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AIXM supports the encoding of schedules that contain both repetitive time periods and occasional occurrences. The coding guidelines for schedules/timetables can be found in: AIXM Coding Overview - Common Coding Rules - Common coding patterns. These general coding guidelines for schedules the ICAO Data Sets include general coding rules for Schedules [PWS]. These are also applicable to Digital NOTAM Events. However, based on the limitations specified in the OPADD document, only a subset of schedules is allowed for temporary events published by NOTAM. The limitations are described further down , more restrictive rules apply to NOTAM schedules, such as excluding the possibility to use 'HOL' and other special dates. These limitations lead to a smaller number of coding patterns for Digital NOTAM Event schedules, which are presented in this section.
Limitations
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Supported schedules
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- daily schedules;
e.g. "daily from 09:00 to 17:00"; - date based schedules, including "on date" and "date range" options;
e.g. "1/10 09:00-15:00 and on 3/10 10:00-12:00"; - weekday days of the week based schedules, including "on weekday", or "from weekday...to weekday" options;
e.g. "every Monday from 13:00 to sunset".
The information items that may occur in the definition of schedules are identified in the diagrams described in the Common Coding Rules - Common coding patterns, section Common coding patterns. For use of "daily", "on date" and "date ranges" templates please refer to Common coding patterns - "Daily" schedules diagram. For use of "on weekday" and "from weekday...to weekday" please refer to Common coding patterns - "Weekday" schedules diagram. Each diagram is accompanied by the corresponding graphical elements explanation.
Not supported schedules
Combining different schedule types in a single NOTAM is forbidden. It is considered that such combined schedules could become too complex for being understood and would have a high potential for providing conflicting information. For example, "daily 0900-1700 and each MON 1900-2300" would not have a clear meaning. Is the schedule for Mondays just 1900-2300, or is it both 0900-1700 and 1900-2300? Therefore, such combined schedules are not supported.
Note that the concept of "weekday ranges" (such as "MON-WED") is also not supported in this specification. However, the automatic NOTAM generation rules for item D ensure that a set of consecutive weekdays with a similar start/end time will generate a "weekday range", according to the OPADD recommendations. This does not exclude implementing an HMI that allows the input of weekday ranges, for efficiency reasons. They will have to be converted into individual weekday records in AIXM.
UML class diagrams representation
The limitations identified above correspond to a subset of the general AIXM model for schedules. In the following diagram, classes and properties highlighted with orange color identify the part of the AIXM UML model which may be used for Digital NOTAM coding:
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The data type or the list of allowable values associated with each Timesheet attribute in a Digital NOTAM encoding are marked in orange in the following diagram:
HMI recommendations
Some schedules may be relatively complex and this may lead to difficulties for the operator when trying to get the global picture of what is being encoded. Based on the experience gathered in this area through trials and previous projects, it is recommended that the HMI for schedules encoding enables both:
- "forms based" input - where the operator enters values in predefined fields, and
- "text based" input - where the operator types directly a textual description of the schedules and the application automatically decodes that into structured data; the text based input is expected to be used for simpler but frequently used schedules;
When the form based input is used, the application should generate a text based description of the schedule in real time, in the form that it would appear in a NOTAM item D or E. This would give confidence to the operator that the schedule was correctly encoded.
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Tempdelta - additional versus complete hours
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According to the AIXM Temporality document, a TEMPDELTA shall contain a complete description of the operating times.
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The data encoding rules provided in this section shall be followed in order to ensure the harmonisation of the digital encodings provided by different sources. These rules shall be used as complementing the General coding rules for Schedules defined in AIXM Coding Overview - Common Coding Rules - Common coding patterns. In case of contradiction, the rules described below are superseding the general ones.
The information items that may occur in the definition of schedules are identified in the diagrams described in the Common Coding Rules - Common coding patterns, section Common coding patterns. For use of "daily", "on date" and "date ranges" templates please refer to Common coding patterns - "Daily" schedules diagram. For use of "on weekday" and "from weekday...to weekday" please refer to Common coding patterns - "Weekday" schedules diagram. Each diagram is accompanied by the corresponding graphical elements explanation.
The compliance with some of these encoding rules can be checked with automatic data validation rules (see next section).
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