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Dear Jeff,Milan has covered this topic in detail, so I can hardly add anything useful to it. I can only confirm that our current practice of deprecating
descriptors leads to carelessness in specification of the table versions. Using only one set of tables may lead to producing a BUFR message containing descriptors that were introduced with higher version than it is indicated in the message. Or to processing of the data without taking into account the version number in the message.The current practice is not based on BUFR regulations, as Milan indicated. I think that it would have to be changed sooner or later, so better sooner
than later. With best regards,Eva
On 13 Aug 2008 at 12:08, Jeff.Ator@xxxxxxxx wrote:
Dear Eva and Milan, I must admit I'm confused now. While I certainly agree that it's possible, and perhaps even preferable, to be able to change the characteristics of an existing descriptor when a table version number is incremented, I don't recall that we ever formally agreed to adopt this as the new practice. Eva, I have read your 3.1.1(1) document, and I do recall when we previously discussed the problems of these particular radiation descriptors; however, I don't recall (nor do I see any mention in the final reports from any of our previous meetings?) where we agreed to this change in practice. As you mentioned, in the past we've always kept existing descriptors frozen and just deprecated and replaced them with new descriptors whenever subsequent problems were discovered. And while I certainly remember past instances where we've discussed the shortcomings (e.g. Table B classes rapidly filling up) of this type of approach, I just don't remember where we ever formally agreed to change it. I apologize if my memory on this point is faulty, and if that is the case could you please point me (and the rest of this mailing list as well!) to any relevant documentation? Personally, I have no problem with allowing descriptor characteristics to change between table versions. I do think it is workable and has several benefits, which is probably why I didn't object if/when we did previously agree to this as a group. In my below email I was only trying to describe the current policy (at least as I understood it) to my colleagues on the mailing list. As you mentioned, the big issue involved with changing this would be that the Secretariat would now have to maintain all of the old versions of the tables (and in a machine-readable format! :-) somewhere on the WMO web server. Assuming Joel is agreeable to that, then I believe the majority of my colleagues here in the U.S. would agree to it as well. Thanks and best regards, -Jeff