<fDecl>

<fDecl> (feature declaration) declares a single feature, specifying its name, organization, range of allowed values, and optionally its default value. 18.11 Feature System Declaration
組件iso-fs — 18 Feature Structures
屬性
nameindicates the name of the feature being declared; matches the name attribute of <f> elements in the text.
狀態 必備的
資料類型 
data.name
值 any string of characters
optionalindicates whether or not the value of this feature may be present.
狀態 非必備的
資料類型 
xsd:boolean
註
If a feature is marked as optional, it is possible for it to be omitted from a feature structure. If an obligatory feature is omitted, then it is understood to have a default value, either explicitly declared, or, if no default is supplied, the special value any. If an optional feature is omitted, then it is understood to be missing and any possible value (including the default) is ignored.
屬於fsDecl
可包含
iso-fs: fDescr vDefault vRange
宣告
element fDecl
{
   att.global.attributes,
   attribute name { data.name },
   attribute optional { xsd:boolean }?,
   ( fDescr?, vRange, vDefault? )
}