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|

Iguana 4.0 and later versions treat null, empty and invalid values differently (i.e. inserts/updates in your database), depending on the selected parser version in the VMD file, the input data, and the data type.

	Multiple parser versions are supported in Iguana 4.0 and later only. Earlier versions of Iguana do not recognize different parser versions.

The following tables summarize the differences when using the 5.0 (recommended parser) and 4.5 parser engines:

4.5 Parser Engine

	Selecting the Parser Engine To change the Parser Engine you want to use, click Options > Misc in Chameleon's main menu.

5.0 Parser Engine (Recommended Parser Engine)

	Selecting the Parser Engine The 5.0 Parser Engine is only available in Chameleon versions 5.0 and later. To change the Parser Engine you want to use, click Options > Misc in Chameleon's main menu.   Key Fields If a key field is NULL or Present But Null and one or more columns are empty, an error will occur.