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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 startTrace name
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 there, the AIRM Logical Model may also be useful.

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

"information concept" trace
service message

The best place to start is the AIRM Logical Model.

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

Classes have one trace - 016

Attributes have two traces - 017

"data type" trace is dependent on "data concept" trace.

If no suitable AIRM concept is found there, the Conceptual Model may be used for the "data concept" trace. 

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

Note: AIRM has internal traces that are inherited by any mapping.

  1. "data concept" trace
  2. "data type" trace

Clarifying traces should be in the same model as the trace being qualified.



"clarifying" trace

Reading order of traces

Structure of traces - capture the dependencies between the types of traces. Can't have an "additional trace" alone or "data type" trace. The root trace is mandatory. Need to add these rules in the best practice.

see struts from programming languages

General reading order is:

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

or

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

All traces have an AND relationship.

"narrowing" trace instead of "additional" trace


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 explicitor 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.narrowMatch:
used to state a hierarchical mapping link between two concepts.

We could allow both columns with namespace identifiers - codelist entry. Could even map to an URL to give the word.

skos is preferred but SESAR legacy is still supported.

We only need additional traces if the main trace is "specialised"

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

Annotating traces

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

Representing traces in XSD

How should the different traces be represented in the XSD examples we use? The table below gives two alternatives.

If this is a best practice, the attribute option is probably preferable - the attribute can be optional and the name of the element is always <trace>

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>

"additional" trace


<additionalTrace>

<trace keyword="additionalTrace>

Full example

If we apply all of this:

element names are preferred. It can be used more easily in rules.

contains some semantic hints even if the attributes are not added.

see if "degree" has a skos name instead.

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

or:

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

Example of tracing exercise

However it should be consistent with the information given at the AIRM homepage. Links to the according pages will also help.

This is probably handled as a separate activity after the current task is completed.

Background

Existing qualifier names

Different artefacts have used different trace "qualifiers".

Example 1

  1. "Data Traces", which, for the case of SWIM-INFO-017, refer to the Data Type constraints. They must be unique, and may already also contain the full definition (as the best matching AIRM concept with the correct data type constraint will be chosen), so they are logically first in line.
  2. "Definition Traces" which point to the comprehensive or even normative definition (when available) or to the best matching wider AIRM concept (in both SWIM-INFO-016 and SWIM-INFO 017). They must be present and must be unique, so they are next in line (top of the line for SWIM-INFO-016 actually).
  3. "Context Traces" that add qualifiers (i.e. implement SWIM-INFO-018). These are optional, and their order should not have semantic significance.

Example 2

The Donlon example at https://ext.eurocontrol.int/swim_confluence/display/SWIM/Donlon+TOBT+Setting+Service+Description#DonlonTOBTSettingServiceDescription-InformationDefinition is almost the same. It uses:

  1. AIRM Semantic Trace
  2. AIRM Definition Trace. This seems to be in line with what is mentioned above.
  3. AIRM Context Trace. This appears to add the qualifiers as mentioned above.

Example 3

Looking at the ISRM (Information Service Reference Model) it has:

  1. Main CLDM mapping. The mandatory and unique CLDM mapping indicating the AIRM element having the type of data as the OuA construct. E.g. a “time” for TSAT;
  2. Context CLDM Mapping. One or more optional additional CLDM mappings helping achieving a more accurate semantic definition by giving more context to the main CLDM mapping. E.g. the “TARGET” planning status for TSAT;
  3. IM Definition Mapping. An IM mapping allows referencing a unique IM element containing a normative definition (typically from ICAO) for the OUA construct. Can be optional or mandatory depending on contexts as explained in next chapters.

Example 4

EUROCAE ED-254.

The mappings to the AIRM have the following keywords:

  1. SemanticTrace
  2. DefinitionTrace
  3. ContextTrace (which can be further defined as ContextTrace_1, ContextTrace_2, etc)

Keyword: DefinitionTrace.

Value: URN of an AIRM information or data concept

Usage Notes: This will normally point to a resource in the AIRM Information Model, i.e. an AIRM information concept. However, occasionally (e.g. when mapping the definition of certain containers), it may necessary to refer to the definition part of a (CLDM) data concept. In this case, the data type of the AIRM trace target is not part of the trace semantics.

Keyword: SemanticTrace

Value: URN of an AIRM data concept

Usage Notes: When there is no accompanying DefinitionTrace, it is understood that both SWIM-INFO-016 and SWIM-INFO-017 are implemented by this trace (see note on SWIM-INFO-017)

Keyword: ContextTrace / ContextTrace_n

Value: URN of an AIRM information or data concept

Usage Notes: The first form is the standard.  When more than one context traces is required on an element, the second form is used. The EUROCAE document does not formally associate business semantics with data entities, i.e. all data entities are implicitly traced to “OutOfScope: container”. The mappings of individual data fields are therefore self-contained, there is no “trace cascading”.

How many qualifiers

Can’t we survive on:

2 categories:

  • “trace” (1 or more to either AIRM-CM or AIRM-LM; note that the URN shows whether CM or LM)
  • “trace_qualifier”

In the schema trace and trace_qualifier could then be differentiated.

2 best practices:

  • Order best practice: “widest first”
  • Qualifier best practice: “Trace qualifier directly after qualified trace”

Adding notes to mappings

It is maybe worth noting here that sometimes you want to put a comment on a mapping, so I am allowing this as an extra annotation. This comes in handy for example when tracing legacy interfaces that have data type constraints leading to loss of Information.


Perhaps we need to look at what "aspects" of the AIRM model are mappable to first -  and also possible the level of alignment (eg exact, broader, etc aka SKOS-like).

From old AIRM rulebook

AIRM_Rule 60

The 'Definition:Adapted' AIRM::TaggedValue shall be completed in order to indicate the level of semantic correspondence with the source definition. The list of values is:

  • ExactCopy: Definition of source and target are exact copy of each other.

  • SyntacticallyEqual: Syntax corrections (grammar, spelling)

  • Rewritten: The definition has been rewritten for improved quality. The meaning is the same, i.e. the definition still describes exactly the same entity as the target definition.

  • Specialised: Source definition is a special case of the target definition.

  • Generalised: Source definition is a generalised case of the target definition.

AIRM_Rule 116

A data or information construct is considered to be in semantic correspondence with the AIRM if one of the following conditions holds:

  1. The definition of the construct is an exact copy of the definition of a specific AIRM element, or it is syntactically equal, or is rewritten or is specialised as described in AIRM_Rule 60.

  2. It can be demonstrated that the definition of the construct can be decomposed into several elementary concepts, each corresponding to an AIRM element as per previous bullet. This decomposition must be comprehensive, i.e. cover all parts of the definition.

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