define "Initial Population":
  AgeInYearsAt(date from 
    end of "Measurement Period"
  ) in Interval[18, 75]
    and exists ( "Qualifying Encounters" )
    and exists ( ( ( [ConditionEncounterDiagnosis: "Diabetes"] ).verified ( ) ) DiabetesDx
        where DiabetesDx.prevalenceInterval ( ) overlaps day of "Measurement Period"
    )

define "Initial Population":
  AgeInYearsAt(date from 
    end of "Measurement Period"
  ) in Interval[18, 75]
    and exists ( "Qualifying Encounters" )
    and exists ( ( ( [ConditionEncounterDiagnosis: "Diabetes"] ).verified ( ) ) DiabetesDx
        where DiabetesDx.prevalenceInterval ( ) overlaps day of "Measurement Period"
    )

define "Denominator":
  "Initial Population"

define "Denominator Exclusions":
  Hospice."Has Hospice Services"
    or AIFrailLTCF."Is Age 66 or Older with Advanced Illness and Frailty"
    or AIFrailLTCF."Is Age 66 or Older Living Long Term in a Nursing Home"
    or PalliativeCare."Has Palliative Care in the Measurement Period"
    or "Bilateral Absence of Eyes"

define "Numerator":
  ( "Diabetic Retinopathy Overlapping Measurement Period"
      and ( "Retinal Exam in Measurement Period" )
  )
    or ( not ( "Diabetic Retinopathy Overlapping Measurement Period" )
        and ( "Retinal Exam in Measurement Period or Year Prior" )
    )
    or "Autonomous Eye Exam in Measurement Period"
    or "Retinal Exam Finding with Retinopathy Severity Level in Measurement Period"
    or "Retinal Exam Finding with No Retinopathy Severity Level in Year Prior"

define "Has Hospice Services":
  exists ((([Encounter: "Encounter Inpatient"]).isEncounterPerformed()) InpatientEncounter
      where (InpatientEncounter.hospitalization.dischargeDisposition ~ "Discharge to home for hospice care (procedure)"
          or InpatientEncounter.hospitalization.dischargeDisposition ~ "Discharge to healthcare facility for hospice care (procedure)"
      )
        and InpatientEncounter.period ends during day of "Measurement Period"
  )
    or exists ((([Encounter: "Hospice Encounter"]).isEncounterPerformed()) HospiceEncounter
        where HospiceEncounter.period overlaps day of "Measurement Period"
    )
    or exists ((([ObservationScreeningAssessment: "Hospice care [Minimum Data Set]"]).isAssessmentPerformed()) HospiceAssessment
        where HospiceAssessment.value ~ "Yes (qualifier value)"
          and HospiceAssessment.effective.toInterval() overlaps day of "Measurement Period"
    )
    or exists ((([ServiceRequest: "Hospice Care Ambulatory"]).isInterventionOrder()) HospiceOrder
        where HospiceOrder.authoredOn during day of "Measurement Period"
    )
    or exists ((([Procedure: "Hospice Care Ambulatory"]).isInterventionPerformed()) HospicePerformed
        where HospicePerformed.performed.toInterval() overlaps day of "Measurement Period"
    )
    or exists ((([ConditionProblemsHealthConcerns: "Hospice Diagnosis"]
        union [ConditionEncounterDiagnosis: "Hospice Diagnosis"]).verified()) HospiceCareDiagnosis
        where HospiceCareDiagnosis.prevalenceInterval() overlaps day of "Measurement Period"
    )

define "Has Criteria Indicating Frailty":
  exists ( (([DeviceRequest: "Frailty Device"]).isDeviceOrderPersonalUseDevices()) FrailtyDeviceOrder
      where FrailtyDeviceOrder.authoredOn.toInterval() during day of "Measurement Period"
  )
    or exists ( (([ObservationScreeningAssessment: "Medical equipment used"]).isAssessmentPerformed()) EquipmentUsed
        where EquipmentUsed.value as Concept in "Frailty Device" 
        and EquipmentUsed.effective.toInterval() ends during day of "Measurement Period"
    )
    or exists ( (([ConditionProblemsHealthConcerns: "Frailty Diagnosis"]
    union [ConditionEncounterDiagnosis: "Frailty Diagnosis"]).verified()) FrailtyDiagnosis
        where FrailtyDiagnosis.prevalenceInterval() overlaps day of "Measurement Period"
    )
    or exists ( (([Encounter: "Frailty Encounter"]).isEncounterPerformed()) FrailtyEncounter
        where FrailtyEncounter.period overlaps day of "Measurement Period"
    )
    or exists ( (([SimpleObservation: "Frailty Symptom"]).isSymptom()) FrailtySymptom
        where FrailtySymptom.effective.toInterval() overlaps day of "Measurement Period"
    )

define "Has Advanced Illness in Year Before or During Measurement Period":
exists ((([ConditionProblemsHealthConcerns: "Advanced Illness"]
union [ConditionEncounterDiagnosis: "Advanced Illness"]).verified()) AdvancedIllnessDiagnosis
where AdvancedIllnessDiagnosis.prevalenceInterval() starts during day of Interval[start of "Measurement Period" - 1 year, end of "Measurement Period"])

define "Has Dementia Medications in Year Before or During Measurement Period":
  exists (( ([MedicationRequest: "Dementia Medications"]).isMedicationActive()) DementiaMedication
      where DementiaMedication.medicationRequestPeriod() overlaps day of Interval[start of "Measurement Period" - 1 year, 
        end of "Measurement Period"]
  )

define "Is Age 66 or Older with Advanced Illness and Frailty":
   AgeInYearsAt(date from end of "Measurement Period")>= 66
    and "Has Criteria Indicating Frailty"
    and ( "Has Advanced Illness in Year Before or During Measurement Period"
        or "Has Dementia Medications in Year Before or During Measurement Period"
    )

define "Is Age 66 or Older Living Long Term in a Nursing Home":
  AgeInYearsAt(date from 
     end of "Measurement Period"
  )>= 66
    and ( ( Last( (([ObservationScreeningAssessment: "Housing status"]).isAssessmentPerformed()) HousingStatus    
          where HousingStatus.effective.toInterval() ends on or before 
          day of end of "Measurement Period"
          sort by 
          end of effective.toInterval() asc
      )) LastHousingStatus
        where LastHousingStatus.value ~ "Lives in nursing home (finding)"
    ) is not null

define "Has Palliative Care in the Measurement Period":
  exists ((([ObservationScreeningAssessment: "Functional Assessment of Chronic Illness Therapy - Palliative Care Questionnaire (FACIT-Pal)"]).isAssessmentPerformed()) PalliativeAssessment
      where PalliativeAssessment.effective.toInterval() overlaps day of "Measurement Period"
  )
    or exists ((([ConditionProblemsHealthConcerns: "Palliative Care Diagnosis"]
    union [ConditionEncounterDiagnosis: "Palliative Care Diagnosis"]).verified()) PalliativeDiagnosis
        where PalliativeDiagnosis.prevalenceInterval() overlaps day of "Measurement Period"
    )
    or exists ((([Encounter: "Palliative Care Encounter"]).isEncounterPerformed()) PalliativeEncounter
        where PalliativeEncounter.period overlaps day of "Measurement Period"
    )
    or exists ((([Procedure: "Palliative Care Intervention"]).isInterventionPerformed()) PalliativeIntervention
        where PalliativeIntervention.performed.toInterval() overlaps day of "Measurement Period"
    )

define "SDE Sex":
  case
    when Patient.sex = '248153007' then "Male (finding)"
    when Patient.sex = '248152002' then "Female (finding)"
    else null
  end

define "SDE Payer":
  [Coverage: type in "Payer Type"] Payer
    return {
      code: Payer.type,
      period: Payer.period
    }

define "SDE Ethnicity":
  Patient.ethnicity E
    return Tuple {
      codes: { E.ombCategory } union E.detailed,
      display: E.text
    }

define "SDE Race":
  Patient.race R
    return Tuple {
      codes: R.ombCategory union R.detailed,
      display: R.text
    }

define "SDE Sex":
  SDE."SDE Sex"

define "Diabetic Retinopathy Overlapping Measurement Period":
  exists ( ( [ConditionProblemsHealthConcerns: "Diabetic Retinopathy"]
      union [ConditionEncounterDiagnosis: "Diabetic Retinopathy"]
  ).verified ( ) ) Retinopathy
    where Retinopathy.prevalenceInterval ( ) overlaps day of "Measurement Period"

define "Retinal Exam in Measurement Period":
  exists ( ( [ObservationClinicalResult: "Retinal or Dilated Eye Exam"] ).isPhysicalExamPerformed ( ) ) RetinalExam
    where RetinalExam.effective.toInterval ( ) during day of "Measurement Period"

define "Retinal Exam in Measurement Period or Year Prior":
  exists ( ( [ObservationClinicalResult: "Retinal or Dilated Eye Exam"] ).isPhysicalExamPerformed ( ) ) RetinalExam
    where RetinalExam.effective.toInterval ( ) during day of Interval[start of "Measurement Period" - 1 year, end of "Measurement Period"]

define "Autonomous Eye Exam in Measurement Period":
  exists ( ( [ObservationClinicalResult: "Eye Diabetic retinopathy screening Autonomous artificial intelligence"] ).isPhysicalExamPerformed ( ) ) AutonomousEyeExam
    where AutonomousEyeExam.value as Concept in "Autonomous Eye Exam Result or Finding"
      and AutonomousEyeExam.effective.toInterval ( ) during day of "Measurement Period"

define "Has Left Eye Retinopathy":
  exists ( ( [ObservationClinicalResult: "Left eye Diabetic retinopathy severity level by Ophthalmoscopy"] ).isPhysicalExamPerformed ( ) ) LeftEyeRetinopathy
    where LeftEyeRetinopathy.value as Concept in "Diabetic Retinopathy Severity Level"
      and LeftEyeRetinopathy.effective.toInterval ( ) during day of "Measurement Period"

define "Has Right Eye Retinopathy":
  exists ( ( [ObservationClinicalResult: "Right eye Diabetic retinopathy severity level by Ophthalmoscopy"] ).isPhysicalExamPerformed ( ) ) RightEyeRetinopathy
    where RightEyeRetinopathy.value as Concept in "Diabetic Retinopathy Severity Level"
      and RightEyeRetinopathy.effective.toInterval ( ) during day of "Measurement Period"

define "Has Right Eye No Retinopathy in Year Prior":
  exists ( ( [ObservationClinicalResult: "Right eye Diabetic retinopathy severity level by Ophthalmoscopy"] ).isPhysicalExamPerformed ( ) ) RightEyeNoRetinopathy
    where RightEyeNoRetinopathy.value ~ "No apparent retinopathy"
      and RightEyeNoRetinopathy.effective.toInterval ( ) during day of Interval[start of "Measurement Period" - 1 year, end of "Measurement Period" - 1 year]

define "Has Left Eye No Retinopathy in Year Prior":
  exists ( ( [ObservationClinicalResult: "Left eye Diabetic retinopathy severity level by Ophthalmoscopy"] ).isPhysicalExamPerformed ( ) ) LeftEyeNoRetinopathy
    where LeftEyeNoRetinopathy.value ~ "No apparent retinopathy"
      and LeftEyeNoRetinopathy.effective.toInterval ( ) during day of Interval[start of "Measurement Period" - 1 year, end of "Measurement Period" - 1 year]

define "Retinal Exam Finding with Retinopathy Severity Level in Measurement Period":
  ( "Has Left Eye Retinopathy"
      and "Has Right Eye Retinopathy"
  )
    or ( "Has Left Eye Retinopathy"
        and "Has Right Eye No Retinopathy in Year Prior"
    )
    or ( "Has Right Eye Retinopathy"
        and "Has Left Eye No Retinopathy in Year Prior"
    )

define "Retinal Exam Finding with No Retinopathy Severity Level in Year Prior":
  ( "Has Left Eye No Retinopathy in Year Prior"
      and "Has Right Eye No Retinopathy in Year Prior"
  )

define "Numerator":
  ( "Diabetic Retinopathy Overlapping Measurement Period"
      and ( "Retinal Exam in Measurement Period" )
  )
    or ( not ( "Diabetic Retinopathy Overlapping Measurement Period" )
        and ( "Retinal Exam in Measurement Period or Year Prior" )
    )
    or "Autonomous Eye Exam in Measurement Period"
    or "Retinal Exam Finding with Retinopathy Severity Level in Measurement Period"
    or "Retinal Exam Finding with No Retinopathy Severity Level in Year Prior"

define "Qualifying Encounters":
  ( ( [Encounter: "Office Visit"]
      union [Encounter: "Annual Wellness Visit"]
      union [Encounter: "Preventive Care Services Established Office Visit, 18 and Up"]
      union [Encounter: "Preventive Care Services Initial Office Visit, 18 and Up"]
      union [Encounter: "Home Healthcare Services"]
      union [Encounter: "Ophthalmological Services"]
      union [Encounter: "Telephone Visits"]
  ).isEncounterPerformed ( ) ) ValidEncounters
    where ValidEncounters.period during day of "Measurement Period"

define "Initial Population":
  AgeInYearsAt(date from 
    end of "Measurement Period"
  ) in Interval[18, 75]
    and exists ( "Qualifying Encounters" )
    and exists ( ( ( [ConditionEncounterDiagnosis: "Diabetes"] ).verified ( ) ) DiabetesDx
        where DiabetesDx.prevalenceInterval ( ) overlaps day of "Measurement Period"
    )

define "Denominator":
  "Initial Population"

define "SDE Payer":
  SDE."SDE Payer"

define "Initial Population":
  AgeInYearsAt(date from 
    end of "Measurement Period"
  ) in Interval[18, 75]
    and exists ( "Qualifying Encounters" )
    and exists ( ( ( [ConditionEncounterDiagnosis: "Diabetes"] ).verified ( ) ) DiabetesDx
        where DiabetesDx.prevalenceInterval ( ) overlaps day of "Measurement Period"
    )

define "SDE Ethnicity":
  SDE."SDE Ethnicity"

define "Bilateral Absence of Eyes":
  exists ( ( [ConditionProblemsHealthConcerns: "Anophthalmos of bilateral eyes (disorder)"]
      union [ConditionEncounterDiagnosis: "Anophthalmos of bilateral eyes (disorder)"]
  ).verified ( ) ) BilateralAbsenceEyes
    where BilateralAbsenceEyes.prevalenceInterval ( ) starts on or before day of end of "Measurement Period"

define "Denominator Exclusions":
  Hospice."Has Hospice Services"
    or AIFrailLTCF."Is Age 66 or Older with Advanced Illness and Frailty"
    or AIFrailLTCF."Is Age 66 or Older Living Long Term in a Nursing Home"
    or PalliativeCare."Has Palliative Care in the Measurement Period"
    or "Bilateral Absence of Eyes"

define "SDE Race":
  SDE."SDE Race"

define function ToString(value uri): value.value

/*
@description: Converts the given FHIR [CodeableConcept](https://hl7.org/fhir/datatypes.html#CodeableConcept) value to a CQL Concept.
*/
define function ToConcept(concept FHIR.CodeableConcept):
    if concept is null then
        null
    else
        System.Concept {
            codes: concept.coding C return ToCode(C),
            display: concept.text.value
        }

/*
@description: Converts the given FHIR [Coding](https://hl7.org/fhir/datatypes.html#Coding) value to a CQL Code.
*/
define function ToCode(coding FHIR.Coding):
    if coding is null then
        null
    else
        System.Code {
          code: coding.code.value,
          system: coding.system.value,
          version: coding.version.value,
          display: coding.display.value
        }

/*
@description: Converts the given [Period](https://hl7.org/fhir/datatypes.html#Period)
value to a CQL DateTime Interval
@comment: If the start value of the given period is unspecified, the starting
boundary of the resulting interval will be open (meaning the start of the interval
is unknown, as opposed to interpreted as the beginning of time).
*/
define function ToInterval(period FHIR.Period):
    if period is null then
        null
    else
        if period."start" is null then
            Interval(period."start".value, period."end".value]
        else
            Interval[period."start".value, period."end".value]

/*
@description: Normalizes a value that is a choice of timing-valued types to an equivalent interval
@comment: Normalizes a choice type of DateTime, Quanitty, Interval<DateTime>, or Interval<Quantity> types
to an equivalent interval. This selection of choice types is a superset of the majority of choice types that are used as possible
representations for timing-valued elements in QICore, allowing this function to be used across any resource.
The input can be provided as a DateTime, Quantity, Interval<DateTime> or Interval<Quantity>.
The intent of this function is to provide a clear and concise mechanism to treat single
elements that have multiple possible representations as intervals so that logic doesn't have to account
for the variability. More complex calculations (such as medication request period or dispense period
calculation) need specific guidance and consideration. That guidance may make use of this function, but
the focus of this function is on single element calculations where the semantics are unambiguous.
If the input is a DateTime, the result a DateTime Interval beginning and ending on that DateTime.
If the input is a Quantity, the quantity is expected to be a calendar-duration interpreted as an Age,
and the result is a DateTime Interval beginning on the Date the patient turned that age and ending immediately before one year later.
If the input is a DateTime Interval, the result is the input.
If the input is a Quantity Interval, the quantities are expected to be calendar-durations interpreted as an Age, and the result
is a DateTime Interval beginning on the date the patient turned the age given as the start of the quantity interval, and ending
immediately before one year later than the date the patient turned the age given as the end of the quantity interval.
If the input is a Timing, an error will be thrown indicating that Timing calculations are not implemented. Any other input will reslt in a null DateTime Interval
*/
define fluent function toInterval(choice Choice<DateTime, Quantity, Interval<DateTime>, Interval<Quantity>, Timing>):
  case
	  when choice is DateTime then
    	Interval[choice as DateTime, choice as DateTime]
		when choice is Interval<DateTime> then
  		choice as Interval<DateTime>
		when choice is Quantity then
		  Interval[Patient.birthDate + (choice as Quantity),
			  Patient.birthDate + (choice as Quantity) + 1 year)
		when choice is Interval<Quantity> then
		  Interval[Patient.birthDate + (choice.low as Quantity),
			  Patient.birthDate + (choice.high as Quantity) + 1 year)
		when choice is Timing then
      Message(null, true, 'NOT_IMPLEMENTED', 'Error', 'Calculation of an interval from a Timing value is not supported') as Interval<DateTime>
		else
			null as Interval<DateTime>
	end

//This library contains functions used to constrain FHIR resource elements for measures authored by NCQA, based on QICore 6.0.0 resources including IG and authoring patterns. The functions may appear similar to some QICoreCommon functions but differ in that they have constraints that are relevant for measures authored by NCQA.

//Condition
//Returns conditions in the given list that either have no verification status or have a verification status of confirmed, unconfirmed, provisional, or differential
define fluent function verified(conditions List<Choice<ConditionProblemsHealthConcerns, ConditionEncounterDiagnosis>>):
  conditions C
    where C.verificationStatus is not null implies
      (C.verificationStatus ~ "confirmed"
        or C.verificationStatus ~ "unconfirmed"
        or C.verificationStatus ~ "provisional"
        or C.verificationStatus ~ "differential"
      )

//Physical Exam, Performed
define fluent function isPhysicalExamPerformed(Obs List<ObservationClinicalResult>):
  Obs O
    where O.status in { 'final', 'amended', 'corrected' }
      and exists ( O.category ObservationCategory
          where ( ObservationCategory ) ~ "exam"
      )

//Encounter, Performed
//General usage unless required otherwise by measure intent (e.g., follow-up encounters)
define fluent function isEncounterPerformed(Enc List<Encounter>):
  Enc E
    where E.status = 'finished'

//Assessment, Performed
define fluent function isAssessmentPerformed(Obs List<ObservationScreeningAssessment>):
  Obs O
    where O.status in { 'final', 'amended', 'corrected' }

//Intervention, Order
define fluent function isInterventionOrder(ServiceRequest List<ServiceRequest>):
  ServiceRequest S
    where S.status in { 'active', 'completed' }
      and S.intent in {'order', 'original-order', 'reflex-order', 'filler-order', 'instance-order'}

//Intervention, Performed
define fluent function isInterventionPerformed(Proc List<Procedure>):
  Proc P
    where P.status ~ 'completed'

//Device, Order - Personal Use Devices
define fluent function isDeviceOrderPersonalUseDevices(DeviceRequest List<DeviceRequest>):
  DeviceRequest D
    where D.status in { 'active', 'completed' }
      and D.intent in {'order', 'original-order', 'reflex-order', 'filler-order', 'instance-order'}

//Symptom
define fluent function isSymptom(Obs List<SimpleObservation>):
  Obs O
    where O.status in { 'preliminary', 'final', 'amended', 'corrected' }

//Medication, Active
define fluent function isMedicationActive(MedicationRequest List<MedicationRequest>):
  MedicationRequest M
    where M.status = 'active'
      and M.intent in {'order', 'original-order', 'reflex-order', 'filler-order', 'instance-order'}

define fluent function medicationRequestPeriod(Request "MedicationRequest"):
  Request R
    let
      dosage: singleton from R.dosageInstruction,
      doseAndRate: singleton from dosage.doseAndRate,
      timing: dosage.timing,
      frequency: Coalesce(timing.repeat.frequencyMax, timing.repeat.frequency),
      period: Quantity(timing.repeat.period, timing.repeat.periodUnit),
      doseRange: doseAndRate.dose,
      doseQuantity: doseAndRate.dose,
      dose: Coalesce(end of doseRange, doseQuantity),
      dosesPerDay: Coalesce(ToDaily(frequency, period), Count(timing.repeat.timeOfDay), 1.0),
      boundsPeriod: timing.repeat.bounds as Interval<DateTime>,
      daysSupply: (convert R.dispenseRequest.expectedSupplyDuration to days).value,
      quantity: R.dispenseRequest.quantity,
      refills: Coalesce(R.dispenseRequest.numberOfRepeatsAllowed, 0),
      startDate:
        Coalesce(
          date from start of boundsPeriod,
          date from R.authoredOn,
          date from start of R.dispenseRequest.validityPeriod
        ),
      totalDaysSupplied: Coalesce(daysSupply, quantity.value / (dose.value * dosesPerDay)) * (1 + refills)
    return
      if startDate is not null and totalDaysSupplied is not null then
        Interval[startDate, startDate + Quantity(totalDaysSupplied - 1, 'day') ]
      else if startDate is not null and boundsPeriod."high" is not null then
        Interval[startDate, date from end of boundsPeriod]
      else
        null

/**********************************************************************/
/* Functions in this region are copied from opioid-mme-r4             */
/**********************************************************************/

define function Quantity(value Decimal, unit String):
  if value is not null then
    System.Quantity { value: value, unit: unit }
  else
    null

/*
 Goal is to get to number of days
 Two broad approaches to the calculation:
  1) Based on supply and frequency, calculate the number of expected days the medication will cover/has covered
  2) Based on relevant period, determine a covered interval and calculate the length of that interval in days
This topic covers several use cases and illustrates how to calculate Cumulative
Medication Duration for each type of medication resource using the supply and
frequency approach.
*/

/*
  For the first approach, we need to get from frequency to a frequency/day
  So we define ToDaily
*/

/*
  Calculates daily frequency given frequency within a period
*/
define function ToDaily(frequency System.Integer, period System.Quantity):
  case period.unit
    when 'h' then frequency * (24.0 / period.value)
    when 'min' then frequency * (24.0 / period.value) * 60
    when 's' then frequency * (24.0 / period.value) * 60 * 60
    when 'd' then frequency * (24.0 / period.value) / 24
    when 'wk' then frequency * (24.0 / period.value) / (24 * 7)
    when 'mo' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'a' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    when 'hour' then frequency * (24.0 / period.value)
    when 'minute' then frequency * (24.0 / period.value) * 60
    when 'second' then frequency * (24.0 / period.value) * 60 * 60
    when 'day' then frequency * (24.0 / period.value) / 24
    when 'week' then frequency * (24.0 / period.value) / (24 * 7)
    when 'month' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'year' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    when 'hours' then frequency * (24.0 / period.value)
    when 'minutes' then frequency * (24.0 / period.value) * 60
    when 'seconds' then frequency * (24.0 / period.value) * 60 * 60
    when 'days' then frequency * (24.0 / period.value) / 24
    when 'weeks' then frequency * (24.0 / period.value) / (24 * 7)
    when 'months' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'years' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    else Message(null, true, 'CMDLogic.ToDaily.UnknownUnit', ErrorLevel, 'Unknown unit ' & period.unit)
  end