All business projects using the Kmehr standard need to comply to this Kmehr standard.
The XML scheme definition of the kmehr-standard (.XSD file) can be found at External Links#kmehr_message-overview.
The definition has evolved over the years, and is still in evolution.
All versions of the XSchema can be found at External Links#kmehr_message-xschema.
For Vitalink, it depends on the business project to know which XSchema was used as reference. For each business project, this will be defined in the corresponding documentation.