networkml 

The root element. 
Note: this element will only be present in a standalone NetworkML file (i.e. no cells or channels defined in the file).
For files covering many levels, neuroml will be the root element

Element Information

Model

populations , projections{0,1} , inputs{0,1}
Children: inputs, populations, projections

Attributes

QName Type Fixed Default Use Inheritable Annotation
lengthUnits LengthUnits optional 
Unit of all length measurements. Usually has the value <b>micrometer</b>. Note: length_units will be the preferred form in v2.0
length_units LengthUnits optional 
Unit of all length measurements. Usually has the value <b>micrometer</b>. Note: length_units will be the preferred form in v2.0
name xs:string optional
volumeUnits VolumeUnits cubic_millimeter optional 
Unit of all volume measurements.

Source 

<xs:element name="networkml" type="NetworkML">
  <xs:annotation>
    <xs:documentation>The root element. Note: this element will only be present in a standalone NetworkML file (i.e. no cells or channels defined in the file). For files covering many levels, neuroml will be the root element</xs:documentation>
  </xs:annotation>
</xs:element>

Sample