Although electronic publication has become common, almost all of it adheres to forms optimized for print. In an electronic environment, electronic documents interact with each other and this document-to-document interaction stands at the core of true electronic publication. Although technologies such as XML and the Semantic Web provide methodologies by which documents can more effectively interact, we are only now beginning to explore what new forms and functionality electronic publications will assume. This chapter takes its examples from the primary sources for cultural heritage, but the issues are general.