[Lot 4] AIXM-508 Allow multiple approach procedures to use the same TAA

Description

The multiplicity of the association between TerminalArrivalArea and InstrumentApproachProcedure is increased from one to many and “RNAV” is removed from the role name.

Rationale for change

See https://aixmccb.atlassian.net/browse/AIXM-255

The TerminalArrivalArea supports the encoding of Terminal Arrival Altitude (TAA), which are used for T or Y-bar PBN procedures. The standard TAA has three reference areas, based on the direction of the approach. In the current model, each TAA is related to a single InstrumentApproachProcedure, as indicated in the following diagram.

There exist many examples of TAA that are re-used for multiple procedures. For example, There are 29 GLS procedures currently published in Norway which all share TAAs with the RNP APCH procedure published to the same runway end. Therefore, it is proposed to increase the multiplicity of the InstrumentApproachProcedure in this association to allow 0…* instead of 0...1.

A smaller issue concerns the “approachRNAV” role name of the InstrumentApproachProcedure in relation with the TAA. ICAO PANS-OPS vol. 1 indicates that TAA is used in relation with PBN approaches. It is proposed to change the role name into “approach”, without specifying PBN or RNAV.

Impact assessment

[FWD_MAP_1:1] Data mapping is possible and no data loss occurs when data is exchanged from a system (A) that uses AIXM 5.1.1 for output towards a system (B) that uses AIXM 5.2 for input.

[BWD_MAP_LOSS] Data mapping is possible, but some data would be lost (or converted into Notes) when data is exchanged from a system (B) that uses AIXM 5.2 for output towards a system (A) that uses AIXM 5.1.1 for input.

Change Proposal details

In the UML model:

• For the association TerminalArrivalArea isFeederFor InstrumentApproachProcedure, on the InstrumentApproachProcedure side:
  • increase the multiplicity to 0…*
  • change the role name into approach (instead of approachRNAV)

The resulting model is shown in the following UML class diagram:

Mapping AIXM 5.1.1 to AIXM 5.2 (forward)

[MAPC-00]  For each TerminalArrivalArea that has an approachRNAV element, rename the element into approach.

Mapping AIXM 5.2 to AIXM 5.1.1 (backward)

[MAPC-05] The following algorithm shall be applied.

For each TerminalArrivalArea that has more than one approach element.

From the four backward mapping options discussed for this case, the first one (discard the additional occurrences) is not really possible due to the importance of the data that is mapped. The use of an extension is straightforward and does not need any further details.

The 3^rd option (create copies of the ‘source’ for each additional ‘destination’) and the 4^th option (backward mapping of the additional occurrences into a Note) are detailed in order to provide complete descriptions of these cases and conversion options.

3^rd option

The following mapping algorithm by multiplying the source class is proposed:

• Identify the occurrence of the approach occurrence of that is preserved
• For each additional occurrence of the approach element:
  • Remove the approach element
  • Create a copy of the TerminalArrivalArea class, with exactly the same child elements, except for:
    • gml:identifier, which gets as value a concatenation of the gml:identifier of the source (TerminalArrivalArea), followed by a separator (“-”) and the gml:identifier of the destination (InstrumentApproachProcedure) that is mapped;
    • approachRNAV, which gets only one occurence (that one that is being mapped);
    • Note that the gml:id might also need to be replaced, if the result of the conversion algorithm is an AIXM 5.1(.1) file, to avoid a conflict of XML ID values.

4^th option

 The following mapping into Note algorithm is proposed:

• Identify the occurrence of the approach occurrence of that is preserved and remove the other approach elements;
• rename the approach element that is preserved into approachRNAV
• Add an annotation.Note associated with the owner class having
• purpose=“OTHER:BACKWARD_MAPPING”;
• LinguisticNote.note=”approachRNAV[1].InstrumentApproachProcedure: <approach.xlink:href>;approachRNAV[2].InstrumentApproachProcedure: <approach.xlink:href>; etc.”
  • “[1]”, “[2]” indicate that this needs to be repeated as many times as necessary to cover all occurrences that are not preserved;
• propertyName=”approachRNAV”.

Mapping example

(Note: for mapping test data see: https://github.com/aixm/mapping_52_511/tree/master/AIXM-xxx) 

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