Validation Rules represent validation that is performed on a message on the segment level. What distinguishes validation rules from strict grammar checking for segment grammars is that validation rules can take multiple forms, and can use multiple fields of a segment to determine its validity.

For example, if some field matches a certain value, then the current field must match a different value. This is useful for checking field validity based on a code value. For instance, checking that a field matches a particular phone number format if the qualifier field is "PH".

All Validation Rules use the Error Code 0x80002006. Additional information about the error is contained within the key-value pairs of the thrown exception.

The Message Parsing Errors parameters are also included in the exception.