SVG <use> element with <set>

[ChRiedl]

It is a quite good idea to combine the SVG <use> construct with the possibility to modify the object with the <set> element. Is this a FITBIT invention ? I tried to find it in the W3C standard but was not able to find it, 

<svg>
  <use id="mybutton" href="#square-button-icon" y="5" fill="coral">
    <set href="#text"  attributeName="text-buffer" to="Steps" />
    <set href="#image" attributeName="href" to="steps.png" />
  </use>
</svg>

[ChRiedl · Accepted solution]

Forget my question !

I found it now : it is part of SMIL-Animation specification.