Delta for multi-occurring property with schedule Temporary change of multi-occurring property that overlaps a permanent change

Copyright © 2011 Open Geospatial Consortium, Inc. All Rights Reserved. 85 Figure 32 – Permanent change of a multi occurring feature property occurring during the valid time of a temporary change of that property Here, property P2 is multi occurring. Its static set of values {1,2,3} in Baseline 1 is changed permanently via Permdelta 2 to {1,4,5}. However, a temporary change is applied to the property via Tempdelta 1 – adding value ‘6’ and its valid time contains the valid time of the permanent change. This situation is not explicitly described in the AIXM Temporality Model. As it is not forbidden, it may occur 8 . In such a situation it does not matter whether the multi occurring property P2 does or does not have a schedule - either way it is unclear how the Tempdelta should incorporate the unchanged property values from the static information Baseline 1 and 2. Should all unchanged values be incorporated? As the set of values for P2 changes permanently via Permdelta 2, the values that would be incorporated from the Baselines 1 and 2 in Tempdelta 1 following the current rule from 8 If this situation is not allowed to happen then the AIXM-TM should explicitly state this. 86 Copyright © 2011 Open Geospatial Consortium, Inc. All Rights Reserved. the Temporality Model would not be valid throughout its validTime in Figure 32, only value’1’ would be valid throughout the validTime of Tempdelta 1 – although that should be the contract for a Tempdelta. Furthermore, the value of P2 in Tempdelta 1 does not even need to contain such values as long as the value of P2 is fully defined throughout the valid time of P2 see Temporality Model section 2.7 for further details. During OWS-8, different options for solving this issue were developed, depending on whether the multi-occurring property is or is not a PropertyWithSchedule again, see Temporality Model section 2.7 for further details. If P2 is a property without schedule, then a solution is to model the temporary change via two Tempdeltas as shown in the following figure. Figure 33 – Handling the delta overlap issue for a multi-occurring property without schedule Copyright © 2011 Open Geospatial Consortium, Inc. All Rights Reserved. 87 As we can see, the validTime of the Permdelta equals the end time of Tempdelta 1.1 and the start time of Tempdelta 1.2. By splitting the temporary change, the information can easily be merged with the baseline information that is still valid. If P2 is a property with schedule, then there are two options for solving the issue – see Figure 34. Figure 34 – Options for solving the delta overlap issue for a multi-occurring property with schedule In this example, the schedule of P2 in Baseline 1 defines that the set of valid values for P2 alternates between {1} and {2,3}. The permanent change introduced by Permdelta 2 changes the schedule so that the set of valid values for P2 alternate between {1} and {4,5}. The temporary change would now add the value ‘6’ to the set of valid values – for the purpose of this example let us assume that this value is not constant but valid at the same time that the value sets {2,3} and {4,5} are valid. This can be modeled and encoded in two ways. On the one hand, the schedule can be adapted to take the additional value into account see Figure 35. On the other hand, the temporary change can again be modeled via two distinct Tempdeltas see Figure 36. 88 Copyright © 2011 Open Geospatial Consortium, Inc. All Rights Reserved. Figure 35 – Solving the delta overlap issue for a multi-occurring property with schedule via the schedule itself By appropriately encoding the schedule via property values with according timesheets, the valid sets of values for P2 can correctly be represented throughout the validTime of a single Tempdelta. Copyright © 2011 Open Geospatial Consortium, Inc. All Rights Reserved. 89 Figure 36 – Solving the delta overlap issue for a multi-occurring property with schedule by encoding the temporary change via two Tempdeltas

10.1.4.3 Recommendation

Section 3.5 in the Temporality Model should be revised. On the one hand, it needs to take changes for multi-occurring properties with schedule into account. On the other hand, it needs to account for the edge case of a permanent change to a multi occurring property that occurs during a temporary change of that property. For the latter, a recommendation to handle the situation by encoding two distinct Tempdeltas should be added. This appears to be the easiest solution which works for multi-occurring properties with and without schedule. However, being able to model the temporary change as a single Tempdelta may be useful for multi-occurring properties with schedule. This should therefore not be prohibited by the Temporality Model. 90 Copyright © 2011 Open Geospatial Consortium, Inc. All Rights Reserved.

10.1.5 Incorporate Extension Property Handling

During the FAA SAA Dissemination Pilot see OGC 11-055 the handling of AIXM feature and object extension properties was discussed. More specifically, the correct handling according to the rules defined in the AIXM Temporality Model. The discussion quickly revealed that the Temporality Model itself does not clearly specify how extension properties are to be handled. This section summarizes the result of the discussion. The Temporality Model should be revised to incorporate the instructions for handling AIXM extension properties. The following diagram shows an extension of the AIXM 5.1 Airspace feature that was used to add Special Use Airspace SUA information to that feature type in the SAA Pilot. Figure 37 – Special Use Airspace Feature extension for AIXM 5.1 Another extension shown in the following figure adds Special Activity Airspace SAA information to an AIXM 5.1 Airspace feature.