Here is a listing for the <defs> section of an SVG file. This is where the definitions for gradients, patterns, markers, etc. are stored. Parts of the definitions have been omitted.

  <defs                                                          
     id="defs4">
    <marker                                                      
       inkscape:stockid="Arrow2Lend"
       orient="auto"
       refY="0.0"
       refX="0.0"
       id="Arrow2Lend"
       style="overflow:visible;">
       ...
    </marker>
    <linearGradient                                              
       inkscape:collect="always"
       id="linearGradient2311">
      <stop ...
    </linearGradient>
    <pattern                                                     
       patternUnits="userSpaceOnUse"
       width="320.99999"
       height="289.72575"
       patternTransform="translate(88.07143,25.99358)"
       id="pattern2319">
      <rect ....
    </pattern>
  </defs>