I would would like to suggest that the measure element be added
to the typed class so that it has both type and subtype attributes.
The additional subtype attirbute will be useful in dealing with
currency and probably other measurements as well.
<p>This book costs <measure type="currency" subtype="USD"
In the above example, the currency symbol "$" in the reg attribute
is not a precise indicator of the type of currency, since it is used
for both Candian and US dollars.
I think this is a general enough case that it might merit a change in