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Null, Empty and Invalid Values

Null (also referred to as Present But Null), Empty and Invalid values are important concepts in the HL7 world. They are defined as follows:

• Null - A null value is sent to a receiving application when the sender wants to inform the receiver that it has no data for a specific field, subfield, or sub-subfield. Null is expressed using two double quotes. For example:

|""|

• Empty - An empty value is sent to a receiving application when the sender wants to inform the receiver that there is no explicit data for a specific field, subfield, or sub-subfield. Empty is expressed using no value. For example:

||

• Invalid - An invalid value is when incorrect data is inserted in a field, subfield, or sub-subfield. For example, when "XYZ" is inserted in a Date Time field.

|XYZ|