This chapter focuses on XML-based document markup languages in two dominant groups of office suites: Microsoft Office 2007 and OpenOffice.org. There are plenty of other markup languages, which are covered well on Wikipedia:
http://en.wikipedia.org/wiki/Document_markup_language
http://en.wikipedia.org/wiki/List_of_document_markup_languages
http://en.wikipedia.org/wiki/Comparison_of_document_markup_languages