Embedded fonts + generic font families

Good morning/evening,

Say the following is present in a TTML2 document:

  <resources>
    <font family="default" range="u+20-7f,u+90-9f">
      <source src="http://example.com/fonts/default.otf" type="font/otf"/>
    </font>
  </resources>

In the following snippet, is a presentation processor expected to use the
embedded font, or is the font selection sill left to the implementation?

<p tts:fontFamily="default">font above or application-selected?</p>

Best,

-- Pierre