This question came up today at the NASA briefing, when we were talking
about the netCDF 4 project. There was a weak but immediate and negative
reaction to using time as a proxy for creation order. The reason given was
that many applications would want to use the creation time as an attribute,
but that the times used would not necessarily give the same ordering as
creation time because different times might be relative to different time
zones. I have a feeling there were other cases, given the reaction people had.
Of course this could only happen if people were allowed to change the
"creation time." And one could also argue that creation time is a
different attribute -- it's the time the link was created, not the time the
data was collected. But I have a feeling this would just lead to confusion.
So at best, I think there is concern that this could led to confusion. I
tend to agree.
At 10:16 AM 4/19/2005, Quincey Koziol wrote:
> Quincey Koziol <koziol@xxxxxxxxxxxxx> writes:
> > I was planning on including a hidden field to disambiguate
> > were created at the same time, so this wouldn't happen. Since there's no
> > advantage to using a creation order field instead of using the
> > when determining the n'th object inserted into a group (when
> > objects into the equation), I'm still leaning toward using a time
instead of an
> > index for this purpose. Using the time provides the same
> > adds information as well.
> > I'm still somewhat split on the issue however and would welcome
> > arguments in favor of one mechanism or the other. :-) I'm also
> > including both fields (creation order and creation time) and allowing
> > create an index on either, to suit their particular needs...
> What happens is a machine with an inaccurate time adds a variable to a
It'll get the "wrong" creation time and inserted in the index
appropriately, as you'd expect. I don't think this is a major problem though,
because I don't think that most files will get edited on multiple machines in
a very short timeframe.
Mike Folk, Scientific Data Tech (HDF) http://hdf.ncsa.uiuc.edu
NCSA/U of Illinois at Urbana-Champaign 217-244-0647 voice
605 E. Springfield Ave., Champaign IL 61820 217-244-1987 fax