The Expression Constraint Language is a formal syntax for representing SNOMED CT expression constraints. Expression constraints are computable rules used to define a bounded sets of clinical meanings represented by either precoordinated or postcoordinated expressions. Expression constraints can be used to restrict the valid values for a data element in an EHR, as the intensional definition of a concept-based reference set, as a machine processable query that identifies a set of matching expressions, or as a constraint that restricts the range of an attribute defined in the SNOMED CT concept model.
This document defines and describes the current version of the Expression Constraint Language - ECL v2.2.
Web browsable version: http://snomed.org/ecl
SNOMED CT Document Library: http://snomed.org/doc
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Contents
1. Introduction
2. Use Cases
- 2.1 Terminology Binding
- 2.2 Intensional Reference Set Definitions
- 2.3 SNOMED CT Content Queries
- 2.4 SNOMED CT Concept Model
3. Requirements
- 3.1 General SNOMED CT Language Requirements
- 3.2 Expression Constraint and Query Requirements
- 3.3 Concept Model Requirements
4. Logical Model
5. Syntax Specification
- 5.1 Brief Syntax (Normative)
- 5.2 Long Syntax (Informative)
- 5.3 Informative Comments
- 5.4 Order of Operation
- 5.5 Character Collation for Term Filters
6. Examples
- 6.1 Simple Expression Constraints
- 6.2 Refinements
- 6.3 Cardinality
- 6.4 Conjunction and Disjunction
- 6.5 Exclusion and Not Equals
- 6.6 Constraint Comments
- 6.7 Nested Expression Constraints
- 6.8 Description Filters
- 6.9 Concept Filters
- 6.10 Member Filters
- 6.11 History Supplements
- 6.12 Top and Bottom
7. Implementation Considerations
Appendix A – Examples Of Valid Expressions
- A.1 Simple Expression Constraints - Valid Expressions
- A.2 Refinements - Valid Expressions
- A.3 Cardinality - Valid Expressions
- A.4 Conjunction and Disjunction - Valid Expressions
- A.5 Exclusion and Not Equals - Valid Expressions
- A.6 Nested Expression Constraints - Valid Expressions
Appendix B – Examples Of Invalid Expressions
- B.1 Simple Expression Constraints - Invalid Expressions
- B.2 Refinements - Invalid Expressions
- B.3 Cardinality - Invalid Expressions
- B.4 Conjunction and Disjunction - Invalid Expressions
- B.5 Exclusion and Not Equals - Invalid Expressions
- B.6 Nested Expression Constraints - Invalid Expressions
Appendix C - Dialect Aliases
Appendix D - ECL Quick Reference
Appendix E - Reference Set Fields
References
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