Formatting Objects are truly wonderful

FoFo — Abstract base formatting object
basic-link
bidi-override
FoBlockBlock
block
block-container
FoBlockLayout
FoBlockWhitespace
FoCharacter
color-profile
conditional-page-master-reference
declarations
external-graphic
float
flow
footnote-body
footnote
initial-property-set
inline
inline-container
instream-foreign-object
layout-master-set
leader
list-block
list-item-body
list-item
list-item-label
marker
fo-marker-parent
multi-case
multi-properties
multi-property-set
multi-switch
multi-toggle
page-number
page-number-citation
page-sequence — 'page-sequence' formatting object
page-sequence-master
region-after — 'region-after' formatting object
region-before
region-body
region-end
region-start
repeatable-page-master-alternatives
repeatable-page-master-reference
fo-retrieve-marker
root — 'root' formatting object
simple-page-master
single-page-master-reference
static-content
table-and-caption
table-body
table
table-caption
table-cell — 'table-cell' formatting object
table-column
table-footer
table-header
FoTablePart
table-row
FoText
title
FoTree — Top of the FO tree
FoWrapperBlock
FoWrapper
FoWrapperInline
FoWrapperInlineEmpty
FoWrapperWhitespace