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This direct link between gml:PointProperty and gml:Point is a deviation from the general AIXM principle of having xlink:href associations towards the feature level only. However, this direct association with the gml:Point property of the aixm:Navaid is the only solution identified for really encoding geometry dependencies at the GML level. In a source database, the association can still be towards the Navaid itself (as detailed in the next section). Only for data export/import purpose the reference would be towards the gml:Point directly.
Summary
In conclusion, there are two options for encoding point references in AIXM/GML:
- as a simple annotation
- as a local concrete xlink:href reference using gml:id
The most appropriate one depends on the intended usage of the data. Therefore, AIXM applications should offer the client the possibility to specify how such references should be exported: to be preserved or be replaced with copies of gml:Point elements, eventually including the reference as an annotation.