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      Underspecification
      發布時間:2019年03月01日     發布人:nanyuzi  
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      Underspecification

      不完全賦值,不完全指定

       

      (1) In feature theories of phonology, a term characterizing various approaches which see it as desirable that information should be omitted from underlying phonological representations. The representations should be minimally specified, or underspecified. There is a departure from the concept of ‘full’ specification present in early generative phonology: the view that the output of the phonological component must contain fully specified binary feature matrices. Underspecification theory is concerned with the extent to which feature distinctions should appear in a phonological representation, not as a binary choice of [+feature] v. [-feature], but as a choice between [+feature] and no marking at all. It therefore looks in particular at which feature values are predictable and may thus be left unspecified in a representation without harming the surface form.

      The approach is chiefly associated with lexical phonology, but there are several underspecification models, which vary over their conceptions of minimality. In restricted or contrastive underspecification, only redundant features are lexically unspecified (e.g. in English, voicing would be specified for obstruents, where it is contrastive, but not for sonorants, where it is redundant). The approach limits the degree of underspecification in lexical forms by omitting only those feature values which are predictable on the basis of universal co-occurrence conditions. No other features may be underspecified. This contrasts with radical underspecification, which allows only one value to be specified in any given context in a representation. Moreover, such specifications are needed only when a rule would otherwise assign the wrong value to a feature. This approach omits from underlying representations not only the feature values which are predictable from co-occurrence conditions but also those which are predictable from context-free markedness statement. Default rules assign unmarked values. Other positions in underspecification theory are also possible, e.g. that the unmarked value is never introduced, so that all features are effectively single-valued (privative).

      (2) The term is also used in relation to other levels of language for any model which does not require the specification of all the factors potentially involved in an analysis. In semantics, for example, there are approaches to formalization which do not completely specify all features of logical structure (e.g. in representing scope ambiguities).

       

      (1)音系學最近一些特征理論用來指主張底層音系表征式應盡量省略信息的各種理論,即主張表征式的內容應作最低程度的指定,也就是“不完全賦值”。這種主張背離早期生成音系學“完全”賦值的概念:音系部分的輸出必須包含完全賦值的二分特征矩陣。不完全賦值理論關心的是,在多大程度上音系表征式內出現的特征區別不應以[+特征]和[-特征]的二分選擇出現,而應在[+特征]和不加任何標記之間選擇。這種理論因此特別考察哪些征值是可預測的,因而可以在表征式中不加指定而不致影響表層形式。

      這種理論主要與詞匯音系學有關,但存在好幾種不完全賦值的模型,區別在于對最簡性的理解。在有限的或對立不完全賦值模型中,只有羨余特征在詞匯上不加指定(例如英語的阻塞音賦有帶聲特征值,因為是對立性的,而響音不需指定此值,因為是羨余的)。這種模型對詞項形式中不完全賦值的程度加以限制,即只省略那些根據普世的同現條件可以預測的特征值,而其他特征都不可以不完全賦值。這種模型對立于絕對不完全賦值模型,后者允許表征式在任何場合都只指定一個值。此外,只有當規則會給一個特征指派錯誤的值時賦值才是必須的。這種模型不僅在底層表征式中省去可根據同現條件預測的特征值,而且還省去那些可從上下文自由的標記性陳述中預測的特征值。默認規則指派無標記值。不完全賦值理論還可采取其他立場,例如在任何情形下都不引入無標記值,因而所有特征都是有效的單值(缺值)特征。

      (2)這一術語還用來指針對其他語言平面的某些模型,它們不要求對一種分析可能涉及的全部因素都加以指定。例如,語義學有一些形式化模型不對邏輯結構的所有特征都賦值(例如在表示轄域歧義時)。

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      在线精品国产一区二区三区,欧美最猛性XXXXX大叫,亚欧美日韩香蕉在线播放视频