<eTree>

<eTree> (embedding tree) provides an alternative to tree element for representing ordered rooted tree structures. 19.3 Another Tree Notation
Module nets — 19 Graphs, Networks, and Trees
In addition to global attributes att.typed (@type, @subtype)
value provides the value of an embedding tree, which is a feature structure or other analytic element.
Status Recommended when applicable
Datatype 

<rng:ref name="data.pointer"/>
data.pointer
Values A valid identifier of a feature structure or other analytic element.
Used by
eTree forest triangle model.divPart
May contain
core: label ptr ref
nets: eLeaf eTree triangle
Declaration 

<rng:element name="eTree">
 <rng:ref name="att.global.attributes"/>
 <rng:ref name="att.typed.attributes"/>
 <rng:optional>
  <rng:attribute name="value">
   <rng:ref name="data.pointer"/>
  </rng:attribute>
 </rng:optional>
 <rng:group>
  <rng:optional>
   <rng:ref name="label"/>
  </rng:optional>
  <rng:zeroOrMore>
   <rng:choice>
    <rng:ref name="eTree"/>
    <rng:ref name="triangle"/>
    <rng:ref name="eLeaf"/>
    <rng:ref name="model.ptrLike"/>
   </rng:choice>
  </rng:zeroOrMore>
 </rng:group>
</rng:element>
element eTree
{
   att.global.attributes,
   att.typed.attributes,
   attribute value { data.pointer }?,
   ( label?, ( eTree | triangle | eLeaf | model.ptrLike )* )
}
Example
<eTree n="ex1">
 <label>PP</label>
 <eTree>
  <label>P</label>
  <eLeaf>
   <label>with</label>
  </eLeaf>
 </eTree>
 <eTree>
  <label>NP</label>
  <eTree>
   <label>Art</label>
   <eLeaf>
    <label>the</label>
   </eLeaf>
  </eTree>
  <eTree>
   <label>N</label>
   <eLeaf>
    <label>periscope</label>
   </eLeaf>
  </eTree>
 </eTree>
</eTree>
Note
an optional label followed by zero or more embedding trees, triangles, or embedding leafs.