This is the Continuous Integration Build of FHIR (will be incorrect/inconsistent at times).
See the Directory of published versions
FHIR Infrastructure Work Group | Maturity Level: Normative | Standards Status: Normative |
This page documents how the content of the resources are described. In actual exchange, resources can be represented in the following formats: XML, JSON and Turtle. A UML Based Object-Oriented Definition is also provided.
The resources are described in several different ways:
In addition to this descriptive syntax, other definitional forms are available, including W3C schema, Schematron, JSON Schema, and the StructureDefinition syntax defined internally.
The Logical View shows the resources as a tree structure with the following columns:
Column | Content |
Name | The name of the element in the resource (manifests as XML element name or JSON or RDF property name). Some names finish with [x] - the meaning of this is discussed below. In addition, this column contains an icon that denotes the underlying type of the content. The icons are described below |
Flags | A set of information about the element that impacts how implementers handle them. The flags are described below |
Card. | Cardinality: the lower and upper bounds on how many times this element is allowed to appear in the resource |
Type | The type of the element (hyperlinked to the definition of the type). Note that the type of the element has one of two meanings, depending on whether the element has defined children. If the element has children, then the element has an anonymous type that specializes the given type. If the element has no children, then the element has properties and children as specified by the nominated type |
Description & Constraints | A description of the element, and details about constraints that are applied to it. Particularly, for coded elements, information about which codes can be used. The description comes from ElementDefinition.short |
Here's an example:
Name | Flags | Card. | Type | Description & Constraints |
---|---|---|---|---|
Resource Name | Base Type | Definition | ||
nameA | Σ | 1..1 | TypeA | description of content |
nameB[x] | ?! Σ | 0..1 | description SHALL at least have a value |
|
nameBType1 | 0..1 | typeB | ||
nameBType2 | I | 0..1 | typeC | |
nameC | 1..* | BackboneElement | Definition | |
nameD | 1..1 | TypeD | Relevant Records |
Key to Type Icons
value
attribute/property. These are also known as primitive types. All primitive type names start with a lower case letterKey to Flags
?!
: This element is a modifying element - see Modifier ElementsS
: This element is an element that has implementation obligations - see Implementation ObligationsΣ
: This element is an element that is part of the summary set - see Summary SearchesI
: This element defines or is affected by constraints - see ConstraintsT
: This element is a candidate for carrying translations - see Multi-language support«A»
: This Type is an Abstract Type«I»
: This Resource is an Interface DefinitionNotes:
value
attribute/property to contain the actual value of the elementvalue
attribute/property can never be empty. Either it is absent, or it is present with at least one character of non-whitespace contentid
attribute to serve as the target of an internal reference. The id
attribute is not shown in this format. Extensions are not always shown, but may appear except where the flag NE
appearsThe datatype for a particular element is typically expressed as the name of the specified type with a hyperlink to its definition. However, there are two exceptions:
In profiles, references to types may be profiled - i.e. Instances of the element must comply with a specified profile or one of a list of profiles. The canonical URLs of any applicable profiles are listed inside {}.
Where an element can have a choice of datatypes, or is a Reference these are
represented by showing the common type (Reference
or Type
), and then showing the applicable datatype names or
resource types in a stereotype, separated by the |
character.
A few elements have a choice of more than one datatype for their content. All such elements have a name that
takes the form nnn[x]
. The "nnn" part of the name is constant, and the "[x]" is replaced with the title-cased
name of the type that is actually used. The table view shows each of these names explicitly.
Elements that have a choice of datatype cannot repeat - they must have a maximum cardinality of 1. When constructing an instance of an element with a choice of types, the authoring system must create a single element with a datatype chosen from among the list of permitted datatypes.
Note: In object-oriented implementations, this is naturally represented as a polymorphic property (see Object Representation of FHIR). However this is not necessary and the correct implementation varies according to the particular features of the language. In XML schema, these become an xs:choice of element. To help with code generation, a list of choice elements is published.