The entity identifier defines a given entity within a specified series of identifiers.
The specified series, the assigning authority, is defined by components 2 through 4. The assigning authority is of the hierarchic designator (HD) data type, but it is defined as three separate components in the EI data type, rather than as a single component as would normally be the case. This is in order to maintain backward compatibility with the EI's use as a component in several existing data fields. Otherwise, the components 2 through 4 are as defined in Section 2.8.20, "HD - hierarchic designator." Hierarchic designators (HD) are unique across a given HL7 implementation.
4
| Comp# | Comp TBL | FHIR | ||||||
|---|---|---|---|---|---|---|---|---|
| 1 | 303 | O | - | - | EI.1 | entity identifier | ||
| 2 | 441 | O | EI.2 | namespace ID | ||||
| 3 | 442 | O | - | - | EI.3 | universal ID | ||
| 4 | 343 | O | - | EI.4 | universal ID type |
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2