The <fo:root> object is the root (top) node for XSL-FO documents.
The children of the <fo:root> object are a single <fo:layout-master-set> object (which holds all masters used in the document), an optional <fo:declarations> object, and one or more <fo:page-sequence> objects.
Note: An XSL-FO document can contain multiple <fo:page-sequences> (e.g. each chapter of a document could be a separate <fo:page-sequence> - this would allow chapter-specific content, such as the chapter title, to be placed within the header or footer).
XSL-FO documents have a structure like this: