The value of this attribute should represent a date (in standard yyyy-mm-dd format) which is later than the date on which the attribute is added to an ODD. Technically, this attribute asserts only the intent to leave a construct in future releases of the markup language being defined up to at least the specified date, and makes no assertion about what happens past that date. In practice, the expectation is that the construct will be removed from future releases of the markup language being defined sometime shortly after the validUntil date.

An ODD processor will typically not process a specification element which has a validUntil date that is in the past. An ODD processor will typically warn users about constructs which have a validUntil date that is in the future. E.g., the documentation for such a construct might include the phrase warning: deprecated in red.