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Need for information definitions




Exchanged information shall be documented in an information definition.


The requirement for information definitions is essential in order to facilitate semantic interoperability. Without information definitions, there are no resources to allow the meaning of the information to be clearly defined, understood and harmonised between stakeholders.




Example: Standardised information exchange models such as the Aeronautical Information Exchange Model (AIXM) [RD10], the Flight Information Exchange Model (FIXM) [RD 11], the Weather Information Exchange Model (WXXM) [RD 13] and the ICAO Meteorological Information Exchange Model (IWXXM) [RD 14].

Example: Descriptions of information exchanged by services.

Example: Data catalogues used to list details on the exchanged information.

Example: Information exchanges captured as part of a business process model.

Level of Implementation



The specification gives examples of types of information definitions:

  • standardised information exchange models
  • descriptions of information exchanged by services
  • data catalogues
  • information exchanges captured as part of a business process model

The following section gives an overview of these.

Standardised information exchange models

Standardised information exchange models include:

  • Aeronautical Information Exchange Model (AIXM)
  • Flight Information Exchange Model (FIXM)
  • Weather Information Exchange Model (WXXM)
  • ICAO Meteorological Information Exchange Model (IWXXM)
  • Aerodrome Mapping Exchange Model (AMXM)

They are agreed and published by a particular community of interest. There may be multiple versions of an exchange model e.g. IWXXM 1.1 was used by the SESAR programme but a v2.1 is now available and v3 is in pre-operations.

The exchange models listed above relate to three ICAO business domains (aeronautical, weather and flight information). However, other exchange models exist.

A service description may refer to one of these exchange models in order to define its payload.

The figure below provides an extract of the AMXM XML schema. It details "element name", "documentation" and "type" information.

Description of information exchange by services

Services are used to exchange information. Often, the service makes use of a standardised information exchange model as the format for the information exchange. However, other services will develop a more particular payload model. This can be done in the Unified Modeling Language (UML) as given in the figure below.

The figure is taken from a service description for a service exchanging METAR information. It shows the names and definitions of the "EntityItems" that will form the exchanged information.

Data catalogues

Data catalogues are used to list details on the exchanged information. They are often used as a way of agreeing the information that is to be captured and exchanged as part of a publication process. The figure below is taken from the ICAO PANS-AIM Data Catalogue. It is in tabular format and details "subjects", "properties", "types" and their "descriptions". A data catalogue can contain many more items such as requirements on the accuracy of the data to be collected.

Information exchanges captured as part of a business process model

Business process modelling is a key art the service oriented approach. It is used to identify information exchange requirements, including the names and definitions of the elements being exchanged throughout the process.

Publication and management of information definitions

This requirement says nothing about how to publish and manage information definitions. These concerns are not in the scope of the specification.

However, the need to make information definitions discoverable and to manage them properly is well acknowledged. It is therefore hoped that an information definition is open and accessible to the wider community and managed/governed by a well-established group.

Verification Support


Check that:

[  ] There is an information definition. 

[  ] The information definition covers all of the information as defined in the scope statement.


  1. The information definition can be a standalone document or embedded into another document such as a service description.
  2. The information definition can be made up of a set of documents.
  3. The scope statement contained in the information definition helps to answer this check.


Example information definitions are:

A fictional example is available to show how the requirements could be satisfied by an XML Schema file and in a Data Catalogue.

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