A code representing the focus of an observation when the focus is not the patient of record. In other words, the focus of the observation is different from Observation.subject. An example use case would be using the Observation resource to capture whether the mother is trained to change her child's tracheostomy tube. In this example, the child is the patient of record and the mother is focal subject referenced using this extension. Other example focal subjects include spouses, related persons, feti, or donors.

Use Observation.specimen element to describe the specimen. Only used if not implicit in code found in Observation.code.

Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

An Extension

• unordered
• Open
• discriminators: value:url

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 SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).