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Why necessary
The AIXM UML model defines, using UML class diagrams, the information items that are in the scope of the "aeronautical information" domain. This includes definitions of classes, attributes and relationships between classes. For attributes, constraints expressed as lists of values, range of values, pattern are also included in the AIXM UML model. The AIXM XML schema is derived from the UML model and defines elements that correspond to the AIXM model classes, attributes and association role names. The values of XML elements and data types derived from UML attributes are constrained based on the data types defined in the UML model - list of values, data ranges and/or patterns.
More complex constraints, such as dependencies between the values of different attributes (sometimes in different classes), detection of 'out of range' values, mandatory properties for class of objects, etc. are not included in the AIXM UML model and do not appear in the XML Schema. Thus, there is need to document such more complex constraints as "business rules". The aim of providing AIXM Business Rules is to be able to define what is possible or allowed in an AIXM data set, in particular with regard to data values.
Not all the AIXM Business Rules are equally applicable in all communities of AIXM users. The most obvious example are mandatory properties for AIXM features - in a flight planning community, there is no need to include in an AIXM data set the frequency/channel of a navigation aid. On the other side, such attributes are mandatory for data sets provided to an air navigation community. Therefore, the aim of the AIXM Business Rules is to document an exhaustive pool of rules, from which profiles for a particular community can be extracted
Executive summary
This documentation defines the AIXM 5.1 "business rules" concept, in particular how the rules are modelled and how they are provided to system developers. Such rules can be used to verify if AIXM XML data sets, which are already syntactically valid (against the AIXM XML Schema), are also semantically correct and can be used in confidence for a particular application.
The objective of the AIXM Business Rules project is to provide, in a standard format, an exhaustive set of operational constraints that may apply to aeronautical data. This includes requirements for minimal data properties, data quality and any other operational constraints, such as the rules for frequency pairing for VHF navaids, etc.
A second objective is to captureThis also includes structural rules that are specific to the AIXM context (such as the relation between the type of TimeSlice and its validity period, etc.) and which are not
enforced inenforceable with the AIXM XML schema.
While the objective is to provide an exhaustive set of rules, only a subset of the rules might be relevant and needs to be enforced/checked for a particular application. For example, a rule that concerns mandatory feature properties might indicate that the frequency of a navaid is a required value. While for a charting or air navigation support application this is a necessary constraint, for a flight planning application this is not necessary. Therefore, profiles (subsets) of the AIXM Business Rules will be proposed for particular applications and/or AIXM user communities.
The Semantics of Business Vocabulary and Rules (SBVR) standard is applied for writing the AIXM business rules, in relation with the AIXM UML logical data model. This means that the AIXM classes and their properties (attributes and associations), together with their definitions and data types, provide the the "business vocabulary" that is used as the basis for the definition of the AIXM business rules.
This documentation provides an 'SBVR profile', which is tailored to the AIXM needs and which is documented as a number of concepts and conventions applied in the writing of the AIXM business rules. This documentation is not intended as an exhaustive introduction in SBVR; it is mostly a "primer" document, giving the essential elements that need to be understood in order to:
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The actual set of AIXM Business Rules is provided on the AIXM Web site. |
Note concerning the previous versions and the use of Schematron
Previous versions of the AIXM Business Rules (up to and including version 0.7.2) used to include Schematron code for a part of the rules. This was done for two reasons:
- in order to verify that the SBVR description of the rule is sufficiently clear and unambiguous in order permit its actual implementation as software code;
- as proof of concept, to show how an AIXM data set could be verified against the business rules using software readily-available.
However, the Schematron code was missing for many rules and even where it existed it was no always maintained when the rules were modified. The code was also not optimised for large AIXM data sets, which could result in performance issues. Therefore, starting with version 0.8 there is no Schematron code included with the AIXM Business Rules set. It might come back in a future release if there is a real need to that and if possible to find resources for properly maintaining it.
An AIXM Business Rules Profile was defined for the data input to the European AIS Database (EAD). Additional profiles are being defined for the ICAO digital data sets (AIP, obstacles, etc.) and for Digital NOTAM.
Rules grammar - two versions
Version 1 - until 2023
The initial approach for the AIXM 5.x business rules was based on SBVR as rule language and on the AIXM UML model as business vocabulary. This was applied for the provision of the AIXM Business Rules for the European AIS Database (EAD), until end 2023. This approach is documented here: Version 1 (until 2023)
Version 2 - starting in 2024
The objective of the "new SBVR syntax" is to maximise the potential for automatic generation of data set validation code from the AIXM Business Rules. This is achieved through the following changes in the AIXM Business Rules approach:
- a strict AIXM business rules grammar
- use of the AIXM XML elements and attributes as vocabulary (SBVR noun-concepts) instead of the classes/properties/associations from the UML model;
This new approach is documented here: Version 2 (starting in 2024)
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