In spite of the large number of markup languages for the Web and for the Semantic Web, there is still little knowledge on how to define the markup of such languages. The REWERSE working group I1 on "Rule Modeling and Markup", which has been chartered for the time period 2004 to 2008, aims at gathering such knowledge for Web reasoning languages on the basis of a rule modeling language that provides a metamodel, or abstract syntax, for rules.