The documentation for "input" in "edges_type" (B-REP) reads: Five input elements are needed to define an edge, one for referencing the curve, two for referencing the two vertices, one for the orientation of the first vertex (the second is the opposite of the first) and one for the parametric values of the curve. However, it seems to only need 4 inputs now, from specification: Four <input> elements are needed to define an edge: • One with semantic="CURVE" to reference the corresponding geometric element for the edge. • Two with semantic="VERTEX" to reference the two vertices that limit each edge. • One with semantic="PARAM" to set the parametric values (start and end parameters) of the curve.

Clarifying: the <xs:documentation> in the schema for edges_type says that it needs 5, but definition is minoccurs=4, as described (presumably correctly) in the specification. (Currently is assigned to mcbarnes.)