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Linglib.Theories.Phonology.Syllable.NaturalClass

Natural Classes and the Parker Sonority Scale #

@cite{parker-2002}

The 8-level Parker sonority scale refines @cite{clements-1990}'s 6-level hierarchy by splitting obstruents into four classes based on [±continuant] and [±voice]:

ClasssoncontvoiceRank
Voiceless stops−−−1
Voiced stops−−+2
Voiceless fric.−+−3
Voiced fricatives−++4
Nasals+−±5
Liquids / Taps++±6
Glides++±7
Vowels++±8

Sonorants (ranks 5–8) are distinguished by [±approximant], [±consonantal], and [±syllabic], exactly as in the Clements scale (sonorityOf). The Parker refinement adds [±voice] only within obstruents.

This finer granularity is needed for sonority-conditioned gradient phenomena such as intrusive vowel insertion in Tarifit Berber (@cite{afkir-zellou-2025}).

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inductive Theories.Phonology.Syllable.NatClass :
Type

Natural-class partition for the 8-level Parker sonority scale. Refines the Clements 6-level hierarchy by splitting obstruents into four voicing × continuancy classes.

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    instance Theories.Phonology.Syllable.instDecidableEqNatClass :
    DecidableEq NatClass
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    def Theories.Phonology.Syllable.instBEqNatClass.beq :
    NatClass → NatClass → Bool
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      instance Theories.Phonology.Syllable.instBEqNatClass :
      BEq NatClass
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      instance Theories.Phonology.Syllable.instReprNatClass :
      Repr NatClass
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      def Theories.Phonology.Syllable.instReprNatClass.repr :
      NatClass → Nat → Std.Format
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      • One or more equations did not get rendered due to their size.
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        def Theories.Phonology.Syllable.NatClass.parkerSonority :
        NatClass → Nat

        Parker (2002) 8-level sonority ranking.

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          def Theories.Phonology.Syllable.natClassOf (s : Segment) :
          NatClass

          Classify a segment into the Parker 8-level scale. Follows the feature decomposition of sonorityOf but additionally splits obstruents by [±voice] (@cite{parker-2002}).

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          • One or more equations did not get rendered due to their size.
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            def Theories.Phonology.Syllable.parkerSonorityOf (s : Segment) :
            Nat

            Parker sonority of a segment (convenience).

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              def Theories.Phonology.Syllable.NatClass.clementsSonority :
              NatClass → Nat

              Map NatClass to the Clements 6-level rank.

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                theorem Theories.Phonology.Syllable.parker_refines_clements (nc : NatClass) :
                nc.clementsSonority = match nc with | NatClass.vls => 0 | NatClass.vds => 0 | NatClass.vlf => 1 | NatClass.vdf => 1 | NatClass.nasal => 2 | NatClass.liquid => 3 | NatClass.glide => 4 | NatClass.vowel => 5

                The Parker scale is a strict refinement of Clements: every rank maps to the correct Clements rank.

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                theorem Theories.Phonology.Syllable.parker_strictly_monotone (a b : NatClass) (h : a ≠ b) :
                a.parkerSonority < b.parkerSonority ∨ a.parkerSonority > b.parkerSonority

                Parker sonority is strictly monotone: the ranking is a total order.