Group nodes together based on condition and validate using Schematron - xslt

Question

I am working on writing rules using Schematron to validate data below. The requirement is to verify whether a patient has at least one encounter in the past 12 months. If there are multiple encounters per patient, use the last encounter.
<root>
<entry>
<resource>
<resourceType>Encounter</resourceType>
<subject>
<id>Patient/12345</id>
</subject>
<encounterDate>2018-04-10T10:00:00</encounterDate>
</resource>
</entry>
<entry>
<resource>
<resourceType>Encounter</resourceType>
<subject>
<id>Patient/abcde</id>
</subject>
<encounterDate>2020-04-10T10:00:00</encounterDate>
</resource>
</entry>
<entry>
<resource>
<resourceType>Encounter</resourceType>
<subject>
<id>Patient/abcde</id>
</subject>
<encounterDate>2019-05-10T10:00:00</encounterDate>
</resource>
</entry>
</root>
The above data should pass the validation because the latest encounter is less than a year ago.
What I want to know is, if I write a template that groups encounters together by patient id, is there a way to pass that template to the rule context? If not, is there any other way of doing it?
I am completely new to both xslt and Schematron and here is what I have so far:
<schema xmlns="http://purl.oclc.org/dsdl/schematron" >
<pattern>
<key name="patientId" match="entry" use="/resouce/subject/id/text()"/>
<template name="dateByPatient" match="entry">
<root>
<for-each select="resource/subject/id">
<patient >
<for-each select="key('patientId',text())">
<effectiveDateTime><value-of select="./resource/encounterDate"/></effectiveDateTime>
</for-each>
</patient>
</for-each>
</root>
</template>
<let name="template">
<dateByPatient/>
</let>
<let name="latest">
<root>
<for-each select="$template/root/patient">
<patient >
<sort select="effectiveDateTime" order="descending" />
<if test="position() = 1">
<effectiveDateTime><value-of select="effectiveDateTime" /></effectiveDateTime>
</if>
</patient>
</for-each>
</root>
</let>
<rule context="$latest/root/patient/effectiveDateTime">
<let name="days" value="days-from-duration(fn:current-dateTime() - xs:dateTime(text()))" />
<assert test="days-from-duration(fn:current-dateTime() - xs:dateTime(text())) < 365">
Encounter date more than a year : <value-of select="$days" /> days
</assert>
</rule>
</pattern>
</schema>

Answer 1

With XSLT 3 underlying you could use
<?xml version="1.0" encoding="UTF-8"?>
<sch:schema xmlns:sch="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt3"
xmlns:sqf="http://www.schematron-quickfix.com/validator/process">
<sch:ns prefix="map" uri="http://www.w3.org/2005/xpath-functions/map"/>
<sch:pattern>
<sch:rule context="root">
<sch:let name="groups"
value="let $encounter-resources := entry/resource[resourceType = 'Encounter']
return map:merge(
$encounter-resources
!
map {
data(subject/id) : xs:dateTime(encounterDate)
},
map { 'duplicates' : 'combine' }
)"/>
<sch:assert
test="every $patient in map:keys($groups)
satisfies
(current-dateTime() - max($groups($patient)))
lt xs:dayTimeDuration('P365D')">At least one patient with latest encounter more than a year ago.</sch:assert>
</sch:rule>
</sch:pattern>
</sch:schema>
Or to output more detailed information and to only process resources with type Encounter:
<?xml version="1.0" encoding="UTF-8"?>
<sch:schema xmlns:sch="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt3"
xmlns:sqf="http://www.schematron-quickfix.com/validator/process">
<sch:ns prefix="map" uri="http://www.w3.org/2005/xpath-functions/map"/>
<sch:pattern>
<sch:rule context="root">
<sch:let name="groups"
value="let $encounter-resources := entry/resource[resourceType = 'Encounter']
return map:merge(
$encounter-resources
!
map {
data(subject/id) : xs:dateTime(encounterDate)
},
map { 'duplicates' : 'combine' }
)"/>
<sch:let name="failing-patients"
value="map:keys($groups)[(current-dateTime() - max($groups(.))) gt xs:dayTimeDuration('P365D')]"/>
<sch:report
test="exists($failing-patients)">Patients <sch:value-of select="$failing-patients"/> with latest encounter more than a year ago.</sch:report>
</sch:rule>
</sch:pattern>
</sch:schema>
I don't think you can mix Schematron and XSLT as freely as your code tries, you would need to set up an XProc pipeline to use p:xslt to group the original input and then a validation step to validate with Schematron.
As for your problems to run the second sample with node-schematron, it uses an XPath implementation that doesn't support the XPath 3.1 sort function it seems, node-schematron also fails to handle maps as intermediary results of a Schematron variable, so only stuffing all into one variable expression seems to do; two examples work:
<sch:schema xmlns:sch="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt3"
xmlns:sqf="http://www.schematron-quickfix.com/validator/process">
<sch:ns prefix="map" uri="http://www.w3.org/2005/xpath-functions/map"/>
<sch:pattern>
<sch:rule context="root">
<sch:let name="failing-patients"
value="let $encounter-resources := entry/resource[resourceType = 'Encounter'],
$groups := map:merge(
$encounter-resources
!
map {
data(subject/id) : xs:dateTime(encounterDate)
},
map { 'duplicates' : 'combine' }
)
return map:keys($groups)[(current-dateTime() - max($groups(.))) gt xs:dayTimeDuration('P365D')]"/>
<sch:report
test="exists($failing-patients)">Patients <sch:value-of select="$failing-patients"/> with latest encounter more than a year ago.</sch:report>
</sch:rule>
</sch:pattern>
</sch:schema>
or
<sch:schema xmlns:sch="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt3"
xmlns:sqf="http://www.schematron-quickfix.com/validator/process">
<sch:ns prefix="map" uri="http://www.w3.org/2005/xpath-functions/map"/>
<sch:pattern>
<sch:rule context="root">
<sch:let name="failing-patients"
value="let
$encounter-resources := entry/resource[resourceType = 'Encounter'],
$groups := fold-left(
$encounter-resources,
map{},
function($m, $e) {
map:put(
$m,
data($e/subject/id),
max((xs:dateTime($e/encounterDate), map:get($m, data($e/subject/id))))
)
})
return map:keys($groups)[(current-dateTime() - $groups(.)) gt xs:dayTimeDuration('P365D')]"/>
<sch:report test="exists($failing-patients)">Patients <sch:value-of
select="$failing-patients"/> with latest encounter more than a year
ago.</sch:report>
</sch:rule>
</sch:pattern>
</sch:schema>
If you need an assertion that fails then replace the sch:report with
<sch:assert
test="empty($failing-patients)">Patients <sch:value-of select="$failing-patients"/> with latest encounter more than a year ago.</sch:assert>