[XeTeX] Small Caps in Latex

[Atip Asvanund]

On Thu, 1 Jul 2004, Bruno Voisin wrote:
> That's because Letter Case = Small Caps is not available for Warnock
> Pro. The file AAT-info.tex which is part of the XeTeX sample files will
> tell you what's exactly available for each font (please make sure you
> run XeTeX on it in plain TeX mode, not LaTeX).

I find that Small Caps are not available for several fonts. Is there a way
to simulate this (e.g., by using Caps of the same font at a smaller size)?
Or is there not an automatable workaround at all?

Thank you,

Atip