Ed, You raise two issues: (1) The default should be "unstated reliability" rather than "certainly unknown" as I had suggested. That's fine with me. So '1984?' would carry the implicit semantics "uncertain, but level of uncertainly unstated". (2) Extensibility or not. There are two ways to do this, I think. One is to declare this model to be explicitly non-extensible and define a closed controlled vocabulary. The other would be a model based on assigning URIs for the levels. The first is what I thought you wanted, and since you are perhaps the only member of this forum interested in uncertainly - that is, going beyond simply asserting that a value is uncertain, and actually assigning an uncertainly level - then my only interest is in ensuring that whatever model we adopt, it does not affect those who simply want unqualified uncertainly. And if a closed, controlled vocabulary meets your needs - and it certainly does seem to be the least complex approach - then I think it's fine. However, if you want the model to be extensible (and presumably we would want decentralized extensibility) then I think we need to allow a URI within the string where the URI identifies a level of uncertainty. Do you want to pursue this approach? --Ray From: Discussion of the Developing Date/Time Standards [mailto:[log in to unmask]] On Behalf Of Edward C. Zimmermann Sent: Friday, February 04, 2011 2:27 AM To: [log in to unmask] Subject: Re: [DATETIME] uncertainty and precision On Thu, 3 Feb 2011 11:24:30 -0500, Ray Denenberg, Library of Congress wrote > (I changed subject of this thread, it was "uncertainty".) I would change the topic to "data reliability". Uncertainty is an attribute. Precision is also something else.. > Take "uncertainty" first. If we say that ? may be followed by a measure of uncertainty we have to be careful because ? does not always end the entire string. For example: (2004)?06-1. However if we say that uncertainty is indicated by one of the letters a, b, c, d, e, then we don't introduce ambiguity because in the current draft there isn't any case where ? would be followed by one of these letters. > > So the question is: Are Ed's suggested set of values acceptable to indicate uncertainty: > - a) Known to be correct (observed, documented etc.) > - b) Likely correct ( p> 50%) > - c) Possibly correct (Might be but not likely) > - d) Likely incorrect (The date is expected to be wrong p ~ 0) > - e) Unknown (certainty unknown). > Actually I would eliminate (e); "certainty unknown" should be the default - it should not be mandatory for the ? to be followed by an uncertainly level. > 1) I think the default is "unstated reliability". For the reciever there is perhaps little difference but they are not the same just as the (a) case is equivalent to the reciever but not the "same" as the non-specified case, e.g. (X)?a versus (X) 2) I am not quite sure that using letters is the best approach since it locks things too much down and prevents extension... I can well envision profiles where people have finer semantics such as "most certainty correct (but possibly wrong)". Recall these are also dependent upon states of knowledge. The assertion, for example, that that the Earth was the center of celestial spheres was "known" to be correct and confirmed by observation (including those of Ptolemy and Copernicus). Tycho Brahe established a new standard of observations and that formed the basis for Keppler's work (and a paradigm change).... > Next, precision. Similarly, ~ could be followed by a level of precision. Simon, would you like to propose a scheme? Here we should to talk instead about "readability". > > --Ray