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2.6.4 Optionality

Whether the field is required, optional, or conditional in a segment. The designations are:

R

-

required

O

-

optional

C

-

conditional on the trigger event or on some other field(s)

X

-

not used with this trigger event

B

-

left in for backward compatibility with previous versions of HL7

Note: For Versions 2.3 and higher: the optionality of fields should be explicitly documented in the segment field definitions that follow each segment definition table; if the optionality of fields within a segment changes depending on the trigger event, that optionality should also be explicitly documented.

Note: For fields defined by HL7 data types containing multiple components or subcomponents, the optionality of a given component or sub-component must be specified in the detailed field definitions that follow the formal segment attribute tables. (See also Sections 2.7, "MESSAGE DELIMITERS," 2.8, "Data types," and 2.10, "Message construction rules").

In the segment attribute tables this information is in a column labeled OPT.

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