Structured Data Capture
4.0.0-ballot - STU 4 ballot International flag

This page is part of the Structured Data Capture FHIR IG (v4.0.0-ballot: STU 4 Ballot 1) based on FHIR (HL7® FHIR® Standard) R4. The current version which supersedes this version is 3.0.0. For a full list of available versions, see the Directory of published versions

Extension: EnableWhenExpressionExtension - JSON Profile

Page standards status: Trial-use Maturity Level: 4

JSON representation of the sdc-questionnaire-enableWhenExpression extension.

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{
  "resourceType" : "StructureDefinition",
  "id" : "sdc-questionnaire-enableWhenExpression",
  "text" : {
    "status" : "extensions",
    "div" : "<div xmlns=\"http://www.w3.org/1999/xhtml\"><p class=\"res-header-id\"><b>Generated Narrative: StructureDefinition sdc-questionnaire-enableWhenExpression</b></p><a name=\"sdc-questionnaire-enableWhenExpression\"> </a><a name=\"hcsdc-questionnaire-enableWhenExpression\"> </a><a name=\"sdc-questionnaire-enableWhenExpression-en-US\"> </a><table border=\"0\" cellpadding=\"0\" cellspacing=\"0\" style=\"border: 0px #F0F0F0 solid; font-size: 11px; font-family: verdana; vertical-align: top;\"><tr style=\"border: 1px #F0F0F0 solid; font-size: 11px; font-family: verdana; vertical-align: top\"><th style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><a href=\"https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views\" title=\"The logical name of the element\">Name</a></th><th style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><a href=\"https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views\" title=\"Information about the use of the element\">Flags</a></th><th style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><a href=\"https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views\" title=\"Minimum and Maximum # of times the element can appear in the instance\">Card.</a></th><th style=\"width: 100px\" class=\"hierarchy\"><a href=\"https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views\" title=\"Reference to the type of the element\">Type</a></th><th style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><a href=\"https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views\" title=\"Additional information about the element\">Description &amp; Constraints</a><span style=\"float: right\"><a href=\"https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views\" title=\"Legend for this format\"><img src=\"data:image/png;base64,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\" alt=\"doco\" style=\"background-color: inherit\"/></a></span></th></tr><tr style=\"border: 0px #F0F0F0 solid; padding:0px; vertical-align: top; background-color: white\"><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; white-space: nowrap; background-image: url(tbl_bck1.png)\" class=\"hierarchy\"><img src=\"tbl_spacer.png\" alt=\".\" style=\"background-color: inherit\" class=\"hierarchy\"/><img src=\"icon_element.gif\" alt=\".\" style=\"background-color: white; background-color: inherit\" title=\"Element\" class=\"hierarchy\"/> <a href=\"StructureDefinition-sdc-questionnaire-enableWhenExpression-definitions.html#Extension\" title=\"An expression that returns a boolean value for whether to enable the item.\">Extension</a><a name=\"Extension\"> </a></td><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"/><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><span style=\"opacity: 0.5\">0</span>..1</td><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><a href=\"http://hl7.org/fhir/R4/extensibility.html#Extension\">Extension</a></td><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\">Expression for when to enable the item</td></tr>\r\n<tr style=\"border: 0px #F0F0F0 solid; padding:0px; vertical-align: top; background-color: #F7F7F7\"><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; white-space: nowrap; background-image: url(tbl_bck10.png)\" class=\"hierarchy\"><img src=\"tbl_spacer.png\" alt=\".\" style=\"background-color: inherit\" class=\"hierarchy\"/><img src=\"tbl_vjoin.png\" alt=\".\" style=\"background-color: inherit\" class=\"hierarchy\"/><img src=\"icon_extension_simple.png\" alt=\".\" style=\"background-color: #F7F7F7; background-color: inherit\" title=\"Simple Extension\" class=\"hierarchy\"/> <span style=\"text-decoration:line-through\">extension</span><a name=\"Extension.extension\"> </a></td><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"/><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><span style=\"text-decoration:line-through\"/><span style=\"text-decoration:line-through\">0</span><span style=\"text-decoration:line-through\">..</span><span style=\"text-decoration:line-through\">0</span></td><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"/><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"/></tr>\r\n<tr style=\"border: 0px #F0F0F0 solid; padding:0px; vertical-align: top; background-color: white\"><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; white-space: nowrap; background-image: url(tbl_bck10.png)\" class=\"hierarchy\"><img src=\"tbl_spacer.png\" alt=\".\" style=\"background-color: inherit\" class=\"hierarchy\"/><img src=\"tbl_vjoin.png\" alt=\".\" style=\"background-color: inherit\" class=\"hierarchy\"/><img src=\"icon_element.gif\" alt=\".\" style=\"background-color: white; background-color: inherit\" title=\"Element\" class=\"hierarchy\"/> <a href=\"StructureDefinition-sdc-questionnaire-enableWhenExpression-definitions.html#Extension.url\">url</a><a name=\"Extension.url\"> </a></td><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"/><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><span style=\"opacity: 0.5\">1</span><span style=\"opacity: 0.5\">..</span><span style=\"opacity: 0.5\">1</span></td><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><a style=\"opacity: 0.5\" href=\"http://hl7.org/fhir/R4/datatypes.html#uri\">uri</a></td><td style=\"vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><span style=\"color: darkgreen\">&quot;http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression&quot;</span></td></tr>\r\n<tr style=\"border: 0px #F0F0F0 solid; padding:0px; vertical-align: top; background-color: #F7F7F7\"><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; white-space: nowrap; background-image: url(tbl_bck00.png)\" class=\"hierarchy\"><img src=\"tbl_spacer.png\" alt=\".\" style=\"background-color: inherit\" class=\"hierarchy\"/><img src=\"tbl_vjoin_end.png\" alt=\".\" style=\"background-color: inherit\" class=\"hierarchy\"/><img src=\"icon_datatype.gif\" alt=\".\" style=\"background-color: #F7F7F7; background-color: inherit\" title=\"Data Type\" class=\"hierarchy\"/> <a href=\"StructureDefinition-sdc-questionnaire-enableWhenExpression-definitions.html#Extension.value[x]\">value[x]</a><a name=\"Extension.value_x_\"> </a></td><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><a style=\"padding-left: 3px; padding-right: 3px; border: 1px maroon solid; font-weight: bold; color: #301212; background-color: #fdf4f4;\" href=\"http://hl7.org/fhir/R4/conformance-rules.html#constraints\" title=\"This element has or is affected by constraints ( sdc-inv1 )\">C</a></td><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><span style=\"opacity: 0.5\">0</span><span style=\"opacity: 0.5\">..</span><span style=\"opacity: 0.5\">1</span></td><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><a href=\"http://hl7.org/fhir/R4/datatypes.html#Expression\">Expression</a></td><td style=\"vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px\" class=\"hierarchy\"><span style=\"opacity: 0.5\">Value of extension</span><br/><span style=\"font-weight:bold\">sdc-inv1: </span>FHIR query language not allowed.</td></tr>\r\n<tr><td colspan=\"5\" class=\"hierarchy\"><br/><a href=\"https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views\" title=\"Legend for this format\"><img src=\"data:image/png;base64,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\" alt=\"doco\" style=\"background-color: inherit\"/> Documentation for this format</a></td></tr></table></div>"
  },
  "extension" : [
    {
      "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
      "valueCode" : "fhir"
    },
    {
      "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm",
      "valueInteger" : 4,
      "_valueInteger" : {
        "extension" : [
          {
            "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-conformance-derivedFrom",
            "valueCanonical" : "http://hl7.org/fhir/uv/sdc/ImplementationGuide/hl7.fhir.uv.sdc"
          }
        ]
      }
    },
    {
      "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status",
      "valueCode" : "trial-use",
      "_valueCode" : {
        "extension" : [
          {
            "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-conformance-derivedFrom",
            "valueCanonical" : "http://hl7.org/fhir/uv/sdc/ImplementationGuide/hl7.fhir.uv.sdc"
          }
        ]
      }
    }
  ],
  "url" : "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression",
  "identifier" : [
    {
      "system" : "urn:ietf:rfc:3986",
      "value" : "urn:oid:2.16.840.1.113883.4.642.40.17.42.22"
    }
  ],
  "version" : "4.0.0-ballot",
  "name" : "EnableWhenExpressionExtension",
  "title" : "Enable when expression",
  "status" : "active",
  "experimental" : false,
  "date" : "2024-12-17T01:55:34+00:00",
  "publisher" : "HL7 International / FHIR Infrastructure",
  "contact" : [
    {
      "name" : "HL7 International / FHIR Infrastructure",
      "telecom" : [
        {
          "system" : "url",
          "value" : "http://www.hl7.org/Special/committees/fiwg"
        }
      ]
    },
    {
      "telecom" : [
        {
          "system" : "url",
          "value" : "http://www.hl7.org/Special/committees/fiwg"
        }
      ]
    }
  ],
  "description" : "An expression that returns a boolean value for whether to enable the item. If the expression does not resolve to a boolean, it is considered an error in the design of the Questionnaire.  Form renderer behavior is undefined.  Some tools may attempt to force the value to be a boolean (e.g. is it a non-empty collection, non-null, non-zero - if so, then true).  Systems SHOULD present a warning to the user if a non-boolean valued expression result does not trigger an all-out error.",
  "jurisdiction" : [
    {
      "coding" : [
        {
          "system" : "http://unstats.un.org/unsd/methods/m49/m49.htm",
          "code" : "001",
          "display" : "World"
        }
      ]
    }
  ],
  "fhirVersion" : "4.0.1",
  "mapping" : [
    {
      "identity" : "rim",
      "uri" : "http://hl7.org/v3",
      "name" : "RIM Mapping"
    }
  ],
  "kind" : "complex-type",
  "abstract" : false,
  "context" : [
    {
      "type" : "element",
      "expression" : "Questionnaire.item"
    },
    {
      "type" : "element",
      "expression" : "ElementDefinition"
    }
  ],
  "type" : "Extension",
  "baseDefinition" : "http://hl7.org/fhir/StructureDefinition/Extension",
  "derivation" : "constraint",
  "snapshot" : {
    "element" : [
      {
        "id" : "Extension",
        "path" : "Extension",
        "short" : "Expression for when to enable the item",
        "definition" : "An expression that returns a boolean value for whether to enable the item.",
        "comment" : "This is only permitted when the containing item does NOT have any enableWhen elements.\r\n\r\nIf the expression involves comparisons between elements that have different precisions but are otherwise equal, FHIRPath will resolve the expression to an empty set, which will in turn evaluate to false (meaning the item won't be enabled).  If this is not the desired behavior, the author should add a `.allTrue()` to the end of the expression, which will result in an indeterminate outcome because of precision differences being handled as 'true' and the item being enabled.  Questionnaires SHOULD be designed to take into account challenges around varying precision to minimize non-deterministic situations by setting constraints around expected precision, etc.\r\n\r\nIf the expression evaluates to something other than a boolean true or false, the Form Filler SHOULD still display the form, and if it does so, SHOULD treat the element as 'enabled' and display a warning to the user that the questionnaire logic was faulty and it's possible that the item shouldn't be enabled.",
        "min" : 0,
        "max" : "1",
        "base" : {
          "path" : "Extension",
          "min" : 0,
          "max" : "*"
        },
        "condition" : [
          "ele-1"
        ],
        "constraint" : [
          {
            "key" : "ele-1",
            "severity" : "error",
            "human" : "All FHIR elements must have a @value or children",
            "expression" : "hasValue() or (children().count() > id.count())",
            "xpath" : "@value|f:*|h:div",
            "source" : "http://hl7.org/fhir/StructureDefinition/Element"
          },
          {
            "key" : "ext-1",
            "severity" : "error",
            "human" : "Must have either extensions or value[x], not both",
            "expression" : "extension.exists() != value.exists()",
            "xpath" : "exists(f:extension)!=exists(f:*[starts-with(local-name(.), 'value')])",
            "source" : "http://hl7.org/fhir/StructureDefinition/Extension"
          }
        ],
        "isModifier" : false
      },
      {
        "id" : "Extension.id",
        "path" : "Extension.id",
        "representation" : [
          "xmlAttr"
        ],
        "short" : "Unique id for inter-element referencing",
        "definition" : "Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.",
        "min" : 0,
        "max" : "1",
        "base" : {
          "path" : "Element.id",
          "min" : 0,
          "max" : "1"
        },
        "type" : [
          {
            "extension" : [
              {
                "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type",
                "valueUrl" : "string"
              }
            ],
            "code" : "http://hl7.org/fhirpath/System.String"
          }
        ],
        "isModifier" : false,
        "isSummary" : false,
        "mapping" : [
          {
            "identity" : "rim",
            "map" : "n/a"
          }
        ]
      },
      {
        "id" : "Extension.extension",
        "path" : "Extension.extension",
        "slicing" : {
          "discriminator" : [
            {
              "type" : "value",
              "path" : "url"
            }
          ],
          "description" : "Extensions are always sliced by (at least) url",
          "rules" : "open"
        },
        "short" : "Extension",
        "definition" : "An Extension",
        "min" : 0,
        "max" : "0",
        "base" : {
          "path" : "Element.extension",
          "min" : 0,
          "max" : "*"
        },
        "type" : [
          {
            "code" : "Extension"
          }
        ],
        "constraint" : [
          {
            "key" : "ele-1",
            "severity" : "error",
            "human" : "All FHIR elements must have a @value or children",
            "expression" : "hasValue() or (children().count() > id.count())",
            "xpath" : "@value|f:*|h:div",
            "source" : "http://hl7.org/fhir/StructureDefinition/Element"
          },
          {
            "key" : "ext-1",
            "severity" : "error",
            "human" : "Must have either extensions or value[x], not both",
            "expression" : "extension.exists() != value.exists()",
            "xpath" : "exists(f:extension)!=exists(f:*[starts-with(local-name(.), \"value\")])",
            "source" : "http://hl7.org/fhir/StructureDefinition/Extension"
          }
        ],
        "isModifier" : false,
        "isSummary" : false
      },
      {
        "id" : "Extension.url",
        "path" : "Extension.url",
        "representation" : [
          "xmlAttr"
        ],
        "short" : "identifies the meaning of the extension",
        "definition" : "Source of the definition for the extension code - a logical name or a URL.",
        "comment" : "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" : 1,
        "max" : "1",
        "base" : {
          "path" : "Extension.url",
          "min" : 1,
          "max" : "1"
        },
        "type" : [
          {
            "extension" : [
              {
                "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type",
                "valueUrl" : "uri"
              }
            ],
            "code" : "http://hl7.org/fhirpath/System.String"
          }
        ],
        "fixedUri" : "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression",
        "isModifier" : false,
        "isSummary" : false,
        "mapping" : [
          {
            "identity" : "rim",
            "map" : "N/A"
          }
        ]
      },
      {
        "id" : "Extension.value[x]",
        "path" : "Extension.value[x]",
        "short" : "Value of extension",
        "definition" : "Value of extension - must be one of a constrained set of the data types (see [Extensibility](http://hl7.org/fhir/R4/extensibility.html) for a list).",
        "min" : 0,
        "max" : "1",
        "base" : {
          "path" : "Extension.value[x]",
          "min" : 0,
          "max" : "1"
        },
        "type" : [
          {
            "code" : "Expression"
          }
        ],
        "constraint" : [
          {
            "key" : "ele-1",
            "severity" : "error",
            "human" : "All FHIR elements must have a @value or children",
            "expression" : "hasValue() or (children().count() > id.count())",
            "xpath" : "@value|f:*|h:div",
            "source" : "http://hl7.org/fhir/StructureDefinition/Element"
          },
          {
            "key" : "sdc-inv1",
            "severity" : "error",
            "human" : "FHIR query language not allowed.",
            "expression" : "language!='application/x-fhir-query'",
            "xpath" : "not(f:language/@value='application/x-fhir-query')",
            "source" : "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression"
          }
        ],
        "isModifier" : false,
        "isSummary" : false,
        "mapping" : [
          {
            "identity" : "rim",
            "map" : "N/A"
          }
        ]
      }
    ]
  },
  "differential" : {
    "element" : [
      {
        "id" : "Extension",
        "path" : "Extension",
        "short" : "Expression for when to enable the item",
        "definition" : "An expression that returns a boolean value for whether to enable the item.",
        "comment" : "This is only permitted when the containing item does NOT have any enableWhen elements.\r\n\r\nIf the expression involves comparisons between elements that have different precisions but are otherwise equal, FHIRPath will resolve the expression to an empty set, which will in turn evaluate to false (meaning the item won't be enabled).  If this is not the desired behavior, the author should add a `.allTrue()` to the end of the expression, which will result in an indeterminate outcome because of precision differences being handled as 'true' and the item being enabled.  Questionnaires SHOULD be designed to take into account challenges around varying precision to minimize non-deterministic situations by setting constraints around expected precision, etc.\r\n\r\nIf the expression evaluates to something other than a boolean true or false, the Form Filler SHOULD still display the form, and if it does so, SHOULD treat the element as 'enabled' and display a warning to the user that the questionnaire logic was faulty and it's possible that the item shouldn't be enabled.",
        "max" : "1"
      },
      {
        "id" : "Extension.extension",
        "path" : "Extension.extension",
        "max" : "0"
      },
      {
        "id" : "Extension.url",
        "path" : "Extension.url",
        "fixedUri" : "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression"
      },
      {
        "id" : "Extension.value[x]",
        "path" : "Extension.value[x]",
        "type" : [
          {
            "code" : "Expression"
          }
        ],
        "constraint" : [
          {
            "key" : "sdc-inv1",
            "severity" : "error",
            "human" : "FHIR query language not allowed.",
            "expression" : "language!='application/x-fhir-query'",
            "xpath" : "not(f:language/@value='application/x-fhir-query')",
            "source" : "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression"
          }
        ]
      }
    ]
  }
}