On Apr 19, 2012, at 5:00 AM, James Cheney wrote: > > On Apr 19, 2012, at 5:35 AM, Luc Moreau wrote: > >> Hi James, >> > ... > >> I think the confusion may have come from the description of the grammar but Paolo has reworked it. >> >> As far as the reading of - is concerned, I would even say that we have the following cases: >> - value exists and is known but not expressed (say, because not deemed important) >> - value existence is known but actual value is unknown >> - value does not exist >> - value existence is not known >> So, your suggested split absent/unknown may not be the clearest. >> >> I believe your Proposal 0 is implemented in the grammar. >> >> I considered variants of Proposal 1 but ruled them out because the grammar was not ambiguous. >> > > I would argue that the proliferation of different cases above is a strong motivation for cutting down on the number of cases. Even if the grammar happens to be unambiguous (though I can't see how it can be), we are currently asking a lot of readers especially since the grammar is the last of the three documents they'll see. > > In an open world setting (I think!) we shouldn't distinguish between "value does not exist" and "value existence is not known". +1 > Combining provenance records could fill in unknown vlaues. In any case, we currently have no way to express this distinction - and we don't say anywhere what should happen if we somehow learn the value of a "value that does not exist". > > I also see no reason to distinguish between "value exists and is known but not expressed" and "value existence is known but actual value is unknown" - from the point of view of a consumer of provenance, what would I do differently? +1 -Tim
Received on Thursday, 19 April 2012 12:26:03 UTC