> This kind of grammar theead usually ends in tears. Too right. And, no doubt, we are shortly to be thoroughly flamed for being off-topic. I think what it points out is that, those of us who do not know enough about grammar, should not presume to suggest that fixes to grammar are unimportant. Bar-room gramarians are, perhaps, as unhelpful in the IETF as bar-room lawyers, and the reason why we stoop to employ professionals is because we are not qualified to distinguish our defining elbows from our non-restrictive arses. You might go to Strunk and White for a good and clear view of the topic since this work is particular to the American usage that we are required to turn out our RFCs in. "That" is the defining, or restrictive, pronoun, "which" the nondefining, or nonrestrictive... But it would be a convenience to all if these two pronouns were used with precision. Careful writers go which-hunting, remove the defining whiches, and by so doing improve their work. If you have time, you should read Fowler's essayon the topic and extensive examples (prefering an old edition since modern editors have tended to remove his "ramblings" in later editions). He gives a simple sentence that should clearly illustrate the difference... I always buy his books that/which have influenced me greatly. Buy them all - "which" Buy a subset - "that" Better yet, let us construct an example in the context of a protocol definition... The defined protocol error conditions which/that are carried in the Notify message are for information only and MUST NOT cause any change in the processing rules. "which" - all defined protocol error conditions are for information only, they are carried in the Notify message. "that" - the protocol error conditions carried in the Notify message are for information only, but there may be other error conditions. Cheers, Adrian PS. I thought the Chicago definition clear, and the example poor. _______________________________________________ Ietf@xxxxxxxx http://www.ietf.org/mailman/listinfo/ietf