Delta for multi-occurring property with schedule Temporary change of multi-occurring property that overlaps a permanent change
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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
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. 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
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If this situation is not allowed to happen then the AIXM-TM should explicitly state this.
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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
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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.
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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.
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Figure 36 – Solving the delta overlap issue for a multi-occurring property with schedule by encoding the temporary change via two Tempdeltas