Extension-derivation-reference.xml

This page is part of the FHIR Specification (v5.0.0-ballot: FHIR R5 Ballot Preview). The current version which supercedes this version is 5.0.0. For a full list of available versions, see the Directory of published versions
Example StructureDefinition/derivation-reference (XML)

FHIR Infrastructure Work Group
Maturity Level: N/A
Standards Status: Informative
Raw XML (canonical form + also see XML Format Specification)
DerivationReference
<?xml version="1.0" encoding="UTF-8"?>

<StructureDefinition xmlns="http://hl7.org/fhir">
  <id value="derivation-reference"/> 
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-wg">
    <valueCode value="fhir"/> 
  </extension> 
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm">
    <valueInteger value="0"/> 
  </extension> 
  <url value="http://hl7.org/fhir/StructureDefinition/derivation-reference"/> 
  <identifier> 
    <system value="urn:ietf:rfc:3986"/> 
    <value value="urn:oid:2.16.840.1.113883.4.642.5.1425"/> 
  </identifier> 
  <version value="5.0.0-ballot"/> 
  <name value="DerivationReference"/> 
  <title value="Derivation Reference"/> 
  <status value="draft"/> 
  <experimental value="false"/> 
  <date value="2020-01-18"/> 
  <publisher value="HL7"/> 
  <description value="References a location within a set of source text from which the discrete information
   described by this Resource/Element was extracted."/> 
  <fhirVersion value="5.0.0"/> 
  <mapping> 
    <identity value="rim"/> 
    <uri value="http://hl7.org/v3"/> 
    <name value="RIM Mapping"/> 
  </mapping> 
  <kind value="complex-type"/> 
  <abstract value="false"/> 
  <context> 
    <type value="element"/> 
    <expression value="Resource"/> 
  </context> 
  <context> 
    <type value="element"/> 
    <expression value="Element"/> 
  </context> 
  <type value="Extension"/> 
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
  <derivation value="constraint"/> 
  <snapshot> 
    <element id="Extension">
      <path value="Extension"/> 
      <short value="References a location within a set of source text from which the discrete information
       described by this Resource/Element was extracted."/> 
      <definition value="References a location within a set of source text from which the discrete information
       described by this Resource/Element was extracted."/> 
      <min value="0"/> 
      <max value="*"/> 
      <base> 
        <path value="Extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), 'value')])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <constraint> 
        <key value="der-1"/> 
        <severity value="error"/> 
        <human value="Cannot have length if offset is missing."/> 
        <expression value="extension.where(url='length').exists() implies extension.where(url='offset').exists()"/> 
        <xpath value="todo-remove-this-line-when-build-process-allows-that"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/derivation-reference"/> 
      </constraint> 
      <isModifier value="false"/> 
    </element> 
    <element id="Extension.id">
      <path value="Extension.id"/> 
      <representation value="xmlAttr"/> 
      <short value="Unique id for inter-element referencing"/> 
      <definition value="Unique id for the element within a resource (for internal references). This may be any
       string value that does not contain spaces."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.id"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="id"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension">
      <path value="Extension.extension"/> 
      <slicing> 
        <discriminator> 
          <type value="value"/> 
          <path value="url"/> 
        </discriminator> 
        <description value="Extensions are always sliced by (at least) url"/> 
        <rules value="open"/> 
      </slicing> 
      <short value="Additional content defined by implementations"/> 
      <definition value="May be used to represent additional information that is not part of the basic definition
       of the element. To make the use of extensions safe and manageable, there is a strict set
       of governance  applied to the definition and use of extensions. Though any implementer
       can define an extension, there is a set of requirements that SHALL be met as part of the
       definition of the extension."/> 
      <comment value="There can be no stigma associated with the use of extensions by any application, project,
       or standard - regardless of the institution or jurisdiction that uses or defines the extensions.
        The use of extensions is what allows the FHIR specification to retain a core level of
       simplicity for everyone."/> 
      <alias value="extensions"/> 
      <alias value="user content"/> 
      <min value="0"/> 
      <max value="*"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:reference">
      <path value="Extension.extension"/> 
      <sliceName value="reference"/> 
      <short value="Source reference."/> 
      <definition value="References a location within a set of source text from which the discrete information
       described by this Resource/Element was extracted."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
    </element> 
    <element id="Extension.extension:reference.id">
      <path value="Extension.extension.id"/> 
      <representation value="xmlAttr"/> 
      <short value="Unique id for inter-element referencing"/> 
      <definition value="Unique id for the element within a resource (for internal references). This may be any
       string value that does not contain spaces."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.id"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="id"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:reference.extension">
      <path value="Extension.extension.extension"/> 
      <slicing> 
        <discriminator> 
          <type value="value"/> 
          <path value="url"/> 
        </discriminator> 
        <description value="Extensions are always sliced by (at least) url"/> 
        <rules value="open"/> 
      </slicing> 
      <short value="Extension"/> 
      <definition value="An Extension"/> 
      <min value="0"/> 
      <max value="0"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
    </element> 
    <element id="Extension.extension:reference.url">
      <path value="Extension.extension.url"/> 
      <representation value="xmlAttr"/> 
      <short value="identifies the meaning of the extension"/> 
      <definition value="Source of the definition for the extension code - a logical name or a URL."/> 
      <comment value="The definition may point directly to a computable or human-readable definition of the
       extensibility codes, or it may be a logical URI as declared in some other specification.
       The definition SHALL be a URI for the Structure Definition defining the extension."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.url"/> 
        <min value="1"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="uri"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <fixedUri value="reference"/> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:reference.value[x]">
      <path value="Extension.extension.value[x]"/> 
      <short value="Value of extension"/> 
      <definition value="Value of extension - must be one of a constrained set of the data types (see [Extensibility](extensi
      bility.html) for a list)."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.value[x]"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <code value="Reference"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:path">
      <path value="Extension.extension"/> 
      <sliceName value="path"/> 
      <short value="Element containing text."/> 
      <definition value="Corresponds to the element within the resource containing the text."/> 
      <comment value="Follows the FHIRPath expression syntax used for OperationOutcome. If not present, then
       the resource must either be a Binary or a DocumentReference (with a single content element)
       and the content is the text represented by the instance or the attachment.  If the DocumentReference
       has more than one 'content', then this path element SHALL be present to distinguish which
       repetition the derivation occurred from."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
    </element> 
    <element id="Extension.extension:path.id">
      <path value="Extension.extension.id"/> 
      <representation value="xmlAttr"/> 
      <short value="Unique id for inter-element referencing"/> 
      <definition value="Unique id for the element within a resource (for internal references). This may be any
       string value that does not contain spaces."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.id"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="id"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:path.extension">
      <path value="Extension.extension.extension"/> 
      <slicing> 
        <discriminator> 
          <type value="value"/> 
          <path value="url"/> 
        </discriminator> 
        <description value="Extensions are always sliced by (at least) url"/> 
        <rules value="open"/> 
      </slicing> 
      <short value="Extension"/> 
      <definition value="An Extension"/> 
      <min value="0"/> 
      <max value="0"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
    </element> 
    <element id="Extension.extension:path.url">
      <path value="Extension.extension.url"/> 
      <representation value="xmlAttr"/> 
      <short value="identifies the meaning of the extension"/> 
      <definition value="Source of the definition for the extension code - a logical name or a URL."/> 
      <comment value="The definition may point directly to a computable or human-readable definition of the
       extensibility codes, or it may be a logical URI as declared in some other specification.
       The definition SHALL be a URI for the Structure Definition defining the extension."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.url"/> 
        <min value="1"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="uri"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <fixedUri value="path"/> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:path.value[x]">
      <path value="Extension.extension.value[x]"/> 
      <short value="Value of extension"/> 
      <definition value="Value of extension - must be one of a constrained set of the data types (see [Extensibility](extensi
      bility.html) for a list)."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.value[x]"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <code value="string"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:offset">
      <path value="Extension.extension"/> 
      <sliceName value="offset"/> 
      <short value="Starting position."/> 
      <definition value="Indicates the starting position (as a count of characters) within the text where the relevant
       derivation began."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
    </element> 
    <element id="Extension.extension:offset.id">
      <path value="Extension.extension.id"/> 
      <representation value="xmlAttr"/> 
      <short value="Unique id for inter-element referencing"/> 
      <definition value="Unique id for the element within a resource (for internal references). This may be any
       string value that does not contain spaces."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.id"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="id"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:offset.extension">
      <path value="Extension.extension.extension"/> 
      <slicing> 
        <discriminator> 
          <type value="value"/> 
          <path value="url"/> 
        </discriminator> 
        <description value="Extensions are always sliced by (at least) url"/> 
        <rules value="open"/> 
      </slicing> 
      <short value="Extension"/> 
      <definition value="An Extension"/> 
      <min value="0"/> 
      <max value="0"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
    </element> 
    <element id="Extension.extension:offset.url">
      <path value="Extension.extension.url"/> 
      <representation value="xmlAttr"/> 
      <short value="identifies the meaning of the extension"/> 
      <definition value="Source of the definition for the extension code - a logical name or a URL."/> 
      <comment value="The definition may point directly to a computable or human-readable definition of the
       extensibility codes, or it may be a logical URI as declared in some other specification.
       The definition SHALL be a URI for the Structure Definition defining the extension."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.url"/> 
        <min value="1"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="uri"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <fixedUri value="offset"/> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:offset.value[x]">
      <path value="Extension.extension.value[x]"/> 
      <short value="Value of extension"/> 
      <definition value="Value of extension - must be one of a constrained set of the data types (see [Extensibility](extensi
      bility.html) for a list)."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.value[x]"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <code value="integer"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:length">
      <path value="Extension.extension"/> 
      <sliceName value="length"/> 
      <short value="Number of characters."/> 
      <definition value="Indicates the number of characters following the start position/beginning of the document
       that was used as part of the derivation process."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
    </element> 
    <element id="Extension.extension:length.id">
      <path value="Extension.extension.id"/> 
      <representation value="xmlAttr"/> 
      <short value="Unique id for inter-element referencing"/> 
      <definition value="Unique id for the element within a resource (for internal references). This may be any
       string value that does not contain spaces."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Element.id"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="id"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:length.extension">
      <path value="Extension.extension.extension"/> 
      <slicing> 
        <discriminator> 
          <type value="value"/> 
          <path value="url"/> 
        </discriminator> 
        <description value="Extensions are always sliced by (at least) url"/> 
        <rules value="open"/> 
      </slicing> 
      <short value="Extension"/> 
      <definition value="An Extension"/> 
      <min value="0"/> 
      <max value="0"/> 
      <base> 
        <path value="Element.extension"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <type> 
        <code value="Extension"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
    </element> 
    <element id="Extension.extension:length.url">
      <path value="Extension.extension.url"/> 
      <representation value="xmlAttr"/> 
      <short value="identifies the meaning of the extension"/> 
      <definition value="Source of the definition for the extension code - a logical name or a URL."/> 
      <comment value="The definition may point directly to a computable or human-readable definition of the
       extensibility codes, or it may be a logical URI as declared in some other specification.
       The definition SHALL be a URI for the Structure Definition defining the extension."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.url"/> 
        <min value="1"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="uri"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <fixedUri value="length"/> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.extension:length.value[x]">
      <path value="Extension.extension.value[x]"/> 
      <short value="Value of extension"/> 
      <definition value="Value of extension - must be one of a constrained set of the data types (see [Extensibility](extensi
      bility.html) for a list)."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.value[x]"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <code value="integer"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.url">
      <path value="Extension.url"/> 
      <representation value="xmlAttr"/> 
      <short value="identifies the meaning of the extension"/> 
      <definition value="Source of the definition for the extension code - a logical name or a URL."/> 
      <comment value="The definition may point directly to a computable or human-readable definition of the
       extensibility codes, or it may be a logical URI as declared in some other specification.
       The definition SHALL be a URI for the Structure Definition defining the extension."/> 
      <min value="1"/> 
      <max value="1"/> 
      <base> 
        <path value="Extension.url"/> 
        <min value="1"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="uri"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <fixedUri value="http://hl7.org/fhir/StructureDefinition/derivation-reference"/> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
    <element id="Extension.value[x]">
      <path value="Extension.value[x]"/> 
      <short value="Value of extension"/> 
      <definition value="Value of extension - must be one of a constrained set of the data types (see [Extensibility](extensi
      bility.html) for a list)."/> 
      <min value="0"/> 
      <max value="0"/> 
      <base> 
        <path value="Extension.value[x]"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <code value="base64Binary"/> 
      </type> 
      <type> 
        <code value="boolean"/> 
      </type> 
      <type> 
        <code value="canonical"/> 
      </type> 
      <type> 
        <code value="code"/> 
      </type> 
      <type> 
        <code value="date"/> 
      </type> 
      <type> 
        <code value="dateTime"/> 
      </type> 
      <type> 
        <code value="decimal"/> 
      </type> 
      <type> 
        <code value="id"/> 
      </type> 
      <type> 
        <code value="instant"/> 
      </type> 
      <type> 
        <code value="integer"/> 
      </type> 
      <type> 
        <code value="integer64"/> 
      </type> 
      <type> 
        <code value="markdown"/> 
      </type> 
      <type> 
        <code value="oid"/> 
      </type> 
      <type> 
        <code value="positiveInt"/> 
      </type> 
      <type> 
        <code value="string"/> 
      </type> 
      <type> 
        <code value="time"/> 
      </type> 
      <type> 
        <code value="unsignedInt"/> 
      </type> 
      <type> 
        <code value="uri"/> 
      </type> 
      <type> 
        <code value="url"/> 
      </type> 
      <type> 
        <code value="uuid"/> 
      </type> 
      <type> 
        <code value="Address"/> 
      </type> 
      <type> 
        <code value="Age"/> 
      </type> 
      <type> 
        <code value="Annotation"/> 
      </type> 
      <type> 
        <code value="Attachment"/> 
      </type> 
      <type> 
        <code value="CodeableConcept"/> 
      </type> 
      <type> 
        <code value="CodeableReference"/> 
      </type> 
      <type> 
        <code value="Coding"/> 
      </type> 
      <type> 
        <code value="ContactPoint"/> 
      </type> 
      <type> 
        <code value="Count"/> 
      </type> 
      <type> 
        <code value="Distance"/> 
      </type> 
      <type> 
        <code value="Duration"/> 
      </type> 
      <type> 
        <code value="HumanName"/> 
      </type> 
      <type> 
        <code value="Identifier"/> 
      </type> 
      <type> 
        <code value="Money"/> 
      </type> 
      <type> 
        <code value="Period"/> 
      </type> 
      <type> 
        <code value="Quantity"/> 
      </type> 
      <type> 
        <code value="Range"/> 
      </type> 
      <type> 
        <code value="Ratio"/> 
      </type> 
      <type> 
        <code value="RatioRange"/> 
      </type> 
      <type> 
        <code value="Reference"/> 
      </type> 
      <type> 
        <code value="SampledData"/> 
      </type> 
      <type> 
        <code value="Signature"/> 
      </type> 
      <type> 
        <code value="Timing"/> 
      </type> 
      <type> 
        <code value="ContactDetail"/> 
      </type> 
      <type> 
        <code value="DataRequirement"/> 
      </type> 
      <type> 
        <code value="Expression"/> 
      </type> 
      <type> 
        <code value="ParameterDefinition"/> 
      </type> 
      <type> 
        <code value="RelatedArtifact"/> 
      </type> 
      <type> 
        <code value="TriggerDefinition"/> 
      </type> 
      <type> 
        <code value="UsageContext"/> 
      </type> 
      <type> 
        <code value="Availability"/> 
      </type> 
      <type> 
        <code value="ExtendedContactDetail"/> 
      </type> 
      <type> 
        <code value="Dosage"/> 
      </type> 
      <type> 
        <code value="Meta"/> 
      </type> 
      <constraint> 
        <key value="ele-1"/> 
        <severity value="error"/> 
        <human value="All FHIR elements must have a @value or children"/> 
        <expression value="hasValue() or (children().count() &gt; id.count())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="N/A"/> 
      </mapping> 
    </element> 
  </snapshot> 
  <differential> 
    <element id="Extension">
      <path value="Extension"/> 
      <short value="References a location within a set of source text from which the discrete information
       described by this Resource/Element was extracted."/> 
      <definition value="References a location within a set of source text from which the discrete information
       described by this Resource/Element was extracted."/> 
      <constraint> 
        <key value="der-1"/> 
        <severity value="error"/> 
        <human value="Cannot have length if offset is missing."/> 
        <expression value="extension.where(url='length').exists() implies extension.where(url='offset').exists()"/> 
        <xpath value="todo-remove-this-line-when-build-process-allows-that"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/derivation-reference"/> 
      </constraint> 
    </element> 
    <element id="Extension.extension:reference">
      <path value="Extension.extension"/> 
      <sliceName value="reference"/> 
      <short value="Source reference."/> 
      <definition value="References a location within a set of source text from which the discrete information
       described by this Resource/Element was extracted."/> 
      <min value="0"/> 
      <max value="1"/> 
    </element> 
    <element id="Extension.extension:reference.extension">
      <path value="Extension.extension.extension"/> 
      <max value="0"/> 
    </element> 
    <element id="Extension.extension:reference.url">
      <path value="Extension.extension.url"/> 
      <fixedUri value="reference"/> 
    </element> 
    <element id="Extension.extension:reference.value[x]">
      <path value="Extension.extension.value[x]"/> 
      <min value="1"/> 
      <type> 
        <code value="Reference"/> 
      </type> 
    </element> 
    <element id="Extension.extension:path">
      <path value="Extension.extension"/> 
      <sliceName value="path"/> 
      <short value="Element containing text."/> 
      <definition value="Corresponds to the element within the resource containing the text."/> 
      <comment value="Follows the FHIRPath expression syntax used for OperationOutcome. If not present, then
       the resource must either be a Binary or a DocumentReference (with a single content element)
       and the content is the text represented by the instance or the attachment.  If the DocumentReference
       has more than one 'content', then this path element SHALL be present to distinguish which
       repetition the derivation occurred from."/> 
      <min value="0"/> 
      <max value="1"/> 
    </element> 
    <element id="Extension.extension:path.extension">
      <path value="Extension.extension.extension"/> 
      <max value="0"/> 
    </element> 
    <element id="Extension.extension:path.url">
      <path value="Extension.extension.url"/> 
      <fixedUri value="path"/> 
    </element> 
    <element id="Extension.extension:path.value[x]">
      <path value="Extension.extension.value[x]"/> 
      <min value="1"/> 
      <type> 
        <code value="string"/> 
      </type> 
    </element> 
    <element id="Extension.extension:offset">
      <path value="Extension.extension"/> 
      <sliceName value="offset"/> 
      <short value="Starting position."/> 
      <definition value="Indicates the starting position (as a count of characters) within the text where the relevant
       derivation began."/> 
      <min value="0"/> 
      <max value="1"/> 
      <meaningWhenMissing value="If not specified, the location at which derivation started is unknown."/> 
    </element> 
    <element id="Extension.extension:offset.extension">
      <path value="Extension.extension.extension"/> 
      <max value="0"/> 
    </element> 
    <element id="Extension.extension:offset.url">
      <path value="Extension.extension.url"/> 
      <fixedUri value="offset"/> 
    </element> 
    <element id="Extension.extension:offset.value[x]">
      <path value="Extension.extension.value[x]"/> 
      <min value="1"/> 
      <type> 
        <code value="integer"/> 
      </type> 
    </element> 
    <element id="Extension.extension:length">
      <path value="Extension.extension"/> 
      <sliceName value="length"/> 
      <short value="Number of characters."/> 
      <definition value="Indicates the number of characters following the start position/beginning of the document
       that was used as part of the derivation process."/> 
      <min value="0"/> 
      <max value="1"/> 
      <meaningWhenMissing value="If not specified, the location at which derivation ended is unknown."/> 
    </element> 
    <element id="Extension.extension:length.extension">
      <path value="Extension.extension.extension"/> 
      <max value="0"/> 
    </element> 
    <element id="Extension.extension:length.url">
      <path value="Extension.extension.url"/> 
      <fixedUri value="length"/> 
    </element> 
    <element id="Extension.extension:length.value[x]">
      <path value="Extension.extension.value[x]"/> 
      <min value="1"/> 
      <type> 
        <code value="integer"/> 
      </type> 
    </element> 
    <element id="Extension.url">
      <path value="Extension.url"/> 
      <fixedUri value="http://hl7.org/fhir/StructureDefinition/derivation-reference"/> 
    </element> 
    <element id="Extension.value[x]">
      <path value="Extension.value[x]"/> 
      <max value="0"/> 
    </element> 
  </differential> 
</StructureDefinition>
Usage note: every effort has been made to ensure that the examples are correct and useful, but they are not a normative part of the specification.