Question on Font Descriptors

How does one reference a font descriptor to use the selected font?

From the 'Robson Celtic' example in the spec, it seems you use the name
specified by the 'font-family' descriptor.  However, in the example under
15.3.9, all the font descriptors have the same font family name.  There
doesn't seem to be anything that allows you to call upon a particular font
mapped from a specific font-descriptor.
Andrew n marshall
  student - artist - programmer
    http://www.media-electronica.com/anm-bin/anm
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