QFTP — include the rationale for not declaring QoSDimension as tagged values

The profile requires two stereotypes to be applied simultaneously (QoSDimension and QoSCharacteristic). This is untidy, although I can see from the examples later in the document that QoSDimension is applied to attributes when QoSCharacteristic is applied to a class. The document, at least, should include the rationale for not declaring QoSDimension as tagged values (fig 8-3 on page 11).