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Info
titleProposal
  1. Introduction
    1. explain the ICAO requirements for data set provision and updates (6.3.3.1/2/3)
    2. explain that in AIXM the TimeSlice concept enables coding the temporal validity of the information at feature level
    3. a data set will have its own validity, explain how this is coded as metadata
    4. in addition, AIXM allows to distinguish between baseline values, temporary changes and permanent changes.
    5. This means that amendments to data sets can be provided in several ways. Proposed approach:
      1. Baseline DS - contains all and only Baseline TimeSlices that are valid or start their validity at the start of validity of the data set. No Baselines that end their validity. No Tempdelta, no exceptions (such as Baselines that start their validity a few days after the AIRAC date).
      2. Baseline Differences DS - contains only the differences in the form of BASELINES (new ones and the ones that ended their validity). Optionally, it can include also PERMDELTA TimeSlices for the same purpose, which have the advantage that they can indicate a bit more precisely the location of the change.
      3. Supplementary Differences DS - contains the equivalent of AIP SUP - TEMPDELTA with long validity, New BASELINE with known end of validity. Exceptions from the AIRAC cycle.

Specific requirements for how data sets should be updated are contained in ICAO Annex 15, section 6.3:

       6.3.3.1 Data sets shall be amended or reissued at such regular intervals as may be necessary to keep them up to date.

       6.3.3.2 Permanent changes and temporary changes of long duration (three months or longer) made available as digital data shall be issued in the form of a complete data set or a sub-set that includes only the differences from the previously issued complete data set.

       6.3.3.3 Recommendation.— When made available as a completely re-issued data set, the differences from the previously issued complete data set should be indicated.The purpose of this section is to provide rules and recommendations that harmonise the data sets from a temporal point of view - effective date, validity period, types of AIXM TimeSlice, etc.


When a State starts providing an AIS data set, there will always be a first data set that is complete, in the sense that it includes all the data provided by that State. According to Annex 15, item 6.3.3.2, when changes occur, States have the option to either re-issue the complete data set or to publish an update that contains only the differences. Both options are supported by the AIXM Temporality Concept.

Many traditional AIS clients, such as other State AIS, data houses and flight planning service providers, maintain their own aeronautical databases. Such users are primarily interested in receiving regular updates in order to keep their local data up to date. Therefore, the provision of the differences (new/changed/deleted) as compared to the previous data set issue is considered mandatory.

However, the provision of just a list of differences puts the effort of compiling the actual data set on the next intended user. As update files will accumulate, this tasks risks to become increasingly complex and to alter the integrity of the data set. Therefore the regular provision of a complete/consolidated data set is also considered mandatory. This will provide both a ready-to-use data set and the possibility to verify the completeness of a client database that is compiled from the data set updates.

It shall be also noted that the Annex 15 requirement in 6.3.3.2 implies the inclusion of temporary changes of long duration in the AIS data sets. 

Complete AIS Data Set


Tip
titleRule

For each applicable effective date, a complete AIS Data Set shall be provided comprising for all features that are actually comprised in the scope of the AIS data set:

The TimeSlices with interpretation BASELINE and, if applicable TEMPDELTA, with a validity period of three months or longer, and which:

- are active on that effective date;

become active on that effective date;

- become active before the next regular issue of the AIS Data Set.

     Note: In this context, the term "active" designates any TimeSlice that has its beginPosition at or before the specified date and the endPosition after that date or an indeterminate endPosition.

The diagram to the right indicates the TimeSlices that shall be included in the complete AIS Data Set


AIS Data Set - Baseline Update


Tip
titleRule

As a complement to each complete AIS Data Set, an AIS Data Set - Baseline Update shall be provided, comprising for all features that are actually comprised in the scope of the AIS data set:

- the correction TimeSlices with interpretation BASELINE and, if applicable TEMPDELTA, that have their period of validity ending on the effective date;

- the correction TimeSlices with interpretation BASELINE and, if applicable TEMPDELTA, that have their period of validity ending before the next regular issue of the AIS Data Set;

- the TimeSlices with interpretation BASELINE and, if applicable TEMPDELTA, that become active on the effective date;

- the TimeSlices with interpretation BASELINE and, if applicable TEMPDELTA, that become active before the next regular issue of the AIS Data Set.


The diagram to the right indicates the TimeSlices that shall be included in the AIS Data Set - Baseline Update

AIS Data Set - Delta Update


The Temporality concept can be implemented with either/or BASELINE and PERMDELTA.


Info
titleRecommendation

As a complement to each complete AIS Data Set, an AIS Data Set - Delta Update should be provided, comprising for all features that are actually comprised in the scope of the AIS data set:

- the TimeSlices with interpretation PERMDELTA that are valid on the effective date;

- the TimeSlices with interpretation PERMDELTA that are valid before the next regular issue of the AIS Data Set;

- the TimeSlices with interpretation TEMPDELTA, if applicable, that have their period of validity ending on the effective date;

- the TimeSlices with interpretation TEMPDELTA, if applicable, that have their period of validity ending before the next regular issue of the AIS Data Set;

the TimeSlices with interpretation TEMPDELTA, if applicable, that become active on the effective date;

- the TimeSlices with interpretation TEMPDELTA, if applicable, that become active before the next regular issue of the AIS Data Set.


The diagram to the right indicates the TimeSlices that shall be included in the AIS Data Set - Baseline Update

Additional rules



Tip
titleRule

The effective date of an AIS Data Set shall be clearly indicated through metadata.

Some AIS Data Sets contain, for a large part, data that is subject to the AIRAC cycle rules for predefined effective dates and advanced notification. Therefore, some AIS Data Sets are primarily issued with AIRAC applicability dates.

An AIS Data Set remains valid until the next one is provided by the same authority. However, this can lead to uncertainty on the data user side, in case there is no new AIS Data Set published at the next AIRAC cycle or for a longer period of time. Therefore, it is clearer if an AIS Data Set is published for each regular update date or AIRAC cycle date, even if there are no changes.

Tip
titleRule

An AIS Data Set that includes changes under the AIRAC system shall be clearly identified through the use of the acronym “AIRAC” in the metadata.

An AIS Data Set is typically provided no more than 28 days in advance. An eventual non-AIRAC AIS Data Set might be provided within the period of 28 days. Obviously, the changes included in the non-AIRAC update need to be merged in the previously issued data AIS Data Set for the next AIRAC date. The same difficulty was encountered by many States when providing an Electronic AIP (eAIP). Based on their experience, the simplest solution is to schedule the non-AIRAC updates to be also effective on the AIRAC cycle dates (and not at the start or in the middle of the month, as it used to be the case for paper AIP amendments). Thus, the non-AIRAC AIS Data Set can include the already provided AIRAC AIS Data Set changes, plus the additional non-AIRAC changes.Updates outside the AIRAC cycle are possible for data items that are included in the data set and that are not subject to AIRAC, such as phone number, etc. Such non-AIRAC updates exclude elements that are necessary to FMS systems, but they could still be useful for flight-planning operations in ground based systems. A non-AIRAC update would become applicable on the date of publication.

Tip
titleRule

The TimeSlices included in the AIS Data Set shall correspond to one of the AIXM Temporality use cases.