Case Study: Restricting Role on Emphasis

<!ENTITY % emphasis.role.attrib
        role    (normal|emphasis)       "normal"
>

<!ENTITY % docbook PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
          "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"
>

%docbook;