This URL, https://nws.weather.gov/schemas/iwxxm-us, shall be the canonical location for the IWXXM-US schemas. These schemas are to support supplemental information and the Federal Aviation Administration's filed differences with the ICAO regarding Annex 3 products. The IWXXM-US schemas do not replace IWXXM. Their purpose is to allow non-Annex 3 content to appear in IWXXM form via the elements. To date the versioning history of IWXXM-US has followed in lockstep with IWXXM. While the actual differences between IWXXM-US 2.0 and 3.0 would normally designate a minor update, i.e. IWXXM-US 2.1., it was decided that with the operational and mandated practice of issuing IWXXM products beginning in 2020, less confusion would result with the stakeholders and external partners if the major numbers of IWXXM and IWXXM-US were identical at the outset. In the future, it is not required nor should there be any expectation that IWXXM-US schema versioning remain in lockstep with IWXXM's. For more details and background information on IWXXM-US schema, please visit the NWS Meteorological Development Laboratory's web page: https://vlab.noaa.gov/web/mdl/data-modeling This website is not supported 24/7 thus availablity of the schemas at all times is not guaranteed nor should this site be used to validate real-time operational data streams. Validation of XML documents should be made with local copies of the schemas. Read the 'Latest-News-and-Updates.txt' file for recent news and developments related to IWXXM-US namespace. Version 2.0 (Folder 2.0) ------------------------ Initial version. IWXXM elements first appeared with IWXXM 2.0 release. IWXXM-US UML data models were developed to take advantage of this new feature in IWXXM. This version is no longer in use by the NWS. Version 3.0 (Folder 3.0) ------------------------ Revised and updated for IWXXM 3.0 release. This version incorporates changes to the IWXXM-US UML data models to streamline and reduce the overall size (content) of the blocks within the IWXXM messages. (12 Apr 2019)