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According to the AIXM Temporality rules, the annotation properties included in a TEMPDELTA TimeSlice completely replace the BASELINE annotations. Therefore, any eventual BASELINE annotation that remains valid during the validity of the TEMPDELTA should be included (copied) in the TEMPDELTA.
Character set
The Digital NOTAM concept includes the automatic generation of the ICAO text NOTAM from the digital encoding. As explained in the
The NOTAM message needs then to be transmitted on AFTN networks, which only support a limited character set. As the digital encoding in AIXM virtually allows any Unicode character to be used for example in annotations and remarks, there is a potential risk that unsupported characters appear in the NOTAM text. Therefore, it is necessary to limit the character set used in the various fields of a Digital NOTAM encoding to those that can be unambiguously and without information loss be converted into the AFTN supported character set.
According to the Annex 10 to the ICAO Convention (section 4.1.2.1), the following characters are allowed in NOTAM text messages:
- Letters: ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz
Note: in order to improve the readability of Digital NOTAM, the use of lowercase characters is also allowed in the encoding; they shall be converted into uppercase for NOTAM text generation. - Figures: 1 2 3 4 5 6 7 8 9 0
- Other signs:(hyphen)
- - (hyphen)
- ? (question mark)
- : (colon)
- ( (open bracket)
- ) (close bracket)
- . (full stop, period, or decimal point)
- , (comma)
- ’ (apostrophe)
- = (double hyphen or equal sign)
- / (oblique)
- + (plus sign)
Characters other than those listed above shall not be used in messages unless absolutely necessary for understanding of the text. When used, they shall be spelled out in full.
Restrictions on the character set are already embedded in the AIXM schema for elements such as names, identifiers, etc. For AIXM elements of type annotation, instructions, etc. that are allowed by the AIXM Schema to use any Unicode character it is important that Digital NOTAM applications limit the character set that can be used to the one mentioned above.