All encoding scenarios include the possibility to provide free text notes. These are encoding in AIXM 5 as Note objects, associated with the TimeSlice that is created for the Event, as indicated in the general AIXM coding rules for Note. Each scenario includes further details about the encoding of such Note items, in particular with regard to the values of the propertyName and purpose attributes.

In addition, a limited number of AIXM features have properties with text content, such as InstrumentApproachProcedure.instruction. When used in Digital NOTAM, the same character set and text formatting rules as for annotation.Note apply to these text elements.

Note: in the current version of the Digital NOTAM Specification, no such "instruction" property is used yet.

Maximum length

The maximum length of a Note text (translatedNote.LinguisticNote.note property) in AIXM is 10 000 characters. This largely exceeds the size of a normal NOTAM. In addition, information provided by Notes should be concise and easy to present in full in a limited space. Therefore, each Note text shall be limited to 250 characters.

Overwrite baseline notes

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

Annotations shall be limited to the use of the character set specified in the Character set.

Formatting rules

General rules for usage of upper case characters

The first letter in a sentence.
Each first letter of a name (such as 'Brussels South').
Location indicators.
Designators, such as five-letter ICAO designators for waypoints, navigation aid designators, route/SID/STAR designators, airspace designators, etc.
AIXM 5.1 Limitation

In AIXM 5.1(.1), all names are just in upper case. This is a limitation inherited from AIXM 4.5 where it was introduced exactly for facilitating the use of feature names in AFTN messages (such as NOTAM). This limitation will be eliminated in AIXM 5.2. An AIXM Change Proposal was approved by the AIXM CCB for this purpose: [AIXM-391] Allow lower case in names

General rules for usage of lower case characters

Consecutive text after the first letter in a sentence.
Abbreviations, except those specifically mentioned to be written otherwise (see below).
Spelled out abbreviations and acronyms, with the exception of the first letter for defined acronyms (for rules on spelled-out abbreviations and acronyms, see below).

Special situations that require a mix of uppercase and lower case characters

Unit of measurements shall be spelled in accordance with SI units, https://physics.nist.gov/cuu/Units/units.html, except where the aviation practice is different (such as for the unit used for "seconds").

Rules for formatting acronyms and abbreviations:

Specific rules are defined for formatting abbreviations and acronyms in digital NOTAM text. These rules consider usage of upper and lower case together with rules for spelled-out text of abbreviations and acronyms, defining:

Abbreviations and acronyms that shall be spelled out, and usage of lower/upper case of the spelled-out text.
Abbreviations and acronyms that shall be kept and usage of lower/upper case of the abbreviated text.
Acronyms that shall be spelled out and with the first letter of each word in upper case.

The principle is that abbreviations/acronyms that are not commonly used, not included in ICAO Doc 8400 and/or may be subject to misunderstanding shall not be used, but instead be spelled out (e.g. use 'Area Chart' instead of "ARC").
The categories that fall under the defined rules are summarized in the table below.

Appendix A provides the detailed digital NOTAM format of the ICAO Doc 8400 abbreviations and acronyms following these rules.

Rules	Categories
*Abbreviations* that shall be *spelled out* and written in *lower case*. ICAO Doc 8400 provides abbreviations for words that are already short, such as 'closed", available', 'active'. These words do not need to be abbreviated since the spelled out format does not significantly add to the length of the message. The spelled out text facilitates the understanding of the message.	short words specified locations, e.g. above, beyond, before, under, abeam, between, below, behind, adjacent, across, centred, within. cardinal points and their combinations, except when used after coordinates in lat/long. colours lighting types, except ALS (Approach Lighting System) abbreviations not included in ICAO Doc 8400.
*Abbreviations* and *acronyms* that shall be *kept* and spelled in *UPPER CASE*. Certain abbreviations and acronyms are so well known in the aeronautical domain that are regarded as true words, and shall therefore be kept and also be spelled in upper case.	air traffic services types RWY, TWY, THR, AWY aerodrome, heliport navigation and landing aid types airspace types months and days com and surveillance systems routes codes for operating hours level indicators (AMSL, GND, SFC) certain aeronautical chart types …and more..
*Abbreviations* and *acronyms* that shall be *kept* and spelled in *lower case. In normal document text in the aeronautical domain, we are used to see certain abbreviations and acronyms spelled in lower case. The same principle applies also for the Digital NOTAM text. Example: "The most looked up abbreviations in our online dictionary are i.e.* and e.g., probably because they are often confused for one another. You can use the e.g. and i.e. abbreviations both inside and outside the parenthesis." ´The purpose of this document is to provide templates for the Item E for some frequent issued NOTAM types, e.g. closed RWY, active restrictions etc." "Closed for acft heavier than…"	certain often used acronyms/abbreviations
*Acronyms* that shall be *spelled out* and with the *first letter* of each word in *upper case* (also known as "title case") Do not stress capital letters in normal fluent text, unless seen justified for certain terms, such as "Minimum Sector Altitude", "Temporary Reserved Area". If the acronym is rarely used or un-known (e.g. "SD" for "standard deviation'), the spelled out words shall not capitalize the first letters of each words forming the acronym; instead, each word shall begin with lower case.	airspace, areas (Temporary Reserved Airspace) altitudes types (e.g. Minimum Sector Altitude) certain aeronautical chart types Approach Lighting System

Examples of usage

Digital NOTAM text examples, in which the rules stated above are applied:

ATS operating hours changed as follows: 01 03 05 1000-1600 02 04 06-31 0800-2200.
Due to the unavailability of edge lights.
SAR exercise involving military parachute jumping and flares

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