Labelling flow object sequence
The flow objects in a flow object sequence can be labelled
with a name.
Suppose you have a footnote paragraph inside a paragraph inside a
column-set-sequence. The footnote paragraph has to attached to the
foonote port of the column-set-sequence. This is achieved by
labelling the footnote paragraph.
When a labelled flow object is specified as part of the content of
some flow object, the label indicates whether the flow object belongs
to one of the sets of children of that flow object, and, if so, to
which stream (port) it belongs.
When a flow object is constructed and a flow object sequence is
specified for the content which includes labelled flow objects that
are not in one of the sets of children of the content, a flow object
sequence is returned containing the constructed flow object followed
by these labelled flow objects.
An unlabelled flow object belongs to the principal stream of
the flow object.