offtopic: question for users who use oxygen and docbook - and customized profiling attribute

Hello.
 We're using oxygen, and was hoping to use a customized attribute for
profiling (instead of arch, condition, conformance, etc) we would like
"product"

Has anyone out there done this with oxygen?  what are the steps needed to
make custom attributes work in oxygen? oxygen is yelling at us because it
isn't declared in the dtd/schema.

LN