, dō = 2. The IDs are consumed by *TAUTDOCK and *CROWD via the SegSpec/ToneSpec morpheme fields.

inductive Fragments.Poko.Syll : Type

Poko syllables represented for the @cite{mcpherson-lamont-2026} tableaux: fig. 3 (kak, ri, do); eq. (24) (nan, ri, na); eq. (27) (kak, ka); eq. (30) (kak, ili). Promote to a fuller stem inventory when a second Poko paper arrives.

• kak : Syll
• ri : Syll
• do : Syll
• nan : Syll
• na : Syll
• ka : Syll
• ili : Syll
• ne : Syll

@[implicit_reducible]

instance Fragments.Poko.instDecidableEqSyll : DecidableEq Syll

Equations

• Fragments.Poko.instDecidableEqSyll x✝ y✝ = if h : x✝.ctorIdx = y✝.ctorIdx then isTrue ⋯ else isFalse ⋯

def Fragments.Poko.instReprSyll.repr : Syll → ℕ → Std.Format

Equations

• Fragments.Poko.instReprSyll.repr Fragments.Poko.Syll.kak prec✝ = Repr.addAppParen (Std.Format.nest (if prec✝ ≥ 1024 then 1 else 2) (Std.Format.text "Fragments.Poko.Syll.kak")).group prec✝
• Fragments.Poko.instReprSyll.repr Fragments.Poko.Syll.ri prec✝ = Repr.addAppParen (Std.Format.nest (if prec✝ ≥ 1024 then 1 else 2) (Std.Format.text "Fragments.Poko.Syll.ri")).group prec✝
• Fragments.Poko.instReprSyll.repr Fragments.Poko.Syll.do prec✝ = Repr.addAppParen (Std.Format.nest (if prec✝ ≥ 1024 then 1 else 2) (Std.Format.text "Fragments.Poko.Syll.do")).group prec✝
• Fragments.Poko.instReprSyll.repr Fragments.Poko.Syll.nan prec✝ = Repr.addAppParen (Std.Format.nest (if prec✝ ≥ 1024 then 1 else 2) (Std.Format.text "Fragments.Poko.Syll.nan")).group prec✝
• Fragments.Poko.instReprSyll.repr Fragments.Poko.Syll.na prec✝ = Repr.addAppParen (Std.Format.nest (if prec✝ ≥ 1024 then 1 else 2) (Std.Format.text "Fragments.Poko.Syll.na")).group prec✝
• Fragments.Poko.instReprSyll.repr Fragments.Poko.Syll.ka prec✝ = Repr.addAppParen (Std.Format.nest (if prec✝ ≥ 1024 then 1 else 2) (Std.Format.text "Fragments.Poko.Syll.ka")).group prec✝
• Fragments.Poko.instReprSyll.repr Fragments.Poko.Syll.ili prec✝ = Repr.addAppParen (Std.Format.nest (if prec✝ ≥ 1024 then 1 else 2) (Std.Format.text "Fragments.Poko.Syll.ili")).group prec✝
• Fragments.Poko.instReprSyll.repr Fragments.Poko.Syll.ne prec✝ = Repr.addAppParen (Std.Format.nest (if prec✝ ≥ 1024 then 1 else 2) (Std.Format.text "Fragments.Poko.Syll.ne")).group prec✝

@[implicit_reducible]

instance Fragments.Poko.instReprSyll : Repr Syll

Equations

• Fragments.Poko.instReprSyll = { reprPrec := Fragments.Poko.instReprSyll.repr }

@[implicit_reducible]

instance Fragments.Poko.instInhabitedSyll : Inhabited Syll

Equations

• Fragments.Poko.instInhabitedSyll = { default := Fragments.Poko.instInhabitedSyll.default }

def Fragments.Poko.instInhabitedSyll.default : Syll

Equations

• Fragments.Poko.instInhabitedSyll.default = Fragments.Poko.Syll.kak

def Fragments.Poko.Syll.morphemeId : Syll → Phonology.Autosegmental.MorphemeId

Stable morpheme ID per stem. IDs are assigned to keep inputs from distinct paper examples non-overlapping.

Equations

• Fragments.Poko.Syll.kak.morphemeId = 0
• Fragments.Poko.Syll.ri.morphemeId = 1
• Fragments.Poko.Syll.do.morphemeId = 2
• Fragments.Poko.Syll.nan.morphemeId = 3
• Fragments.Poko.Syll.na.morphemeId = 4
• Fragments.Poko.Syll.ka.morphemeId = 5
• Fragments.Poko.Syll.ili.morphemeId = 6
• Fragments.Poko.Syll.ne.morphemeId = 7

def Fragments.Poko.seg (s : Syll) : Phonology.Autosegmental.SegSpec Syll

Wrap a syllable as a SegSpec carrying its morpheme ID.

Equations

• Fragments.Poko.seg s = { seg := s, morpheme := s.morphemeId }

def Fragments.Poko.mTone (s : Syll) : Phonology.Autosegmental.ToneSpec

An M tone belonging to the morpheme of syllable s (the lexical M of an /M^H/ stem).

Equations

• Fragments.Poko.mTone s = { tone := Phonology.Autosegmental.RegisterTier.TRN.M, morpheme := s.morphemeId }

def Fragments.Poko.hTone (s : Syll) : Phonology.Autosegmental.ToneSpec

An H tone belonging to the morpheme of syllable s (the floating H of an /M^H/ stem).

Equations

• Fragments.Poko.hTone s = { tone := Phonology.Autosegmental.RegisterTier.TRN.H, morpheme := s.morphemeId }

def Fragments.Poko.lTone (s : Syll) : Phonology.Autosegmental.ToneSpec

An L tone belonging to the morpheme of syllable s (the L of an /LH/ lexical stem like ìlí).

Equations

• Fragments.Poko.lTone s = { tone := Phonology.Autosegmental.RegisterTier.TRN.L, morpheme := s.morphemeId }