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Topological consistency

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This is a question of interpretation, concerning the IR requirement 'metadata required for interoperability' 'Topological Consistency' (see section 8.2 in DataSpecification_HY_v3.1).

"This element is mandatory only if the data set includes types from the Generic Network Model and does not assure centreline topology (connectivity of centrelines) for the network."

At 10.2.2 of the specification, it is clear that 'centreline' here 'a line that approximates the centre of the real world object' and 'the primary way to represent a network geometry'. WatercourseLink & HydroNode specialise (extend) Link & Node from the Generic Network Model.

Is it correct to assume that if a dataset populates WatercourseLink.startNode and .endNode, then it 'assures centreline topology', so need no provide a Topological Consistency element.

Or is the intention that this element is populated by calculating discrepancies in the geometric position of the vertices at the ends of the WatercourseLink.centrelineGeometry and HydroNode.geometry?

(Perhaps it could be avoided if the model included explicit topology as defined in ISO 19107; or is the link-node model considered explicit enough?)