Computable Care Guidelines
1.0.1-current - ci-build International flag

Computable Care Guidelines, published by IHE QRPH Technical Committee. This guide is not an authorized publication; it is the continuous build for version 1.0.1-current built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/IHE/QRPH.CCG/ and changes regularly. See the Directory of published versions

Resource Profile: CCG Library for CARDs

Official URL: https://profiles.ihe.net/QRPH/CCG/StructureDefinition/ccg-card-library Version: 1.0.1-current
Active as of 2025-10-06 Computable Name: CCG_CARD_Library

Profile to serve as the basis for all CARD definitions referencing Library resources based on the CPG CQL Library

Usages:

  • This Profile is not used by any profiles in this Implementation Guide

You can also check for usages in the FHIR IG Statistics

Formal Views of Profile Content

Description of Profiles, Differentials, Snapshots and how the different presentations work.

NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Library C 0..* CQLLibrary Represents a library of quality improvement components
Constraints: lib-0, clb-1
... id Σ 1..1 id Logical id of this artifact
... implicitRules ?!Σ 0..1 uri A set of rules under which this content was created
... Slices for extension Content/Rules for all slices
.... extension:cqlOptions S 0..1 (Complex) What options
URL: http://hl7.org/fhir/StructureDefinition/cqf-cqlOptions
..... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/cqf-cqlOptions"
..... value[x] 1..1 Reference(CQL Options) Value of extension
... modifierExtension ?! 0..* Extension Extensions that cannot be ignored
... url Σ 1..1 uri Canonical identifier for this library, represented as a URI (globally unique)
... name ΣC 1..1 string Name for this library (computer friendly)
... title Σ 1..1 string Name for this library (human friendly)
... status ?!Σ 1..1 code draft | active | retired | unknown
Binding: PublicationStatus (required): The lifecycle status of an artifact.
... type Σ 1..1 CodeableConcept logic-library | model-definition | asset-collection | module-definition
Binding: LibraryType (extensible): The type of knowledge asset this library contains.
... subject[x] S 0..1 Type of individual the library content is focused on
Binding: SubjectType (extensible): The possible types of subjects for a library (E.g. Patient, Practitioner, Organization, Location, etc.).
.... subjectCodeableConcept CodeableConcept
.... subjectReference Reference(Group)
... date Σ 1..1 dateTime Date last changed
... publisher Σ 1..1 string Name of the publisher (organization or individual)
... content SΣC 1..* Attachment Contents of the library, either embedded or referenced
Constraints: clb-2
.... contentType SΣC 1..1 code Mime type of the content, with charset etc.
Binding: Mime Types (required): The mime type of an attachment. Any valid mime type is allowed.
Example General: text/plain; charset=UTF-8, image/png
.... data SC 0..1 base64Binary Data inline, base64ed
.... url SΣC 0..1 url Uri where the data can be found
Example General: http://www.acme.com/logo-small.png

doco Documentation for this format

Terminology Bindings

Path Status Usage ValueSet Version Source
Library.status Base required PublicationStatus 📍4.0.1 FHIR Std.
Library.type Base extensible LibraryType 📦4.0.1 FHIR Std.
Library.subject[x] Base extensible Subject type 📦4.0.1 FHIR Std.
Library.content.contentType Base required MimeType 📍4.0.1 FHIR Std.

Constraints

Id Grade Path(s) Description Expression
clb-1 error Library CQL libraries must one (and only one) content element that starts with 'text/cql' content.where(contentType.startsWith('text/cql')).count() = 1
clb-2 error Library.content CQL libraries must have a content element with data or a url (or both) data.exists() or url.exists()
dom-2 error Library If the resource is contained in another resource, it SHALL NOT contain nested Resources contained.contained.empty()
dom-3 error Library If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().as(canonical) | %resource.descendants().as(uri) | %resource.descendants().as(url))) or descendants().where(reference = '#').exists() or descendants().where(as(canonical) = '#').exists() or descendants().where(as(canonical) = '#').exists()).not()).trace('unmatched', id).empty()
dom-4 error Library If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated contained.meta.versionId.empty() and contained.meta.lastUpdated.empty()
dom-5 error Library If a resource is contained in another resource, it SHALL NOT have a security label contained.meta.security.empty()
dom-6 best practice Library A resource should have narrative for robust management text.`div`.exists()
ele-1 error **ALL** elements All FHIR elements must have a @value or children hasValue() or (children().count() > id.count())
ext-1 error **ALL** extensions Must have either extensions or value[x], not both extension.exists() != value.exists()
lib-0 warning Library Name should be usable as an identifier for the module by machine processing applications such as code generation name.matches('[A-Z]([A-Za-z0-9_]){0,254}')

This structure is derived from CQLLibrary

NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Library 0..* CQLLibrary Represents a library of quality improvement components
... id 1..1 id Logical id of this artifact
... url 1..1 uri Canonical identifier for this library, represented as a URI (globally unique)
... name 1..1 string Name for this library (computer friendly)
... title 1..1 string Name for this library (human friendly)
... date 1..1 dateTime Date last changed
... publisher 1..1 string Name of the publisher (organization or individual)

doco Documentation for this format
NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Library C 0..* CQLLibrary Represents a library of quality improvement components
Constraints: lib-0, clb-1
... id Σ 1..1 id Logical id of this artifact
... meta Σ 0..1 Meta Metadata about the resource
... implicitRules ?!Σ 0..1 uri A set of rules under which this content was created
... language 0..1 code Language of the resource content
Binding: CommonLanguages (preferred): A human language.
Additional BindingsPurpose
AllLanguages Max Binding
... text 0..1 Narrative Text summary of the resource, for human interpretation
This profile does not constrain the narrative in regard to content, language, or traceability to data elements
... contained 0..* Resource Contained, inline Resources
... Slices for extension 0..* Extension Extension
Slice: Unordered, Open by value:url
.... extension:cqlOptions S 0..1 (Complex) What options
URL: http://hl7.org/fhir/StructureDefinition/cqf-cqlOptions
..... id 0..1 id Unique id for inter-element referencing
..... extension 0..* Extension Additional content defined by implementations
Slice: Unordered, Open by value:url
..... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/cqf-cqlOptions"
..... value[x] 1..1 Reference(CQL Options) Value of extension
... modifierExtension ?! 0..* Extension Extensions that cannot be ignored
... url Σ 1..1 uri Canonical identifier for this library, represented as a URI (globally unique)
... identifier Σ 0..* Identifier Additional identifier for the library
... version Σ 0..1 string Business version of the library
... name ΣC 1..1 string Name for this library (computer friendly)
... title Σ 1..1 string Name for this library (human friendly)
... subtitle 0..1 string Subordinate title of the library
... status ?!Σ 1..1 code draft | active | retired | unknown
Binding: PublicationStatus (required): The lifecycle status of an artifact.
... experimental Σ 0..1 boolean For testing purposes, not real usage
... type Σ 1..1 CodeableConcept logic-library | model-definition | asset-collection | module-definition
Binding: LibraryType (extensible): The type of knowledge asset this library contains.
... subject[x] S 0..1 Type of individual the library content is focused on
Binding: SubjectType (extensible): The possible types of subjects for a library (E.g. Patient, Practitioner, Organization, Location, etc.).
.... subjectCodeableConcept CodeableConcept
.... subjectReference Reference(Group)
... date Σ 1..1 dateTime Date last changed
... publisher Σ 1..1 string Name of the publisher (organization or individual)
... contact Σ 0..* ContactDetail Contact details for the publisher
... description Σ 0..1 markdown Natural language description of the library
... useContext Σ 0..* UsageContext The context that the content is intended to support
... jurisdiction Σ 0..* CodeableConcept Intended jurisdiction for library (if applicable)
Binding: Jurisdiction ValueSet (extensible): Countries and regions within which this artifact is targeted for use.
... purpose 0..1 markdown Why this library is defined
... usage 0..1 string Describes the clinical usage of the library
... copyright 0..1 markdown Use and/or publishing restrictions
... approvalDate 0..1 date When the library was approved by publisher
... lastReviewDate 0..1 date When the library was last reviewed
... effectivePeriod Σ 0..1 Period When the library is expected to be used
... topic 0..* CodeableConcept E.g. Education, Treatment, Assessment, etc.
Binding: DefinitionTopic (example): High-level categorization of the definition, used for searching, sorting, and filtering.
... author 0..* ContactDetail Who authored the content
... editor 0..* ContactDetail Who edited the content
... reviewer 0..* ContactDetail Who reviewed the content
... endorser 0..* ContactDetail Who endorsed the content
... relatedArtifact 0..* RelatedArtifact Additional documentation, citations, etc.
... parameter 0..* ParameterDefinition Parameters defined by the library
... dataRequirement 0..* DataRequirement What data is referenced by this library
... content SΣC 1..* Attachment Contents of the library, either embedded or referenced
Constraints: clb-2
.... id 0..1 string Unique id for inter-element referencing
.... extension 0..* Extension Additional content defined by implementations
Slice: Unordered, Open by value:url
.... contentType SΣC 1..1 code Mime type of the content, with charset etc.
Binding: Mime Types (required): The mime type of an attachment. Any valid mime type is allowed.
Example General: text/plain; charset=UTF-8, image/png
.... language Σ 0..1 code Human language of the content (BCP-47)
Binding: CommonLanguages (preferred): A human language.
Additional BindingsPurpose
AllLanguages Max Binding

Example General: en-AU
.... data SC 0..1 base64Binary Data inline, base64ed
.... url SΣC 0..1 url Uri where the data can be found
Example General: http://www.acme.com/logo-small.png
.... size Σ 0..1 unsignedInt Number of bytes of content (if url provided)
.... hash Σ 0..1 base64Binary Hash of the data (sha-1, base64ed)
.... title Σ 0..1 string Label to display in place of the data
Example General: Official Corporate Logo
.... creation Σ 0..1 dateTime Date attachment was first created

doco Documentation for this format

Terminology Bindings

Path Status Usage ValueSet Version Source
Library.language Base preferred Common Languages 📦4.0.1 FHIR Std.
Library.status Base required PublicationStatus 📍4.0.1 FHIR Std.
Library.type Base extensible LibraryType 📦4.0.1 FHIR Std.
Library.subject[x] Base extensible Subject type 📦4.0.1 FHIR Std.
Library.jurisdiction Base extensible Jurisdiction 📦4.0.1 FHIR Std.
Library.topic Base example DefinitionTopic 📦4.0.1 FHIR Std.
Library.content.contentType Base required MimeType 📍4.0.1 FHIR Std.
Library.content.language Base preferred Common Languages 📦4.0.1 FHIR Std.

Constraints

Id Grade Path(s) Description Expression
clb-1 error Library CQL libraries must one (and only one) content element that starts with 'text/cql' content.where(contentType.startsWith('text/cql')).count() = 1
clb-2 error Library.content CQL libraries must have a content element with data or a url (or both) data.exists() or url.exists()
dom-2 error Library If the resource is contained in another resource, it SHALL NOT contain nested Resources contained.contained.empty()
dom-3 error Library If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().as(canonical) | %resource.descendants().as(uri) | %resource.descendants().as(url))) or descendants().where(reference = '#').exists() or descendants().where(as(canonical) = '#').exists() or descendants().where(as(canonical) = '#').exists()).not()).trace('unmatched', id).empty()
dom-4 error Library If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated contained.meta.versionId.empty() and contained.meta.lastUpdated.empty()
dom-5 error Library If a resource is contained in another resource, it SHALL NOT have a security label contained.meta.security.empty()
dom-6 best practice Library A resource should have narrative for robust management text.`div`.exists()
ele-1 error **ALL** elements All FHIR elements must have a @value or children hasValue() or (children().count() > id.count())
ext-1 error **ALL** extensions Must have either extensions or value[x], not both extension.exists() != value.exists()
lib-0 warning Library Name should be usable as an identifier for the module by machine processing applications such as code generation name.matches('[A-Z]([A-Za-z0-9_]){0,254}')

This structure is derived from CQLLibrary

Summary

Mandatory: 6 elements

Key Elements View

NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Library C 0..* CQLLibrary Represents a library of quality improvement components
Constraints: lib-0, clb-1
... id Σ 1..1 id Logical id of this artifact
... implicitRules ?!Σ 0..1 uri A set of rules under which this content was created
... Slices for extension Content/Rules for all slices
.... extension:cqlOptions S 0..1 (Complex) What options
URL: http://hl7.org/fhir/StructureDefinition/cqf-cqlOptions
..... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/cqf-cqlOptions"
..... value[x] 1..1 Reference(CQL Options) Value of extension
... modifierExtension ?! 0..* Extension Extensions that cannot be ignored
... url Σ 1..1 uri Canonical identifier for this library, represented as a URI (globally unique)
... name ΣC 1..1 string Name for this library (computer friendly)
... title Σ 1..1 string Name for this library (human friendly)
... status ?!Σ 1..1 code draft | active | retired | unknown
Binding: PublicationStatus (required): The lifecycle status of an artifact.
... type Σ 1..1 CodeableConcept logic-library | model-definition | asset-collection | module-definition
Binding: LibraryType (extensible): The type of knowledge asset this library contains.
... subject[x] S 0..1 Type of individual the library content is focused on
Binding: SubjectType (extensible): The possible types of subjects for a library (E.g. Patient, Practitioner, Organization, Location, etc.).
.... subjectCodeableConcept CodeableConcept
.... subjectReference Reference(Group)
... date Σ 1..1 dateTime Date last changed
... publisher Σ 1..1 string Name of the publisher (organization or individual)
... content SΣC 1..* Attachment Contents of the library, either embedded or referenced
Constraints: clb-2
.... contentType SΣC 1..1 code Mime type of the content, with charset etc.
Binding: Mime Types (required): The mime type of an attachment. Any valid mime type is allowed.
Example General: text/plain; charset=UTF-8, image/png
.... data SC 0..1 base64Binary Data inline, base64ed
.... url SΣC 0..1 url Uri where the data can be found
Example General: http://www.acme.com/logo-small.png

doco Documentation for this format

Terminology Bindings

Path Status Usage ValueSet Version Source
Library.status Base required PublicationStatus 📍4.0.1 FHIR Std.
Library.type Base extensible LibraryType 📦4.0.1 FHIR Std.
Library.subject[x] Base extensible Subject type 📦4.0.1 FHIR Std.
Library.content.contentType Base required MimeType 📍4.0.1 FHIR Std.

Constraints

Id Grade Path(s) Description Expression
clb-1 error Library CQL libraries must one (and only one) content element that starts with 'text/cql' content.where(contentType.startsWith('text/cql')).count() = 1
clb-2 error Library.content CQL libraries must have a content element with data or a url (or both) data.exists() or url.exists()
dom-2 error Library If the resource is contained in another resource, it SHALL NOT contain nested Resources contained.contained.empty()
dom-3 error Library If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().as(canonical) | %resource.descendants().as(uri) | %resource.descendants().as(url))) or descendants().where(reference = '#').exists() or descendants().where(as(canonical) = '#').exists() or descendants().where(as(canonical) = '#').exists()).not()).trace('unmatched', id).empty()
dom-4 error Library If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated contained.meta.versionId.empty() and contained.meta.lastUpdated.empty()
dom-5 error Library If a resource is contained in another resource, it SHALL NOT have a security label contained.meta.security.empty()
dom-6 best practice Library A resource should have narrative for robust management text.`div`.exists()
ele-1 error **ALL** elements All FHIR elements must have a @value or children hasValue() or (children().count() > id.count())
ext-1 error **ALL** extensions Must have either extensions or value[x], not both extension.exists() != value.exists()
lib-0 warning Library Name should be usable as an identifier for the module by machine processing applications such as code generation name.matches('[A-Z]([A-Za-z0-9_]){0,254}')

Differential View

This structure is derived from CQLLibrary

NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Library 0..* CQLLibrary Represents a library of quality improvement components
... id 1..1 id Logical id of this artifact
... url 1..1 uri Canonical identifier for this library, represented as a URI (globally unique)
... name 1..1 string Name for this library (computer friendly)
... title 1..1 string Name for this library (human friendly)
... date 1..1 dateTime Date last changed
... publisher 1..1 string Name of the publisher (organization or individual)

doco Documentation for this format

Snapshot View

NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Library C 0..* CQLLibrary Represents a library of quality improvement components
Constraints: lib-0, clb-1
... id Σ 1..1 id Logical id of this artifact
... meta Σ 0..1 Meta Metadata about the resource
... implicitRules ?!Σ 0..1 uri A set of rules under which this content was created
... language 0..1 code Language of the resource content
Binding: CommonLanguages (preferred): A human language.
Additional BindingsPurpose
AllLanguages Max Binding
... text 0..1 Narrative Text summary of the resource, for human interpretation
This profile does not constrain the narrative in regard to content, language, or traceability to data elements
... contained 0..* Resource Contained, inline Resources
... Slices for extension 0..* Extension Extension
Slice: Unordered, Open by value:url
.... extension:cqlOptions S 0..1 (Complex) What options
URL: http://hl7.org/fhir/StructureDefinition/cqf-cqlOptions
..... id 0..1 id Unique id for inter-element referencing
..... extension 0..* Extension Additional content defined by implementations
Slice: Unordered, Open by value:url
..... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/cqf-cqlOptions"
..... value[x] 1..1 Reference(CQL Options) Value of extension
... modifierExtension ?! 0..* Extension Extensions that cannot be ignored
... url Σ 1..1 uri Canonical identifier for this library, represented as a URI (globally unique)
... identifier Σ 0..* Identifier Additional identifier for the library
... version Σ 0..1 string Business version of the library
... name ΣC 1..1 string Name for this library (computer friendly)
... title Σ 1..1 string Name for this library (human friendly)
... subtitle 0..1 string Subordinate title of the library
... status ?!Σ 1..1 code draft | active | retired | unknown
Binding: PublicationStatus (required): The lifecycle status of an artifact.
... experimental Σ 0..1 boolean For testing purposes, not real usage
... type Σ 1..1 CodeableConcept logic-library | model-definition | asset-collection | module-definition
Binding: LibraryType (extensible): The type of knowledge asset this library contains.
... subject[x] S 0..1 Type of individual the library content is focused on
Binding: SubjectType (extensible): The possible types of subjects for a library (E.g. Patient, Practitioner, Organization, Location, etc.).
.... subjectCodeableConcept CodeableConcept
.... subjectReference Reference(Group)
... date Σ 1..1 dateTime Date last changed
... publisher Σ 1..1 string Name of the publisher (organization or individual)
... contact Σ 0..* ContactDetail Contact details for the publisher
... description Σ 0..1 markdown Natural language description of the library
... useContext Σ 0..* UsageContext The context that the content is intended to support
... jurisdiction Σ 0..* CodeableConcept Intended jurisdiction for library (if applicable)
Binding: Jurisdiction ValueSet (extensible): Countries and regions within which this artifact is targeted for use.
... purpose 0..1 markdown Why this library is defined
... usage 0..1 string Describes the clinical usage of the library
... copyright 0..1 markdown Use and/or publishing restrictions
... approvalDate 0..1 date When the library was approved by publisher
... lastReviewDate 0..1 date When the library was last reviewed
... effectivePeriod Σ 0..1 Period When the library is expected to be used
... topic 0..* CodeableConcept E.g. Education, Treatment, Assessment, etc.
Binding: DefinitionTopic (example): High-level categorization of the definition, used for searching, sorting, and filtering.
... author 0..* ContactDetail Who authored the content
... editor 0..* ContactDetail Who edited the content
... reviewer 0..* ContactDetail Who reviewed the content
... endorser 0..* ContactDetail Who endorsed the content
... relatedArtifact 0..* RelatedArtifact Additional documentation, citations, etc.
... parameter 0..* ParameterDefinition Parameters defined by the library
... dataRequirement 0..* DataRequirement What data is referenced by this library
... content SΣC 1..* Attachment Contents of the library, either embedded or referenced
Constraints: clb-2
.... id 0..1 string Unique id for inter-element referencing
.... extension 0..* Extension Additional content defined by implementations
Slice: Unordered, Open by value:url
.... contentType SΣC 1..1 code Mime type of the content, with charset etc.
Binding: Mime Types (required): The mime type of an attachment. Any valid mime type is allowed.
Example General: text/plain; charset=UTF-8, image/png
.... language Σ 0..1 code Human language of the content (BCP-47)
Binding: CommonLanguages (preferred): A human language.
Additional BindingsPurpose
AllLanguages Max Binding

Example General: en-AU
.... data SC 0..1 base64Binary Data inline, base64ed
.... url SΣC 0..1 url Uri where the data can be found
Example General: http://www.acme.com/logo-small.png
.... size Σ 0..1 unsignedInt Number of bytes of content (if url provided)
.... hash Σ 0..1 base64Binary Hash of the data (sha-1, base64ed)
.... title Σ 0..1 string Label to display in place of the data
Example General: Official Corporate Logo
.... creation Σ 0..1 dateTime Date attachment was first created

doco Documentation for this format

Terminology Bindings

Path Status Usage ValueSet Version Source
Library.language Base preferred Common Languages 📦4.0.1 FHIR Std.
Library.status Base required PublicationStatus 📍4.0.1 FHIR Std.
Library.type Base extensible LibraryType 📦4.0.1 FHIR Std.
Library.subject[x] Base extensible Subject type 📦4.0.1 FHIR Std.
Library.jurisdiction Base extensible Jurisdiction 📦4.0.1 FHIR Std.
Library.topic Base example DefinitionTopic 📦4.0.1 FHIR Std.
Library.content.contentType Base required MimeType 📍4.0.1 FHIR Std.
Library.content.language Base preferred Common Languages 📦4.0.1 FHIR Std.

Constraints

Id Grade Path(s) Description Expression
clb-1 error Library CQL libraries must one (and only one) content element that starts with 'text/cql' content.where(contentType.startsWith('text/cql')).count() = 1
clb-2 error Library.content CQL libraries must have a content element with data or a url (or both) data.exists() or url.exists()
dom-2 error Library If the resource is contained in another resource, it SHALL NOT contain nested Resources contained.contained.empty()
dom-3 error Library If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().as(canonical) | %resource.descendants().as(uri) | %resource.descendants().as(url))) or descendants().where(reference = '#').exists() or descendants().where(as(canonical) = '#').exists() or descendants().where(as(canonical) = '#').exists()).not()).trace('unmatched', id).empty()
dom-4 error Library If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated contained.meta.versionId.empty() and contained.meta.lastUpdated.empty()
dom-5 error Library If a resource is contained in another resource, it SHALL NOT have a security label contained.meta.security.empty()
dom-6 best practice Library A resource should have narrative for robust management text.`div`.exists()
ele-1 error **ALL** elements All FHIR elements must have a @value or children hasValue() or (children().count() > id.count())
ext-1 error **ALL** extensions Must have either extensions or value[x], not both extension.exists() != value.exists()
lib-0 warning Library Name should be usable as an identifier for the module by machine processing applications such as code generation name.matches('[A-Z]([A-Za-z0-9_]){0,254}')

This structure is derived from CQLLibrary

Summary

Mandatory: 6 elements

 

Other representations of profile: CSV, Excel, Schematron