Expression:
     QueryExpression | SelectExpression

SelectExpression:
     ( AsDictionaryExpression | AsSequenceExpression )

AsDictionaryExpression:
     DictionaryPropertyExpression , DictionaryPropertyExpression*

DictionaryPropertyExpression:
     PropertyNameExpression : SelectQueryExpression

PropertyNameExpression:
     StringLiteral | SignedIntLiteral | FloatLiteral

AsSequenceExpression:
     SequenceEntryExpression , SequenceEntryExpression*

SequenceEntryExpression:
     SelectQueryExpression

QueryExpression:
     (StreamSingleElementExpression | StreamMultiElementExpression) QueryStageExpression*

QueryStageExpression:
     DictionaryQueryExpression | SequenceQueryExpression | TypeMatchExpression

DictionaryQueryExpression:
     { (StringLiteral | SignedIntLiteral | FloatLiteral) }

SequenceQueryExpression:
     ( SequenceIndexExpression )

SequenceIndexExpression:
     UnsignedIntLiteral | AnyIndex

AnyIndex:
     ?

StreamSingleElementExpression:
     # ([0-9][0-9]*)?

StreamMultiElementExpression:
     $

TypeMatchExpression:
     RequireTypeExpression | TypeOrNullExpression

RequireTypeExpression:
     → TypeSpecification

TypeOrNullExpression:
     →? TypeSpecification

TypeSpecifications:
     number | int | uint | nint | float | string | dictionary | sequence | tag | tag$ [0-9][0-9]* | bool | datetime | timestamp | uri | enccbor | unknown | null