**Description:**A proper value is applicable, but not known.

Usage Notes: This means the actual value is not known. If the only thing that is unknown is how to properly express the value in the necessary constraints (value set, datatype, etc.), then the OTH or UNC flavor should be used. No properties should be included for a datatype with this property unless:

1. Those properties themselves directly translate to a semantic of "unknown". (E.g. a local code sent as a translation that conveys 'unknown')
2. Those properties further qualify the nature of what is unknown. (E.g. specifying a use code of "H" and a URL prefix of "tel:" to convey that it is the home phone number that is unknown.)

Information was sought but not found (e.g., patient was asked but didn't know)

Information is not available at this time but it is expected that it will be available later.

This information has not been sought (e.g., patient was not asked)

Information is not available at this time (with no expectation regarding whether it will or will not be available in the future).

**Description:**The specific quantity is not known, but is known to be non-zero and is not specified because it makes up the bulk of the material. e.g. 'Add 10mg of ingredient X, 50mg of ingredient Y, and sufficient quantity of water to 100mL.' The null flavor would be used to express the quantity of water.

The content is greater than zero, but too small to be quantified.