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The formal syntax for SNOMED CT expression templates (v1.1) is shown below. This syntax is derived by combining:
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; Compositional Grammar v2.4 with slot references (in blue)
expressionTemplate = ws [ (definitionStatus / tokenReplacementSlot) ws] subExpression ws
subExpression = focusConcept [ws ":" ws refinement]
definitionStatus = equivalentTo / subtypeOf
equivalentTo = "==="
subtypeOf = "<<<"
focusConcept = [templateInformationSlot ws] conceptReference *(ws "+" ws [templateInformationSlot ws] conceptReference)
conceptReference = conceptReplacementSlot / expressionReplacementSlot / ( conceptId [ws "|" ws term ws "|"] )
conceptId = sctId
term = nonwsNonPipe *( *SP nonwsNonPipe )
refinement = (attributeSet / attributeGroup) *( ws ["," ws] attributeGroup )
attributeGroup = [ templateInformationSlot ws ] "{" ws attributeSet ws "}"
attributeSet = attribute *(ws "," ws attribute)
attribute = [ templateInformationSlot ws ] attributeName ws "=" ws attributeValue
attributeName = conceptReference
attributeValue = expressionValue / QM stringValue QM / "#" numericValue / booleanValue / concreteValueReplacementSlot
expressionValue = conceptReference / "(" ws subExpression ws ")"
stringValue = 1*(anyNonEscapedChar / escapedChar)
numericValue = ["-"/"+"] (decimalValue / integerValue)
integerValue = digitNonZero *digit / zero
decimalValue = integerValue "." 1*digit
booleanValue = true / false
true = ("t"/"T") ("r"/"R") ("u"/"U") ("e"/"E")
false = ("f"/"F") ("a"/"A") ("l"/"L") ("s"/"S") ("e"/"E")
sctId = digitNonZero 5*17( digit )
ws = *( SP / HTAB / CR / LF ) ; optional white space
SP = %x20 ; space
HTAB = %x09 ; tab
CR = %x0D ; carriage return
LF = %x0A ; line feed
QM = %x22 ; quotation mark
BS = %x5C ; back slash
digit = %x30-39
zero = %x30
digitNonZero = %x31-39
nonwsNonPipe = %x21-7B / %x7D-7E / UTF8-2 / UTF8-3 / UTF8-4
anyNonEscapedChar = HTAB / CR / LF / %x20-21 / %x23-5B / %x5D-7E / UTF8-2 / UTF8-3 / UTF8-4
escapedChar = BS QM / BS BS
UTF8-2 = %xC2-DF UTF8-tail
UTF8-3 = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2( UTF8-tail ) / %xED %x80-9F UTF8-tail / %xEE-EF 2( UTF8-tail )
UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) / %xF1-F3 3( UTF8-tail ) / %xF4 %x80-8F 2( UTF8-tail )
UTF8-tail = %x80-BF
; Template Syntax v1.1
templateSlot = templateReplacementSlot / templateInformationSlot
templateReplacementSlot = conceptReplacementSlot / expressionReplacementSlot / tokenReplacementSlot / concreteValueReplacementSlot
conceptReplacementSlot = "[[" ws "+" ws conceptReplacement [slotName ws] "]]"
expressionReplacementSlot = "[[" ws "+" ws expressionReplacement [slotName ws] "]]"
tokenReplacementSlot = "[[" ws "+" ws tokenReplacement [slotName ws] "]]"
concreteValueReplacementSlot = "[[" ws "+" ws concreteValueReplacement [slotName ws] "]]"
conceptReplacement = "id" ws [ "(" ws slotExpressionConstraint ws ")" ws]
expressionReplacement = ["scg" ws] ["(" ws slotExpressionConstraint ws ")" ws]
tokenReplacement = "tok" ws [ "(" ws slotTokenSet ws ")" ws]
concreteValueReplacement = stringReplacement / integerReplacement / decimalReplacement / booleanReplacement
stringReplacement = "str" ws [ "(" ws slotStringSet ws ")" ws]
integerReplacement = "int" ws [ "(" ws slotIntegerSet ws ")" ws]
decimalReplacement = "dec" ws [ "(" ws slotDecimalSet ws ")" ws]
booleanReplacement = "bool" ws [ "(" ws slotBooleanSet ws ")" ws]
slotTokenSet = slotToken *(mws slotToken)
slotStringSet = slotString slotStringValue *(mws slotStringslotStringValue)
slotStringValue = QM stringValue QM
slotIntegerSet = ( slotIntegerValue / slotIntegerRange) *(mws (slotIntegerValue / slotIntegerRange))
slotDecimalSet = ( slotDecimalValue / slotDecimalRange) *(mws (slotDecimalValue / slotDecimalRange))
slotBooleanSet = slotBooleanValue *(mws slotBooleanValue)
slotBooleanValue = booleanValue
slotIntegerRange = ( slotIntegerMinimum to [ slotIntegerMaximum ] ) / ( to slotIntegerMaximum )
slotIntegerMinimum = [ exclusiveMinimum ] slotIntegerValue
slotIntegerMaximum = [ exclusiveMaximum ] slotIntegerValue
slotIntegerValue = "#" digitNonZero *digit " ["-"/"#+" zero] integerValue
slotDecimalRange = ( slotDecimalMinimum to [ slotDecimalMaximum ] ) / ( to slotDecimalMaximum )
slotDecimalMinimum = [ exclusiveMinimum ] slotDecimalValue
slotDecimalMaximum = [ exclusiveMaximum ] slotDecimalValue
slotDecimalValue = "#" integerValue "." 1*digit ["-"/"+"] decimalValue
exclusiveMinimum = ">"
exclusiveMaximum = "<"
slotBooleanValue = true / false
; true = ("t"/"T") ("r"/"R") ("u"/"U") ("e"/"E")
; false = ("f"/"F") ("a"/"A") ("l"/"L") ("s"/"S") ("e"/"E")
slotName = "@" (nonQuoteStringValue / slotStringslotStringValue)
slotToken = definitionStatus / memberOf / constraintOperator / conjunction / disjunction / exclusion / reverseFlag / expressionComparisonOperator / numericComparisonOperator / stringComparisonOperator / booleanComparisonOperator
slotString = QM slotStringValue QM
nonQuoteStringValue = *(%x21 / %x23-26 / %x2A-3F / %x41-5A / %x5C / %x5E-7E) ; string with no ws, quotes, at, square brackets or round brackets
templateInformationSlot = "[[" ws slotInformation ws "]]"
slotInformation = [cardinality ws] [slotName ws]
; Expression Constraint Language v1.4 - Note that some rules are commented out because they are repeated in the Compositional Grammar rules above.
slotExpressionConstraint = ws ( slotRefinedExpressionConstraint / slotCompoundExpressionConstraint / slotDottedExpressionConstraint / slotSubExpressionConstraint ) ws
slotRefinedExpressionConstraint = slotSubExpressionConstraint ws ":" ws slotEclRefinement
slotCompoundExpressionConstraint = slotConjunctionExpressionConstraint / slotDisjunctionExpressionConstraint / slotExclusionExpressionConstraint
slotConjunctionExpressionConstraint = slotSubExpressionConstraint 1*(ws conjunction ws slotSubExpressionConstraint)
slotDisjunctionExpressionConstraint = slotSubExpressionConstraint 1*(ws disjunction ws slotSubExpressionConstraint)
slotExclusionExpressionConstraint = slotSubExpressionConstraint ws exclusion ws slotSubExpressionConstraint
slotDottedExpressionConstraint = slotSubExpressionConstraint 1*(ws slotDottedExpressionAttribute)
slotDottedExpressionAttribute = dot ws slotEclAttributeName
slotSubExpressionConstraint = [constraintOperator ws] [memberOf ws] (slotEclFocusConcept / "(" ws slotExpressionConstraint ws ")")
slotEclFocusConcept = slotEclConceptReference / wildCard
dot = "."
memberOf = "^"
slotEclConceptReference = conceptId [ws "|" ws term ws "|"]
; conceptId = sctId
; term = 1*nonwsNonPipe *( 1*SP 1*nonwsNonPipe )
wildcard = "*"
constraintOperator = childOf / descendantOrSelfOf / descendantOf / parentOf / ancestorOrSelfOf / ancestorOf
descendantOf = "<"
descendantOrSelfOf = "<<"
childOf = "<!"
ancestorOf = ">"
ancestorOrSelfOf = ">>"
parentOf = ">!"
conjunction = (("a"/"A") ("n"/"N") ("d"/"D") mws) / ","
disjunction = ("o"/"O") ("r"/"R") mws
exclusion = ("m"/"M") ("i"/"I") ("n"/"N") ("u"/"U") ("s"/"S") mws
slotEclRefinement = slotSubRefinement ws [slotConjunctionRefinementSet / slotDisjunctionRefinementSet]
slotConjunctionRefinementSet = 1*(ws conjunction ws slotSubRefinement)
slotDisjunctionRefinementSet = 1*(ws disjunction ws slotSubRefinement)
slotSubRefinement = slotEclAttributeSet / slotEclAttributeGroup / "(" ws slotEclRefinement ws ")"
slotEclAttributeSet = slotSubAttributeSet ws [slotConjunctionAttributeSet / slotDisjunctionAttributeSet]
slotConjunctionAttributeSet = 1*(ws conjunction ws slotSubAttributeSet)
slotDisjunctionAttributeSet = 1*(ws disjunction ws slotSubAttributeSet)
slotSubAttributeSet = slotEclAttribute / "(" ws slotEclAttributeSet ws ")"
slotEclAttributeGroup = ["[" cardinality "]" ws] "{" ws slotEclAttributeSet ws "}"
slotEclAttribute = ["[" cardinality "]" ws] [reverseFlag ws] slotEclAttributeName ws (expressionComparisonOperator ws slotSubExpressionConstraint / numericComparisonOperator ws slotNumericValue / stringComparisonOperator ws slotStringValue / booleanComparisonOperator ws booleanValue)
cardinality = minValue to maxValue
minValue = nonNegativeIntegerValue
to = ".."
maxValue = nonNegativeIntegerValue / many
many = "*"
reverseFlag = "R"
slotEclAttributeName = slotSubExpressionConstraint
expressionComparisonOperator = "=" / "!="
numericComparisonOperator = "=" / "!=" / "<=" / "<" / ">=" / ">"
stringComparisonOperator = "=" / "!="
booleanComparisonOperator = "=" / "!="
slotNumericValue = "#" numericValue
; stringValue = 1*(anyNonEscapedChar / escapedChar)
; numericValue = ["-"/"+"] (slotDecimalValue / slotIntegerValue)slotStringValue = QM 1*(anyNonEscapedChar / escapedChar) QMdecimalValue / integerValue)
; integerValue = digitNonZero *digit / zero
; decimalValue = integerValue "." 1*digit
; booleanValue = true / false
; true = ("t"/"T") ("r"/"R") ("u"/"U") ("e"/"E")
; false = ("f"/"F") ("a"/"A") ("l"/"L") ("s"/"S") ("e"/"E")
nonNegativeIntegerValue = (digitNonZero *digit ) / zero
; sctId = digitNonZero 5*17( digit )
; ws = *( SP / HTAB / CR / LF / comment ) ; optional white space
mws = 1*( SP / HTAB / CR / LF / comment ) ; mandatory white space
comment = "/*" *(nonStarChar / starWithNonFSlash) "*/"
nonStarChar = SP / HTAB / CR / LF / %x21-29 / %x2B-7E /UTF8-2 / UTF8-3 / UTF8-4
starWithNonFSlash = %x2A nonFSlash
nonFSlash = SP / HTAB / CR / LF / %x21-2E / %x30-7E /UTF8-2 / UTF8-3 / UTF8-4
; SP = %x20 ; space
; HTAB = %x09 ; tab
; CR = %x0D ; carriage return
; LF = %x0A ; line feed
; QM = %x22 ; quotation mark
; BS = %x5C ; back slash
; digit = %x30-39
; zero = %x30
; digitNonZero = %x31-39
; nonwsNonPipe = %x21-7B / %x7D-7E / UTF8-2 / UTF8-3 / UTF8-4
; anyNonEscapedChar = SP / HTAB / CR / LF / %x20-21 / %x23-5B / %x5D-7E / UTF8-2 / UTF8-3 / UTF8-4
; escapedChar = BS QM / BS BS
; UTF8-2 = %xC2-DF UTF8-tail
; UTF8-3 = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2( UTF8-tail ) / %xED %x80-9F UTF8-tail / %xEE-EF 2( UTF8-tail )
; UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) / %xF1-F3 3( UTF8-tail ) / %xF4 %x80-8F 2( UTF8-tail )
; UTF8-tail = %x80-BF
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