As a semantic language, DocBook documents do not describe what their contents "look like", but rather the "meaning" of those contents. For example, rather than explaining how the abstract for an article might be visually formatted, DocBook simply says that a particular section "is" an abstract. It is up to an external processing tool or application to decide where on a page the abstract should go and what it should look like or whether or not it should be included in the final output at all.