Underspecification

不完全赋值，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）音系学最近一些特征理论用来指主张底层音系表征式应尽量省略信息的各种理论，即主张表征式的内容应作最低程度的指定，也就是“不完全赋值”。这种主张背离早期生成音系学“完全”赋值的概念：音系部分的输出必须包含完全赋值的二分特征矩阵。不完全赋值理论关心的是，在多大程度上音系表征式内出现的特征区别不应以[+特征]和[-特征]的二分选择出现，而应在[+特征]和不加任何标记之间选择。这种理论因此特别考察哪些征值是可预测的，因而可以在表征式中不加指定而不致影响表层形式。

这种理论主要与词汇音系学有关，但存在好几种不完全赋值的模型，区别在于对最简性的理解。在有限的或对立不完全赋值模型中，只有羡余特征在词汇上不加指定（例如英语的阻塞音赋有带声特征值，因为是对立性的，而响音不需指定此值，因为是羡余的）。这种模型对词项形式中不完全赋值的程度加以限制，即只省略那些根据普世的同现条件可以预测的特征值，而其他特征都不可以不完全赋值。这种模型对立于绝对不完全赋值模型，后者允许表征式在任何场合都只指定一个值。此外，只有当规则会给一个特征指派错误的值时赋值才是必须的。这种模型不仅在底层表征式中省去可根据同现条件预测的特征值，而且还省去那些可从上下文自由的标记性陈述中预测的特征值。默认规则指派无标记值。不完全赋值理论还可采取其他立场，例如在任何情形下都不引入无标记值，因而所有特征都是有效的单值（缺值）特征。

（2）这一术语还用来指针对其他语言平面的某些模型，它们不要求对一种分析可能涉及的全部因素都加以指定。例如，语义学有一些形式化模型不对逻辑结构的所有特征都赋值（例如在表示辖域歧义时）。