Clinical Quality Language

Grammar Reference

Interactive railroad diagrams for all 113 production rules of the CQL 1.5 grammar. Click any rule name on a diagram to navigate directly to its definition.

library root rule

The root rule of every CQL file. A library may optionally begin with a library declaration, followed by zero or more definitions (using, include, codesystem, valueset, code, concept, parameter), then zero or more statements (expressions, contexts, functions), and finally the end-of-file marker.

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v1.5 Mixed Normative / Trial-Use 113 rules · 11 groups
Top Level 3

The root production rules that define the overall structure of a CQL library.

definition library statement
Definitions 18

Library-level declarations that introduce named artifacts such as code systems, value sets, codes, concepts, parameters, using imports, and include imports.

accessModifier codeDefinition codeId codeIdentifier codesystemDefinition codesystemId codesystemIdentifier codesystems conceptDefinition includeDefinition libraryDefinition libraryIdentifier localIdentifier parameterDefinition usingDefinition valuesetDefinition valuesetId versionSpecifier
Type Specifiers 8

Grammar rules that describe CQL types, including named types, lists, intervals, tuples, and choice types.

choiceTypeSpecifier intervalTypeSpecifier listTypeSpecifier modelIdentifier namedTypeSpecifier tupleElementDefinition tupleTypeSpecifier typeSpecifier
Statements 6

Executable declarations within a CQL library: expression definitions, context switches, and function definitions.

contextDefinition expressionDefinition fluentModifier functionDefinition functionBody operandDefinition
Expressions 18

The core expression grammar covering all value-producing constructs including queries, retrieves, timing operators, and arithmetic.

alias aliasedQuerySource caseExpressionItem codeComparator codePath contextIdentifier dateTimePrecision dateTimeComponent expression expressionTerm pluralDateTimePrecision query queryInclusionClause querySource retrieve terminology withoutClause withClause
Query Clauses 10

The individual clauses of a CQL query: source, let, with/without, where, return, aggregate, and sort.

aggregateClause letClause letClauseItem returnClause sortClause sortDirection sortByItem sourceClause startingClause whereClause
Terms & Literals 8

Fundamental expression units: literals, identifiers, invocations, and selector expressions.

externalConstant function invocation literal qualifiedFunction qualifiedInvocation ratio term
Selectors 9

Inline constructor expressions for intervals, tuples, instances, lists, codes, and concepts.

codeSelector conceptSelector displayClause instanceElementSelector instanceSelector intervalSelector listSelector tupleSelector tupleElementSelector
Interval Operators 7

Temporal and interval relationship operator phrases used in timing expressions.

dateTimePrecisionSpecifier exclusiveRelativeQualifier intervalOperatorPhrase offsetRelativeQualifier quantityOffset relativeQualifier temporalRelationship
Identifiers 16

Identifier and name resolution grammar including qualified identifiers and keyword identifiers.

functionIdentifier identifierOrFunctionIdentifier identifier keyword keywordIdentifier obsoleteIdentifier qualifiedIdentifier qualifiedIdentifierExpression qualifier qualifierExpression referentialIdentifier referentialOrTypeNameIdentifier reservedWord simpleLiteral simplePath typeNameIdentifier
Lexer Tokens 10

Lexer token definitions describing the low-level character patterns for identifiers, literals, and other terminal symbols.

DATE DATETIME DELIMITEDIDENTIFIER EOF IDENTIFIER LONGNUMBER NUMBER QUOTEDIDENTIFIER STRING TIME

Grammar source: HL7 Clinical Quality Language Specification 1.5 (ANTLR4). Non-terminals link to their respective rule pages.