3. Terminology

This memo does not use the oft used expressions MUST, SHOULD, MAY, or their negative forms. In some sections it may seem that a specification is worded mildly, and hence some may infer that the specification is optional. That is not correct. Anywhere that this memo suggests that some action should be carried out, or must be carried out, or that some behaviour is acceptable, or not, that is to be considered as a fundamental aspect of this specification, regardless of the specific words used. If some behaviour or action is truly optional, that will be clearly specified by the text.