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Background
SNOMED CT is a clinical terminology with global scope covering a wide range of clinical specialties and requirements. The use of SNOMED CT expressions in Electronic Health Records electronic health records (EHRs) provides a standardized way to represent clinical meanings captured by clinicians and enables the automatic interpretation of these meanings. SNOMED CT Expression Constraints expression constraints provide a computable rule that can be used to define a bounded set of clinical meanings for the purpose of constraining the contents of a data element in an Electronic Health Record electronic health record (EHR), intensionally defining a concept-based reference set, querying SNOMED CT content in a machine processable way, or restricting the range of an attribute defined in the SNOMED CT concept model.
In some situations, however, the specific focus concepts or values of particular attributes are not known at the time of authoring. In these cases, one or more slots may be used within an expression or expression constraint to create an expression template or expression constraint template (respectively). The slot provides Slots provide a placeholder in the expression or expression constraint, whose specific value can be completed at a subsequent time using a concept recorded within an information model, entered into a data entry form, or sourced by some other means. When each slot in the template has been replaced with a specific value, the result should be a syntactically correct expression or expression constraint. SNOMED CT Templates templates can be used for a number of purposes, including to define reusable patterns for precoordination, postcoordination and terminology queries, and for binding SNOMED CT to information modelsauthoring and validating precoordinated concept definitions and postcoordinated expressions.
History
The SNOMED CT Template Syntax (v1.0) was first published in July 2017. In 2020, the syntax was updated (v1.1) to support boolean attribute values.
Purpose
The purpose of this document is to define and describe a consistent mechanism for SNOMED CT Templatestemplates, which can be used to convert any formal computable SNOMED CT language into a SNOMED CT Template template language. For example, by using the syntax provided in this document, SNOMED CT Compositional Grammar compositional grammar can be used as an Expression Template Language; expression template language, and the SNOMED CT Expression Constraint expression constraint Language can be used as an Expression Constraint Template Languageexpression constraint template language. This guide also provides examples and guidance to assist in the implementation processing of Templatestemplates.
Scope
This document presents the specification of a SNOMED CT Template Syntaxtemplate syntax, which can be used together with other formal SNOMED CT languages to develop SNOMED CT Templates. The SNOMED CT Template Syntax is part of a consistent set of computer processable language syntaxes designed to support a variety of use cases involving the use of SNOMED CT. Other computable SNOMED CT languages that are either complete or under development include:
- Compositional Grammar: designed to represent SNOMED CT expressions;
- Expression Constraint Language: designed to represent a bounded set of clinical meanings represented using SNOMED CT; and
- Query Language: designed to express computable queries over SNOMED CT content.
This document provides a specification, examples and general guidance to assist in the implementation representation and processing of SNOMED CT templates.
However, this document does not include a full description of how to implement a template parser or interpreter. It does not describe how to transform a template into other languages (such as OWL, SPARQL or SQL), or how to determine whether two templates are equivalent. It also does not describe how to implement a terminology server or an EHR which uses templates to constrain or query its content.
Audience
The target audiences of this document include:
- IHTSDO SNOMED International National Release Centres;
- SNOMED CT designers and developers, including designers and developers of EHR systems, information models, data entry interfaces, storage systems, decision support systems, retrieval and analysis systems, communication standards and terminology services;
- SNOMED CT terminology developers, including concept model designers, content authors, map developers, subset and constraint developers and release process managers.
It should be noted that this document contains both technical and non-technical content. In particular, the detailed logical model and formal syntax is specifically focussed at more technical readers. Less technical readers are encouraged to read the introductory material and examples.
Document Overview
This document defines the SNOMED CT Template Syntax template syntax and describes how and where it may be implemented. Chapter 2 begins by describing the some key use cases in which it is anticipated that SNOMED CT Templates will templates can be used. Chapter 3 then describes the requirements used to guide the definition of this syntax. In Chapter 4, the logical model of the Template Syntax template syntax is presented, while Chapter 5 defines the ABNF serialisation of the logical model. Chapter 6 then presents some examples of SNOMED CT Templates that conform to the Template Syntax, and Chapter 7 discusses some implementation considerations. Appendix A provides the complete syntax for a SNOMED CT Expression Template; and Appendix B provides the complete syntax for a SNOMED CT Expression Constraint Template.
Glossary
The following table contains the definition of terms used within this document. Please refer to the IHTSDO Glossary for additional SNOMED CT definitions.
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Term
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Definition
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Augmented Backus-Naur Form (ABNF)
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A language used to define the formal syntax of another language (as defined by Internet Standard 68, RFC 5234).
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The set of rules that govern the way in which SNOMED CT expressions are represented as a plain text string.
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A set of rules that determines the permitted sets of relationships between particular types of concepts.
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A structured combination of one or more concept identifiers used to express a clinical idea.
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Expression Constraint
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A computable rule that can be used to define a bounded set of clinical meanings.
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A representation of the rules that comprise the SNOMED CT Concept Model in a form that can be processed by computer software and applied to validate content.
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Representation of a clinical meaning using a combination of two or more concept identifiers is referred to as a postcoordinated expression.
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Representation of a clinical meaning using a single concept identifier is referred to as a precoordinated expression.
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A SNOMED CT file structure consisting of a set of references to SNOMED CT components.
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Substrate
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The SNOMED CT content over which an expression constraint is evaluated or a query is executed.
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page-breakexplains how to apply the SNOMED CT template syntax to other computable languages, and provides the syntax for the expression template language (ETL). In chapter 7, we explain the steps involved in processing an expression template to create a set of populated expressions. And finally, in chapter 8, we present some examples of SNOMED CT expression templates that conform to the syntaxes defined in Chapters 5 and 6.
Overview
Content Tools
Apps