During a more detail discussion about the long term maintenance, WMDA DD technique group - XSD group come up to the following update strategies from now on:

• XSD main version like 2.1 and 2.2, will be updated yearly, Q4 is preferred
  Check the XSD update timeline based on known RFCs and other request in DD member public page
  https://share.wmda.info/x/GIt0Ew
• Small changes that have no effect to the structure are possible to be arranged quarterly with version number like 2.2.1, 2.2.2
• WMDA data upload system will always support 2 XSD versions
• XSD transition period is one year for organizations