Which is the Real XMLSS?

I'm working with reading a spreadsheet file exported by a web application we're developing. The developer who worked on the export function informed me that the format is XMLSS.

This is an abridged sample of what our application exports:

<?xml version="1.0"?>
<ss:Workbook xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet">
  <ss:Styles>
    <ss:Style ss:ID="1">
      <ss:Font ss:Bold="1"/>
    </ss:Style>
  </ss:Styles>
  <ss:Worksheet ss:Name="Sheet1">
    <ss:Table>
      <ss:Row ss:StyleID="1">
        <ss:Cell>
          <ss:Data ss:Type="String">Challenge ID</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Challenge Name</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Challenge Date/Time (Local)</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">First Name</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Last Name</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">DOB</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Gender</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Email</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Mobile Number</ss:Data>
        </ss:Cell>
      </ss:Row>
      <ss:Row>
        <ss:Cell>
          <ss:Data ss:Type="String">509373</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Run the Furthest</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">January 04, 2015 8:11 AM</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">John</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Smith</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Dec 25, 1984</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">Male</ss:Data>
        </ss:Cell>
        <ss:Cell>
          <ss:Data ss:Type="String">JohnSmith@Challengine.com</ss:Data>
        </ss:Cell>
      </ss:Row>
    </ss:Table>
  </ss:Worksheet>
</ss:Workbook>

However, I looked up XMLSS and found this wikipedia page: http://ift.tt/1w6S8zy

With this example of XMLSS:

<?xml version="1.0"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
 xmlns:o="urn:schemas-microsoft-com:office:office"
 xmlns:x="urn:schemas-microsoft-com:office:excel"
 xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
 xmlns:html="http://ift.tt/qQdaDR">
 <Worksheet ss:Name="Sheet1">
  <Table ss:ExpandedColumnCount="2" ss:ExpandedRowCount="2" x:FullColumns="1" x:FullRows="1">
   <Row>
    <Cell><Data ss:Type="String">Name</Data></Cell>
    <Cell><Data ss:Type="String">Example</Data></Cell>
   </Row>
   <Row>
    <Cell><Data ss:Type="String">Value</Data></Cell>
    <Cell><Data ss:Type="Number">123</Data></Cell>
   </Row>
  </Table>
 </Worksheet>
</Workbook>

These two examples seem to be quite different in their format.

Question:

Which one of these is the real XMLSS?

Or are they both, and there are multiple specifications? If so, what are the names of these specifications?

Or if one of these isn't XMLSS, then what is it?