<if>

<if> defines a conditional default value for a feature; the condition is specified as a feature structure, and is met if it subsumes the feature structure in the text for which a default value is sought. 18.11 Feature System Declaration
組件iso-fs — 18 Feature Structures
屬性
屬於vDefault
可包含
iso-fs: binary default f fs numeric string symbol then vAlt vColl vLabel vMerge vNot
宣告
element if
{
   att.global.attributes,
   ( ( fs | f ), then, ( model.featureVal ) )
}
註
May contain a feature structure, followed by a feature value; the two are separated by a <then> element.