![]() ![]() According to the XML schema specification, an xsi:nil='true' attribute can be used in order to explicitly indicate that the element is empty. Therefore, it is the responsibility of the data providers to make sure that UUID values are correctly generated and are not altered by manual intervention.Įither abstract references (by gml:identifier) or internal references (by gml:id), as defined in the document, shall be used whenever the target record is contained in the same data set.ĪIXM uses extensively empty elements with an xlink:href attribute in order to code associations between features. It is not technically possible to verify that a UUID was actually generated with a correct UUID version 4 algorithm. However, resolving such conflicts might take a significant amount of energy and time. ![]() For example, a check that the xlink:href element of a Runway.associatedAirportHeliport property actually resolves into one and only one AirportHeliport and not into something else). In order to prevent problems that could occur from the use of pseudo-UUID, the validation rules for the AIS Data set include checks for the plausibility of the associations. Such errors are easier to detect when the two instances are of different kind (for example, a Runway and a Navaid), but more difficult when the two instances happen to be of the same kind (such as two Airspace). The consequence of using pseudo-UUID values could be for a data user to be confronted with two different feature instances that have the same gml:identifier value, while they are in reality different aeronautical information features. It is important to use a true UUID version 4 generator! Do not create and do not use pseudo-UUID values (a string of characters that looks like a UUID and which might even comply with the UUID version 4 syntax, but that was not generated with a proper UUID version 4 generator)!
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