mesh without primitives clarification

Both 1.4 and 1.5 spec says:

... the element may contain zero or more of the primitive elements <lines>, <linestrips>, <polygons>, <polylist>, <triangles>, <trifans>, and <tristrips>.

it says that "may contain zero" which means that mesh may not contain any primitives.

if mesh has vertices and doesnt have any primitives, how can I render it then?

For instance:

<mesh>
  <source id="box-Pos"/> 
  <vertices id="box-Vtx">
    <input semantic="POSITION" source="#box-Pos">
  </vertices>
</mesh>

Can I assume that if there is no primitives in mesh then it must be render as <triangles> like below?

<mesh>
  <source id="box-Pos"/>
  <vertices id="box-Vtx">
    <input semantic="POSITION" source="#box-Pos">
  </vertices>

  <!-- Can I assume that this primitive is default? -->
  <triangles>
    <input semantic="VERTEX" offset="0" />
  </triangles>
</mesh>

KhronosGroup / OpenCOLLADA

mesh without primitives clarification #568