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Linglib.Theories.Phonology.Prosodic.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 (SonorityRank). 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 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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    @[implicit_reducible]
    instance Phonology.Syllable.instDecidableEqNatClass :
    DecidableEq NatClass
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    @[implicit_reducible]
    instance Phonology.Syllable.instReprNatClass :
    Repr NatClass
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    def Phonology.Syllable.instReprNatClass.repr :
    NatClass → ℕ → Std.Format
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      def Phonology.Syllable.NatClass.parkerSonority :
      NatClass → ℕ

      Parker (2002) 8-level sonority ranking.

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

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

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          def Phonology.Syllable.parkerSonorityOf (s : Segment) :
          ℕ

          Parker sonority of a segment (convenience).

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            def Phonology.Syllable.NatClass.toSonorityRank :
            NatClass → SonorityRank

            Map NatClass to the abstract SonorityRank. This collapses the Parker voicing distinction within obstruents (vls/vds → stop, vlf/vdf → fricative), connecting the fine-grained 8-level scale to the substance-free 6-level hierarchy that the grammar operates on.

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              theorem 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.