This extension associates a structure definition with a data dictionary - a collection of data elements that any instance of data that conforms to the structure definition must also conform to. The value of the extension is a uri the defines a query that identifies the collection of relevant data elements

This extension can be used on any structure definition that is a constraint on the resource types Observation and Questionnaire. THe profile specifies which elements are mandatory etc., but any elements in a resource that conforms to the structure definition must also conform to one of the defined data elements.

For Observation: * Observation.code must be associated with a matching Data Element by DataElement.code. * The structure definition should bind Observation.code to a value set that has the same codes as the collection of data elements (though it can be narrower) * the unit and the quantity value should conform to the rules laid down in the matching Data Element

For Questionnaire: * todo.

The query can select a set of data element resources, or identify a bundle that is a collection of data elements.

unique id for the element within a resource (for internal references).

An Extension

Source of the definition for the extension code - a logical name or a URL.

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 should be version specific. This will ideally be the URI for the Resource Profile defining the extension, with the code for the extension after a #.

Value of extension - may be a resource or one of a constrained set of the data types (see Extensibility in the spec for list).