Decision Trees .xml file structure explanation

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Could you please help me understand the meaning of the .xml file structure that contain saved CvDTree model?

Here is the full .xml file.

Below is the part of it which, I suppose, contain the root node and next two nodes:

(...)
<nodes>
  <_>
    <depth>0</depth>
    <sample_count>1300</sample_count>
    <value>0.</value>
    <norm_class_idx>0</norm_class_idx>
    <Tn>9</Tn>
    <complexity>2</complexity>
    <alpha>93.</alpha>
    <node_risk>1200.</node_risk>
    <tree_risk>981.</tree_risk>
    <tree_error>119.</tree_error>
    <splits>
      <_><var>0</var>
        <quality>200.</quality>
        <le>2.6518464088439941e-001</le></_></splits></_>
  <_>
    <depth>1</depth>
    <sample_count>100</sample_count>
    <value>0.</value>
    <norm_class_idx>0</norm_class_idx>
    <Tn>2147483647</Tn>
    <complexity>1</complexity>
    <alpha>0.</alpha>
    <node_risk>0.</node_risk>
    <tree_risk>0.</tree_risk>
    <tree_error>0.</tree_error></_>
  <_>
    <depth>1</depth>
    <sample_count>1200</sample_count>
    <value>1.</value>
    <norm_class_idx>1</norm_class_idx>
    <Tn>2147483647</Tn>
    <complexity>1</complexity>
    <alpha>91.</alpha>
    <node_risk>1100.</node_risk>
    <tree_risk>981.</tree_risk>
    <tree_error>119.</tree_error>
    <splits>
      <_><var>0</var>
        <quality>200.</quality>
        <le>7.4546551704406738e-001</le></_></splits></_>
(...)