The FrameMaker document model for an unstructured document is essentially flat. You have to write “rules” (Mif2Go macros) to add the tag information that establishes a hierarchy.
§14.1.1 Accommodating HTML features in XML output
§14.1.2 Introducing structure with Mif2Go
§14.1.3 Introducing structure with XSLT
§14.1.4 Creating structure in FrameMaker
§14.1.5 Producing SGML with Mif2Go and XSLT