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.

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1. Introduction

2. Use Cases

3. Requirements

4. Logical Model

5. Syntax Specification

6. Examples

7. Implementation Considerations

Appendix A – Examples Of Valid Expressions

Appendix B – Examples Of Invalid Expressions

Appendix C - Dialect Aliases

Appendix D - ECL Quick Reference

Appendix E - Reference Set Fields


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