---I think this particular nail (specifying that certain presentations must be distinct) doesn't require that hammer. There are two parts to the problem - one is representing that the distinction needs to be made, the other is representing whether the distinction is mandatory (can't display if not satisfied) or not. The latter is the problem you cite, the former is the one Evan raises. They're both required, but Evan's does require some kind of notational support in the stylesheet.
A couple more ways to represent this might include:
EM.class1 : font-weight != EM.class2 : font-weight
or
EM.class1, EM.class2 : font-weight = distinct
scott
-- scott preece motorola/mcg urbana design center 1101 e. university, urbana, il 61801 phone: 217-384-8589 fax: 217-384-8550 internet mail: [email protected]