In X12.3 Implementation guide, section B.1.1.3.4 String says, "The string data element must contain at least one non-space character.... The representation of this element is AN".
Required Clarification:
1- Must ISA02 or ISA04 contain a non-space character when ISA01 and ISA03, respectively, contains code 00?
2- This clarification request was raised in 2001 but still all the IG have same information, is there any update done on this or will be done in future.?
http://www.x12.org/rfis/ISA02%20and%20ISA04%20Content.pdf
3 - Is there any official/public update on this exception, clarifying usages which can be considered as standard for implementation?
All-space values in ISA02 or ISA04 are valid in an ISA segment.
X12C recognizes a minor apparent conflict about this validity in our reference documents. X12C will undertake data maintenance to address this issue.
Additional Information:
ISA elements 02 and 04 are fixed in length with identical minimum and maximum lengths. Spaces are inserted to meet the minimum length in an AN data element. With the associated code 00 in ISA01 or ISA03, an all space value in ISA02 or ISA04 indicates no information.
X12.5, Section 4.4.1, makes explicit mention of the combination of a code 00 being paired with "no_information" which is defined ten spaces for ISA02 and ISA04.