{
  "resourceType": "StructureDefinition",
  "id": "nexus-allergen-class-extension",
  "url": "https://fhir.apps.health/StructureDefinition/nexus-allergen-class-extension",
  "name": "NexusAllergenClass",
  "title": "Allergen Class Extension",
  "status": "draft",
  "experimental": false,
  "description": "What kind of thing the recorded allergen is: a single drug, a drug class, a food, an environmental\nsubstance or a vaccine.\n\n**It determines `category`, and says the thing `category` cannot.** Every value here maps onto\nexactly one of R4's four `AllergyIntolerance.category` values, and two of them -- `drug` and\n`class` -- map onto the same one. That collision is the point: a reaction recorded against one\nmedicinal substance and a reaction recorded against a whole family of them are both `medication`,\nand a cross-sensitivity check against a new prescription needs to know which it is reading.\n\n**It is a fact about the record, not a translation of the substance.**\n[`AllergyIntolerance.code`](StructureDefinition-nexus-emr-core-allergyintolerance.md) carries WHAT\nthe patient reacted to, and every coding in it says that same thing in a different vocabulary. This\nsays WHAT KIND, which is a different and coarser statement, so it rides an element of its own.\n\n**At most one per record.** A record whose substance carries several codings still describes one\nallergen and therefore one class.\n\n**MIGRATION.** Write this extension. Records written before it exists carry the class as an\nadditional coding inside `AllergyIntolerance.code.coding`, under the same code system; that\ncarriage is not part of this specification and is not produced going forward. A reader of older\nrecords has to read it from where it was written, and must not mistake it for a translation of the\nsubstance while doing so. Moving the existing data is outstanding work and is not described here.",
  "fhirVersion": "4.0.1",
  "mapping": [
    {
      "identity": "rim",
      "uri": "http://hl7.org/v3",
      "name": "RIM Mapping"
    }
  ],
  "kind": "complex-type",
  "abstract": false,
  "context": [
    {
      "type": "element",
      "expression": "AllergyIntolerance"
    }
  ],
  "type": "Extension",
  "baseDefinition": "http://hl7.org/fhir/StructureDefinition/Extension",
  "derivation": "constraint",
  "snapshot": {
    "element": [
      {
        "id": "Extension",
        "path": "Extension",
        "short": "Allergen Class Extension",
        "definition": "What kind of thing the recorded allergen is: a single drug, a drug class, a food, an environmental\nsubstance or a vaccine.\n\n**It determines `category`, and says the thing `category` cannot.** Every value here maps onto\nexactly one of R4's four `AllergyIntolerance.category` values, and two of them -- `drug` and\n`class` -- map onto the same one. That collision is the point: a reaction recorded against one\nmedicinal substance and a reaction recorded against a whole family of them are both `medication`,\nand a cross-sensitivity check against a new prescription needs to know which it is reading.\n\n**It is a fact about the record, not a translation of the substance.**\n[`AllergyIntolerance.code`](StructureDefinition-nexus-emr-core-allergyintolerance.md) carries WHAT\nthe patient reacted to, and every coding in it says that same thing in a different vocabulary. This\nsays WHAT KIND, which is a different and coarser statement, so it rides an element of its own.\n\n**At most one per record.** A record whose substance carries several codings still describes one\nallergen and therefore one class.\n\n**MIGRATION.** Write this extension. Records written before it exists carry the class as an\nadditional coding inside `AllergyIntolerance.code.coding`, under the same code system; that\ncarriage is not part of this specification and is not produced going forward. A reader of older\nrecords has to read it from where it was written, and must not mistake it for a translation of the\nsubstance while doing so. Moving the existing data is outstanding work and is not described here.",
        "min": 0,
        "max": "*",
        "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')])"
          }
        ],
        "isModifier": false,
        "mapping": [
          {
            "identity": "rim",
            "map": "n/a"
          },
          {
            "identity": "rim",
            "map": "N/A"
          }
        ]
      },
      {
        "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": [
          {
            "code": "http://hl7.org/fhirpath/System.String",
            "extension": [
              {
                "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type",
                "valueUrl": "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": "Additional content defined by implementations",
        "definition": "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": "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": [
          "extensions",
          "user content"
        ],
        "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,
        "mapping": [
          {
            "identity": "rim",
            "map": "n/a"
          }
        ]
      },
      {
        "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": [
          {
            "code": "http://hl7.org/fhirpath/System.String",
            "extension": [
              {
                "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type",
                "valueUrl": "uri"
              }
            ]
          }
        ],
        "fixedUri": "https://fhir.apps.health/StructureDefinition/nexus-allergen-class-extension",
        "isModifier": false,
        "isSummary": false,
        "mapping": [
          {
            "identity": "rim",
            "map": "N/A"
          }
        ]
      },
      {
        "id": "Extension.value[x]",
        "path": "Extension.value[x]",
        "short": "What kind of thing the allergen is",
        "definition": "The allergen's kind, from the allergen class vocabulary. A required binding: the set is closed and complete -- it is the five kinds this estate's allergen picker assigns -- so a value outside it is not an extension of the concept but a different one, and belongs in a different element.",
        "min": 1,
        "max": "1",
        "base": {
          "path": "Extension.value[x]",
          "min": 0,
          "max": "1"
        },
        "type": [
          {
            "code": "Coding"
          }
        ],
        "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,
        "binding": {
          "strength": "required",
          "valueSet": "https://fhir.apps.health/ValueSet/nexus-allergen-class"
        },
        "mapping": [
          {
            "identity": "rim",
            "map": "N/A"
          }
        ]
      }
    ]
  },
  "differential": {
    "element": [
      {
        "id": "Extension",
        "path": "Extension",
        "short": "Allergen Class Extension",
        "definition": "What kind of thing the recorded allergen is: a single drug, a drug class, a food, an environmental\nsubstance or a vaccine.\n\n**It determines `category`, and says the thing `category` cannot.** Every value here maps onto\nexactly one of R4's four `AllergyIntolerance.category` values, and two of them -- `drug` and\n`class` -- map onto the same one. That collision is the point: a reaction recorded against one\nmedicinal substance and a reaction recorded against a whole family of them are both `medication`,\nand a cross-sensitivity check against a new prescription needs to know which it is reading.\n\n**It is a fact about the record, not a translation of the substance.**\n[`AllergyIntolerance.code`](StructureDefinition-nexus-emr-core-allergyintolerance.md) carries WHAT\nthe patient reacted to, and every coding in it says that same thing in a different vocabulary. This\nsays WHAT KIND, which is a different and coarser statement, so it rides an element of its own.\n\n**At most one per record.** A record whose substance carries several codings still describes one\nallergen and therefore one class.\n\n**MIGRATION.** Write this extension. Records written before it exists carry the class as an\nadditional coding inside `AllergyIntolerance.code.coding`, under the same code system; that\ncarriage is not part of this specification and is not produced going forward. A reader of older\nrecords has to read it from where it was written, and must not mistake it for a translation of the\nsubstance while doing so. Moving the existing data is outstanding work and is not described here."
      },
      {
        "id": "Extension.extension",
        "path": "Extension.extension",
        "max": "0"
      },
      {
        "id": "Extension.url",
        "path": "Extension.url",
        "fixedUri": "https://fhir.apps.health/StructureDefinition/nexus-allergen-class-extension"
      },
      {
        "id": "Extension.value[x]",
        "path": "Extension.value[x]",
        "short": "What kind of thing the allergen is",
        "definition": "The allergen's kind, from the allergen class vocabulary. A required binding: the set is closed and complete -- it is the five kinds this estate's allergen picker assigns -- so a value outside it is not an extension of the concept but a different one, and belongs in a different element.",
        "min": 1,
        "type": [
          {
            "code": "Coding"
          }
        ],
        "binding": {
          "strength": "required",
          "valueSet": "https://fhir.apps.health/ValueSet/nexus-allergen-class"
        }
      }
    ]
  }
}