12.6.1 Sequence Flow Object Class
A sequence flow object class is formatted to produce the concatenation of the areas produced by each of its children.  It has a single principal port.  Its children may be inlined or displayed.

NOTE 55

A sequence flow object is useful for specifying inherited characteristics.  For example, a sequence flow object with a specification of a font-posture: characteristic may be constructed for an emphasized phrase element in a paragraph.
A port of a flow object shall accept a sequence flow object if and only if it would accept each of the flow objects in that sequence.