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EI - entity identifier

HL7 Component Table - EI - entity identifier
Seq# Description Implement Flags Cardinality Length C.LEN Vocabulary Data Type
1 Entity Identifier = [0..1] 199 ST
2 Namespace ID = [0..1]  20 0363 IS

Universal ID MAY
C =
199 ST
4 Universal ID Type MAY
[1..6]     0301 ID

Components: <Entity Identifier (ST)> & <Namespace ID (IS)> & <Universal ID (ST)> & <Universal ID Type (ID)>

Definition: The entity identifier defines a given entity within a specified series of identifiers.

The EI is appropriate for, but not limited to, machine or software generated identifiers. The generated identifier goes in the first component. The remaining components, 2 through 4, are known as the assigning authority; they identify the machine/system responsible for generating the identifier in component 1.

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.A.33, "HD - hierarchic designator". Hierarchic designators (HD) are unique across a given HL7 implementation.

EI-1: Entity Identifier (ST)

Definition: The first component, <entity identifier>, is usually defined to be unique within the series of identifiers created by the <assigning authority>, defined by a hierarchic designator, represented by components 2 through 4. See Section 2.A.33, "HD - hierarchic designator".

EI-2: Namespace ID (IS)

Definition: See Section 2.A.33.1, "Namespace ID (IS)" for definition. The component intentionally remains associated with the IS data type in v 2.7.

The assigning authority is a unique identifier of the system (or organization or agency or department) that creates the data. Refer to User-defined Table 0363 – Assigning Authority for suggested values.

Note: When the HD is used as a part of another data type, in this case as part of the EI data type, this table may be re-defined (given a different user-defined table number and name) by the technical committee responsible for that segment.

By site agreement, implementers may continue to use User-defined Table 0300 – Namespace ID for the first component

EI-3: Universal ID (ST)

Definition: See Section 2.A.33.2, "Universal ID (ST)" for definition.

EI-4: Universal ID Type (ID)

Definition: Refer to HL7 Table 0301 - Universal ID Type for valid values. See Section 2.A.33.3, "Universal ID Type (ID)," for definition.