Working towards the next version of the SWIM Supporting Material

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The opportunity

It is not clear in which order to read traces when there are more than one in a single semantic correspondence statement. Some traces are, in fact, qualifiers of other traces.

Is it possible to:

  • somehow differentiate the traces and
  • apply a reading order?

Discussion

The discussion has been split into parts to make easier to follow.

Assumptions

The SWIM Information Definition Specification assumes that we are not yet in an environment that is fully supported by semantic technologies. Therefore, humans are the more realistic target for the semantic correspondence statements. This leads to the following statements about traces:

  • The traces are to be read by humans but may be read by machines (machine processable).
  • The traces are to be created and inspected by humans. There is nothing to stop machines creating the mappings but any such mappings will still need human inspection.
  • The maintenance and migration of traces can be managed by machines (or humans) based on scripts.

The need for a machine readable list of mappings has been recorded in the AIRM CCB to ease the migration of mappings between versions of the AIRM. This can be summarised as the need for "machine processable" maintenance of traces.

Different types of traces

The table below outlines the names and definition to be used for the different types of trace. The names are inspired by the words from the SWIM Information Specification's requirements. This approach makes it clear which requirement is being satisfied by the trace.

Trace nameDefinitionRequirementTrace required
"information concept" tracetrace from the information concept in the information definition to the AIRM concept that has an equivalent or wider meaningSWIM-INFO-016 Mapping of information conceptsrequires one concept trace
  1. "data concept" trace
  2. "data type" trace
  1. trace from the data concept in the information definition to the AIRM concept that has an equivalent or wider meaning
  2. trace to the data type in the AIRM that has an equivalent or wider meaning
SWIM-INFO-017 Mapping of data concepts

requires one concept trace and one data type trace

"narrowing" tracetrace to an AIRM concept to fully describe the narrowing of the concept being mappedSWIM-INFO-018 Additional traces to clarify the mappingallows any number of additional narrowing traces

Source and target of traces

The Interoperability Architecture provides good guidance on the best place to start when looking to establish a semantic correspondence. Basically, the best place to start is usually the adjacent box within the grid.

The usual start point depends on the type of information definition being traced.

Type of information definitionBest place to start
information exchange requirements

The best place to start is the AIRM Conceptual Model.

However, information exchange requirements can vary in the level of detail included. Therefore, if no suitable AIRM concept is found in the AIRM Conceptual Model, the AIRM Logical Model may be useful.

For the most part, it is expected that these types of trace fall under requirement 16. Narrowing traces (requirement 18) can be added as needed. It is usual that these trace to the same part of the AIRM as the "main" trace.

The specification doesn't rule out mapping to the AIRM Contextual Model but this is not a good practice.

service message /

information exchange model

Service messages and information exchange models can include concepts that are of different level of granularity. For example, they may contain standardised "messages" such as NOTAM and METAR. They also contain more atomic concepts such as "Aerodrome" or "Airspace". These in turn may have attributes/properties such as the "ICAO location indicator".

Although it is difficult to give generic advice that is applicable in all cases, the following guidance is applicable:

  • Standardised "messages" are captured in the AIRM Conceptual Model. Mapping to these tend to fall under requirement 16. If no suitable AIRM concept is found in the AIRM Conceptual Model, the AIRM Logical Model may be used.


It is an AIRM design decision to allow messages to be added at the service level. The AIRM Logical Model does not impose any message structure. However, the existence of the standardised messages is captured as part of the operational language in the AIRM Conceptual Model.

  • The best place to start when mapping "atoms" is the AIRM Logical Model. Concepts of this nature may, for example, be modelled as classes in UML models. These tend to fall into requirement 16 as they do not have a "data type" associated with them. If no suitable AIRM concept is found in the AIRM Logical Model, the Conceptual Model may be used.
  • Attributes/properties will have a "data type" and therefore fall within requirement 17, requiring both types of trace to be created. If no suitable AIRM concept is found in the AIRM Logical Model, the Conceptual Model may be used

The AIRM has internal traces that are inherited by any mapping.


Narrowing traces (requirement 18) can be added as needed. It is usual that these trace to the same part of the AIRM as the "main" trace.

The specification doesn't rule out mapping to the AIRM Contextual Model but this is not a good practice.

Reading order of traces

General reading order is:

  1. "information concept" trace
  2. "narrowing" traces (0..*)

or

  1. "data concept" trace
  2. "data type" trace (1)
  3. "narrowing" traces (0..*)

All traces have an AND relationship.

The following rules apply to the traces:

  • The root trace is mandatory. This is either an  "information concept" trace or a "data concept" trace.
  • A "data type" trace is mandatory when the root trace is a "data concept" trace.
  • "Narrowing" traces cannot exist in their own right.

How many traces are sufficient/enough?

The important thing is to add sufficient traces to make sure the semantics are understood. There is no need to add more traces.

If you find that too many traces are required to ensure that the semantics are understood, there may be a problem somewhere in fully understanding the meaning of a concept. In that case a change may be needed to the information definition and/or the AIRM.

Level of semantic correspondence

Advanced users may like to add extra detail concerning the level of semantic correspondence achieved. The requirements talk about "equivalent or wider meaning". The table below contains the old AIRM Rulebook names and the skos equivalents.

Definition being traced to is...

Annotations that can make this more explicit

in SESAR documents


in skos

Equivalent
  1. ExactCopy: Definition of concepts in the information definition and the AIRM are exact copy of each other.
  2. SyntacticallyEqual: Definitions are only different due to syntax corrections (grammar, spelling) but are otherwise equivalent.
  3. Rewritten: The definition of the concept in the information definition has been rewritten to reflect information definition specificity. However, the meaning is the same, i.e. the definition still describes exactly the same concept as the AIRM.
  1. skos:exactMatch: is used to link two concepts, indicating a high degree of confidence that the concepts can be used interchangeably across a wide range of information retrieval applications.
  2. -
  3. skos:closeMatch: is used to link two concepts that are sufficiently similar that they can be used interchangeably in some information retrieval applications.
WiderSpecialised: The definition in the information definition is a special case of the definition found in the AIRM.skos:narrowMatch:
used to state a hierarchical mapping link between two concepts.

The skos names are preferred. Skos has rich support in semantic technologies. However, SESAR documents use slightly different names based on the old AIRM Rulebook.

Both options are therefore valid.

We only need narrowing traces if the main trace is "specialised" or "narrowMatch"

Traces cannot be annotated as "generalised" as this breaks the requirement.

Annotating traces

It is possible to add further notes to the mapping (the container for one or more trace). This comes in handy when e.g. tracing legacy interfaces that have data type constraints leading to loss of Information.

Representing traces in XSD

The table below gives two alternatives for recording the traces in XSD.

Using element names is the preferred option as it can be used more easily in rules. The element name contains semantic hints even if the attributes are not added.

However, the attribute option is also supported as there are a lot of traces developed that do not use element names. Support for this option should be deprecated in the future.

Trace nameElement nameAttribute
"information concept" trace<informationConceptTrace><trace keyword="informationConceptTrace>
  1. "data concept" trace
  2. "data type" trace

<dataConceptTrace>

<dataTypeTrace>

<trace keyword="dataConceptTrace>

<trace keyword="dataTypeTrace>

"narrowing" trace


<narrowingTrace>

<trace keyword="narrowingTrace>

Full example

If we apply all of this:


<xs:annotation>
  <xs:documentation>
    <semanticCorrespondence>
      <mapping>
        <note>loss of info because of legacy</note>
        <informationConceptTrace degree="specialised">-AIRM unique identifier-</informationConceptTrace>
        <narrowingTrace>-AIRM unique identifier-</narrowingTrace>
      </mapping>
    </semanticCorrespondence>
  </xs:documentation>
</xs:annotation> 

or:

<xs:annotation>
  <xs:documentation>
    <semanticCorrespondence>
      <mapping>
        <note>loss of info because of legacy</note>
		<trace type="informationConceptTrace" degree="specialised">-AIRM unique identifier-</trace>
        <trace type="narrowingTrace">-AIRM unique identifier-</trace>
      </mapping>
    </semanticCorrespondence>
  </xs:documentation>
</xs:annotation> 



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