<root>

<root> (root node) represents the root node of a tree. 19.2 Trees
組件nets — 19 Graphs, Networks, and Trees
屬性
valueprovides the value of the root, which is a feature structure or other analytic element.
狀態 可應用時必備的
資料類型 
data.pointer
值 A valid identifier of a feature structure or other analytic element.
childrenprovides a list of identifiers of the elements which are the children of the root node.
狀態 必備的
資料類型 1–∞ occurrences of 
data.pointer
以空白鍵隔開
值 A list of valid identifiers.
註
If the root has no children (i.e., the tree is ‘trivial’), then the children attribute must be omitted. For technical reasons, it cannot be specified as root children=''.
ord (ordered) indicates whether or not the root is ordered.
狀態 可應用時必備的
資料類型 
data.xTruthValue
註
The value true indicates that the children of the root are ordered, whereas false indicates the are unordered.
Use if and only if ord is specified as partial on the <tree> element and the root has more than one child.
outDegreegives the out degree of the root, the number of its children.
狀態 非必備的
資料類型 
data.count
值 A nonnegative integer.
註
The in degree of the root is always 0.
屬於tree
可包含
core: label
宣告
element root
{
   att.global.attributes,
   attribute value { data.pointer }?,
   attribute children { list { data.pointer+ } },
   attribute ord { data.xTruthValue }?,
   attribute outDegree { data.count }?,
   label?
}
例子
<root xml:id="vp1" children="#vb1 #pn1" outDegree="2">
 <label>VP</label>
</root>
<leaf xml:id="vb1"/>
<leaf xml:id="pn1"/>