Variable

{
  "resourceType" : "StructureDefinition",
  "id" : "variable",
  "extension" : [{
    "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
    "valueCode" : "fhir"
  },
  {
    "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm",
    "valueInteger" : 1
  }],
  "url" : "http://hl7.org/fhir/StructureDefinition/variable",
  "version" : "5.0.0-ballot",
  "name" : "Variable",
  "title" : "Variable",
  "status" : "draft",
  "experimental" : false,
  "date" : "2013-12-05",
  "publisher" : "Health Level Seven International (FHIR Infrastructure)",
  "contact" : [{
    "telecom" : [{
      "system" : "url",
      "value" : "http://www.hl7.org/Special/committees/fiwg"
    }]
  }],
  "description" : "Variable specifying a logic to generate a variable for use in subsequent logic.  The name of the variable will be added to FHIRPath's context when processing descendants of the element that contains this extension as well as extensions within the same element.",
  "fhirVersion" : "5.0.0-ballot",
  "mapping" : [{
    "identity" : "rim",
    "uri" : "http://hl7.org/v3",
    "name" : "RIM Mapping"
  }],
  "kind" : "complex-type",
  "abstract" : false,
  "context" : [{
    "type" : "element",
    "expression" : "Questionnaire"
  },
  {
    "type" : "element",
    "expression" : "Questionnaire.item"
  },
  {
    "type" : "element",
    "expression" : "Questionnaire.item.item"
  },
  {
    "type" : "element",
    "expression" : "PlanDefinition"
  },
  {
    "type" : "element",
    "expression" : "PlanDefinition.action"
  },
  {
    "type" : "element",
    "expression" : "PlanDefinition.action.action"
  },
  {
    "type" : "element",
    "expression" : "RequestOrchestration"
  },
  {
    "type" : "element",
    "expression" : "RequestOrchestration.action"
  },
  {
    "type" : "element",
    "expression" : "RequestOrchestration.action.action"
  },
  {
    "type" : "element",
    "expression" : "ActivityDefinition"
  },
  {
    "type" : "element",
    "expression" : "Measure"
  },
  {
    "type" : "element",
    "expression" : "Measure.group"
  },
  {
    "type" : "element",
    "expression" : "Measure.group.population"
  }],
  "type" : "Extension",
  "baseDefinition" : "http://hl7.org/fhir/StructureDefinition/Extension",
  "derivation" : "constraint",
  "snapshot" : {
    "element" : [{
      "id" : "Extension",
      "path" : "Extension",
      "short" : "Variable for processing",
      "definition" : "Variable specifying a logic to generate a variable for use in subsequent logic.  The name of the variable will be added to FHIRPath's context when processing descendants of the element that contains this extension as well as extensions within the same element.",
      "comment" : "Ordering of variable extension declarations is significant as variables declared in one repetition of this extension might be used in subsequent extension repetitions\n\nFor questionnaires, see additional guidance and examples in the [SDC implementation guide](http://build.fhir.org/ig/HL7/sdc/behavior.html#variable).",
      "min" : 0,
      "max" : "*",
      "base" : {
        "path" : "Extension",
        "min" : 0,
        "max" : "*"
      },
      "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"
      },
      {
        "key" : "var-1",
        "severity" : "error",
        "human" : "Variable expressions must have a name",
        "expression" : "value.name.exists()",
        "xpath" : "exists(f:valueExpression/f:name)"
      }],
      "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" : "id"
        }],
        "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/StructureDefinition/variable",
      "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](extensibility.html) for a list).",
      "min" : 1,
      "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"
      }],
      "isModifier" : false,
      "isSummary" : false,
      "mapping" : [{
        "identity" : "rim",
        "map" : "N/A"
      }]
    }]
  },
  "differential" : {
    "element" : [{
      "id" : "Extension",
      "path" : "Extension",
      "short" : "Variable for processing",
      "definition" : "Variable specifying a logic to generate a variable for use in subsequent logic.  The name of the variable will be added to FHIRPath's context when processing descendants of the element that contains this extension as well as extensions within the same element.",
      "comment" : "Ordering of variable extension declarations is significant as variables declared in one repetition of this extension might be used in subsequent extension repetitions\n\nFor questionnaires, see additional guidance and examples in the [SDC implementation guide](http://build.fhir.org/ig/HL7/sdc/behavior.html#variable).",
      "min" : 0,
      "max" : "*",
      "constraint" : [{
        "key" : "var-1",
        "severity" : "error",
        "human" : "Variable expressions must have a name",
        "expression" : "value.name.exists()",
        "xpath" : "exists(f:valueExpression/f:name)"
      }]
    },
    {
      "id" : "Extension.extension",
      "path" : "Extension.extension",
      "max" : "0"
    },
    {
      "id" : "Extension.url",
      "path" : "Extension.url",
      "fixedUri" : "http://hl7.org/fhir/StructureDefinition/variable"
    },
    {
      "id" : "Extension.value[x]",
      "path" : "Extension.value[x]",
      "min" : 1,
      "type" : [{
        "code" : "Expression"
      }]
    }]
  }
}