Note: We recommend to use the ECRM with the versioned namespace. Using a unversioned namespace means that a specific class or property would always be the same (in the sense of owl:sameas) no matter which version is used. However, this assumption is not valid if something changes in the definition of a class or property (new restriction, different range etc.) from one version to another. Nevertheless, if you are not interested in automated reasoning or unambiguous identifiers you can use this unversioned namespace to always refer to the most recent version of the ECRM.
Previous versions can be found here.