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Context Representation Transformations

In today's interconnected digital ecosystem, the seamless exchange of information between diverse systems is more critical than ever. A fundamental obstacle to achieving true interoperability lies in how different systems represent context information about concepts. Some systems embed this context directly within the terminology, using codes with rich, nuanced meanings. Others represent context through their information models, structuring data to convey context via relationships and attributes. This disparity creates a landscape where data exchanged between systems may lose its intended meaning unless carefully transformed and interpreted.

This chapter focuses on the strategies and methodologies for implementing transformations between these heterogeneous models. We will delve into the technical challenges of mapping context from terminologies to information models and explore practical solutions to bridge these differences. By examining real-world scenarios and leveraging interoperability standards, we aim to equip you with the knowledge and tools necessary to ensure that context is preserved and accurately conveyed during data exchange. Understanding these transformation processes is essential for developers, architects, and stakeholders striving to enhance interoperability and achieve consistent, reliable communication across varied systems.

Example of a transformation from a "Situation with explicit context" concept to a FHIR FamilyMemberHistory Resource information model

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Figure 6.3-1:

FHIR and SWEC Comparison

In the context of this SNOMED implementation guide, we have chosen to use the FHIR context model as an example of an information model for several reasons. FHIR is a widely adopted standard in the healthcare industry for exchanging electronic health records and related data. Its modular and extensible design makes it an ideal candidate to demonstrate how context information can be represented outside terminologies like SNOMED CT.

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Clinical Findings with Context vs. FHIR Resources

The following table maps SNOMED CT “Situations with Explicit Context” subhierarchies to relevant FHIR resources, showing how clinical context is represented across terminology and information models.

SNOMED CT Situation (Subhierarchy)
FHIR Resource
Domain
Context
Subject
Temporal Context

  • Where FHIR Resource is listed as N/A, there may be no direct mapping in the base FHIR specification.

  • Context properties such as subject and temporal frame help clarify how the SNOMED concept aligns with FHIR resource attributes like subject, status, or effective[x].

The table below maps specific types of Situations with Explicit contexts to specific FHIR resources and states the associated context properties

As seen in the previous table, depending on the type of context represented in the SWEC concept, it can be transformed into a Condition or Observation resource. Here, we provide some examples of values for different key elements.

FHIR Element Name
FHIR Element Value
SNOMED Attribute
SNOMED Value
FHIR Element Name
FHIR Element Value
SNOMED Attribute
SNOMED Value
FHIR Element Name
FHIR Element Value
SNOMED Attribute
SNOMED Value
FHIR Element Name
FHIR Element Value
SNOMED Attribute
SNOMED Value

160266009 |No family history of clinical finding (situation)|

(None / N/A)

Clinical finding

Known absent

Person in the family

All times of past

1260502004 |History of event in life of subject (situation)|

Condition

Event

Known present

Subject of record

In the past

373572006 |Clinical finding absent (situation)|

Observation

Clinical finding

Known absent

Subject of record

Current or specified time

History Events with finding context

Observation

Event

Known absent

Subject of record

Current or specified time

373573001 |Clinical finding present (situation)|

Condition

Clinical finding

Known present

Subject of record

Current

443859009 |Possible clinical finding (situation)|

Condition

Clinical finding

Known possible

Subject of record

Current or specified time

443938003 |Procedure carried out on subject (situation)|

Procedure

Procedure

Done

Subject of record

Current or specified time

416237000 |Procedure not done (situation)|

Procedure

Procedure

Not done

Subject of record

Current or specified time

439763000 |Procedure on family member (situation)|

Procedure

Procedure

—

Person in the family

Current or specified time

Associated finding

<< Clinical finding

Associated finding

<< Clinical finding

Finding context

Known absent

Procedure context

Done

Procedure.category

Surgical

(Ancestor)

Surgical procedure

Procedure.reasonCode

Disease

Has focus

<< Clinical finding

Procedure.bodySite

Body site

Procedure site - direct

<< Anatomical structure

417662000 |History of clinical finding in subject (situation)|

Condition

Clinical finding

Known present

Subject of record

In the past

416471007 |Family history of clinical finding (situation)|

FamilyMemberHistory

Clinical finding

Known present

Person in the family

Condition.clinicalStatus

inactive

Temporal context

In the past

Condition.code

Condition.clinicalStatus

active

Temporal context

Current

Condition.code

Observation.code

Clinical finding

Associated finding

<< Clinical finding

Observation.value

Procedure.code

Procedure

Associated procedure

<< Procedure

Procedure.status

Notes

Clinical Findings with Context vs. FHIR Resources

Attributes vs. FHIR Resource Elements

Condition Resource vs. |History of clinical finding in subject|

Condition Resource vs. |Clinical finding present|

Observation Resource vs. |Clinical finding absent|

Procedure Resource vs |Procedure Done|

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Current or past

Clinical finding

Clinical finding

Known absent

Completed

Transformations between SWEC and FHIR

Transforming information between the SNOMED concept model and a FHIR representation is a clear use case for interoperability or analytics. Creating a set of rules to reproducibly perform these transformations safely in real-world scenarios is possible.

We represent these rules as a decision table to offer a clear and structured approach to handling the heterogeneity between terminologies and information models. Although the list provided is not exhaustive and serves only as an example, it effectively demonstrates the critical considerations and steps involved in the transformation process. This approach helps readers understand not just the theoretical aspects but also the practical implementation of transformation rules, enabling them to apply similar strategies within their own systems to achieve seamless interoperability.

Parent concepts in the Situation hierarchy
Context
Subject
Temporal
FHIR Resource
Presets for information model elements

417662000 |History of clinical finding in subject (situation)|

Known present

Subject of record

In the past

Condition

clinicalStatus = inactive

416471007 |Family history of clinical finding (situation)|

Known present

Person in the family

Current or past

FamilyMemberHistory

To further illustrate the practical application of these transformation rules, we have developed a demonstration tool that performs real-time conversions from SNOMED CT to FHIR. This tool serves as a concrete example of how context information can be effectively translated between different models using a similar set of rules. It is open source, and the code is publicly available for anyone to review, use, or modify.

https://ihtsdo.github.io/sct-implementation-demonstrator/#/context

Figure 6.3.2-1: A screenshot of the realtime transformation demonstration site

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Example of a set of transformation rules from SNOMED Situations to FHIR Resources

relationship = << 303071001 |Person in the family (person)|

1260502004 |History of event in life of subject (situation)|

Known present

Subject of record

In the past

Condition

clinicalStatus = inactive

373572006 |Clinical finding absent (situation)|

Known absent

Subject of record

Current or specified time

Observation

observation.code = associated finding observation.value = known absent

373573001 |Clinical finding present (situation)|

Known present

Subject of record

Current

Condition

verificationStatus = confirmed

443859009 |Possible clinical finding (situation)|

Known possible

Subject of record

Current or specified time

Condition

verificationStatus = unconfirmed