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The Digital NOTAM encoding is based on the general temporality rules of AIXM 5.1, as detailed in the Temporality Concept document. Thus, most Digital NOTAM encodings will produce TEMPDELTA TimeSlices for the affected AIXM features. For example, a temporary navaid out of service event will be encoded as a new TimeSlice with interpretation=TEMPDELTA for the corresponding Navaid and including a property operationalStatus=UNSERVICEABLE.
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Pure spatial filtering might still be applied as an initial pre-selection of the Events that need to be transmitted to a client. Therefore, the AIXM Event Schema needs to support the provision of a basic "bounding box" geometry, to be used in those scenarios that require basic spatial filtering. This is already supported in the model, because the Event is an AIXM feature and therefore has a bounding box as any other GML feature. Details about the calculation of the {{Bounding Box}} size are provided in a specific data encoding rule.
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