Documentation

Linglib.Discourse.Accessibility

Accessibility — Ariel's referential-form scale #

AccessibilityLevel: the 18-tier Accessibility Marking Scale of [Ari90], reproduced in [Ari01]'s overview (least accessible fullNameMod to most accessible zero), with rank (and the LinearOrder it induces), the three form-function criteria (informativity, rigidity, attenuation), the coarsening toDefinitenessLevel to Prominence.DefinitenessLevel, and the form-correlate bridge GivennessStatus.toAccessibility.

Accessibility and definiteness are non-monotonically related (full names are less accessible than definite descriptions, yet first/last names are more accessible; names are also more prominent for DOM), so they are separate types and toDefinitenessLevel is many-to-one and non-monotone.

Sibling of Features/Givenness.lean (GHZ-6): this classifies forms, GivennessStatus classifies entities. Also here: NextMentionBias.

Accessibility marking scale #

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inductive Discourse.AccessibilityLevel :
Type

The Accessibility Marking Scale of [Ari90], as printed in [Ari01]: classes of referring expressions ordered from least to most accessible. Speakers use more reduced forms for more accessible referents.

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    @[instance_reducible]
    instance Discourse.instDecidableEqAccessibilityLevel :
    DecidableEq AccessibilityLevel
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    @[instance_reducible]
    instance Discourse.instReprAccessibilityLevel :
    Repr AccessibilityLevel
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    def Discourse.instReprAccessibilityLevel.repr :
    AccessibilityLevel → ℕ → Std.Format
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      @[instance_reducible]
      instance Discourse.instFintypeAccessibilityLevel :
      Fintype AccessibilityLevel
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      @[instance_reducible]
      instance Discourse.instInhabitedAccessibilityLevel :
      Inhabited AccessibilityLevel
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      def Discourse.AccessibilityLevel.rank :
      AccessibilityLevel → ℕ

      Numeric rank: 0 (lowest accessibility) to 17 (highest). Higher rank = higher accessibility = more reduced form.

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        @[instance_reducible]
        instance Discourse.instLinearOrderAccessibilityLevel :
        LinearOrder AccessibilityLevel

        fullNameMod < ⋯ < zero (ordered by accessibility rank).

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        Form-function criteria #

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        def Discourse.AccessibilityLevel.informativity :
        AccessibilityLevel → ℕ

        Informativity: approximate lexical content, encoded as an ordinal ranking (0–4). Anti-correlated with accessibility (more informative → lower rank). Values are illustrative, encoding the relative ordering described in [Ari01], not exact content-word counts.

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          def Discourse.AccessibilityLevel.rigidity :
          AccessibilityLevel → ℕ

          Rigidity: the ability to uniquely pick out a referent from form alone, independent of context. Anti-correlated with accessibility. Proper names are rigid designators; definite descriptions are descriptive but context-dependent; pronouns and zeros carry only person/number/gender features and are maximally non-rigid.

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            def Discourse.AccessibilityLevel.attenuation :
            AccessibilityLevel → ℕ

            Attenuation: degree of phonological reduction, positively correlated with accessibility (0 = full, 5 = zero). Cliticized pronouns are shortened free pronouns; verbal agreement inflections are bound morphemes, more reduced still; zero has no phonological material ([Ari01]).

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              Definiteness coarsening #

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              def Discourse.AccessibilityLevel.toDefinitenessLevel :
              AccessibilityLevel → Features.Prominence.DefinitenessLevel

              Coarsening: each accessibility level maps to one of the 5 DefinitenessLevel categories used for differential argument marking. This is a many-to-one, non-monotone mapping — names are less accessible than definite descriptions but more prominent for DOM.

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                Next-mention bias #

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                inductive Discourse.NextMentionBias :
                Type

                Next-mention bias: how likely a discourse referent is to be mentioned again in the subsequent utterance. Driven by thematic roles, coherence relations, and discourse structure.

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                  @[instance_reducible]
                  instance Discourse.instDecidableEqNextMentionBias :
                  DecidableEq NextMentionBias
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                  @[instance_reducible]
                  instance Discourse.instReprNextMentionBias :
                  Repr NextMentionBias
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                  def Discourse.instReprNextMentionBias.repr :
                  NextMentionBias → ℕ → Std.Format
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                    def Discourse.NextMentionBias.predictedForm :
                    NextMentionBias → AccessibilityLevel

                    Prototype form choice for a next-mention bias: high bias → unstressed pronoun; low bias → full name.

                    This encodes the expectancy hypothesis — next-mention predictability drives form reduction — which [RA17] defends and [KR13] rejects (production there tracks topichood, with next-mention probability affecting interpretation only).

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                      Givenness projection #

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                      def Features.GivennessStatus.toAccessibility :
                      GivennessStatus → Discourse.AccessibilityLevel

                      Prototypical accessibility level for each givenness status. The four definite rows are [GHZ93]'s own form correlates (unstressed pronoun, bare demonstrative, demonstrative NP, definite description); the two indefinite statuses (referential = "indefinite this N", typeIdentifiable = "a N") have no form on the accessibility scale, so their rows are editorial rank-alignment, not form identity. [Ari01] criticizes the givenness hierarchy (no evidence for scalar distinctions below its top statuses) rather than endorsing such a projection.

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