With each occurence of Record_key_1 identifying a new object, all subsequent records referring to that object until a new object is defined.

Sample input:
Record_key_1 | A | B | C |
Record_key_2 | 0 | 1 |
Record_key_2 | 2 | 3 |
Record_key_2 | 4| 5 |
Record_key_3 | a | b | c | d |
Record_key_3 | e | f | g | h |
Record_key_1 | D | E | F |
Record_key_2 | 6 | 7 |
Record_key_2 | 8 | 9 |
Record_key_3 | i | j | k | l |

= 2 objects total

Sample output:
<Object>
   <Object Properties>
      <Properties_1>A</Properties_1>
      <Properties_2>B</Properties_2>
      <Properties_3>C</Properties_3>
   </Object Properties>
   <Sub-object>
      <Sub-object characteristics_1>0</Sub-object characteristics_1>
      <Sub-object characteristics_2>1</Sub-object characteristics_2>
   </Sub-object>
   <Sub-object>
      <Sub-object characteristics_1>2</Sub-object characteristics_1>
      <Sub-object characteristics_2>3</Sub-object characteristics_2>
   </Sub-object>
   <Sub-object>
      <Sub-object characteristics_1>4</Sub-object characteristics_1>
      <Sub-object characteristics_2>5</Sub-object characteristics_2>
   </Sub-object>
   <Object user>
      <User details_1>a</User details_1>
      <User details_2>b</User details_2>
      <User details_3>c</User details_3>
      <User details_4>d</User details_4>
   </Object user>
   <Object user>
      <User details_1>e</User details_1>
      <User details_2>f</User details_2>
      <User details_3>g</User details_3>
      <User details_4>h</User details_4>
   </Object user>
</Object>

<Object>
   <Object Properties>
      <Properties_1>D</Properties_1>
      <Properties_2>E</Properties_2>
      <Properties_3>F</Properties_3>
   </Object Properties>
   <Sub-object>
      <Sub-object characteristics_1>6</Sub-object characteristics_1>
      <Sub-object characteristics_2>7</Sub-object characteristics_2>
   </Sub-object>
   <Sub-object>
      <Sub-object characteristics_1>8</Sub-object characteristics_1>
      <Sub-object characteristics_2>9</Sub-object characteristics_2>
   </Sub-object>
   <Object user>
      <User details_1>i</User details_1>
      <User details_2>j</User details_2>
      <User details_3>k</User details_3>
      <User details_4>l</User details_4>
   </Object user>
</Object>