Message Containers and Versioning
Our mission is to create an interface which is backwards compatible within a major version. Backwards compatible we define as never changing existing elements and types but only adding new ones, making them optional. Thus a message of version x.y will be completely valid in x.y+1 while x.y+1 messages will not necessarily validate in x.y but may be used when not validated against the schema.
We encourage using several versions at the same time to ease transitions and migrating to new (minor or major) versions. A version is defined as the set of schemas excluding the container StringMessage (and the DrvGlobalTypes which are not part of the STRING project).
A StringMessage is a generic request/response pair containing versioning information and a <Content> element defined as xs:anyType which will contain the payload valid for the given version. An empty StringMessage should be replied to with the list of valid versions for the operator system.