View source for ID-rule

An ID-rule ''X'' <math>\rightarrow</math> <math>Y_1,</math> <math>Y_2,</math> ..., <math>Y_n </math> is interpreted as a well-formedness condition for [[local tree|local trees]]: It licenses all local trees with a root ''X'' and daughters <math>Y_1,</math> <math>Y_2,</math> ..., <math>Y_n </math>. The order of the daughters dominated by ''X'' is considered to be irrelevant.

===See also===
* [[Generalized Phrase Structure Grammar]]
* [[ID/LP rules]]
* [[LP-rule]]

===Comment===
ID-rules were first introduced in [[Generalized Phrase Structure Grammar]]. Moder unification-based grammar formalisms like [[Head-Driven Phrase Structure Grammar]] use a small number of highly general ID schemata instead.

Formally, the righthand side of an ID-rule can be considered as a [[multi-set|multi sets]].

===Other Languages===
* German [[ID-Regel]]
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[[Category: Grammatical theory]]