Re: Updated group API changes draft

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On 2005.03.23 14:56 Quincey Koziol wrote:

Hi all,
    I've spent some time updating my previous draft of changes to the
group API
as a result of the changes necessary to provide "creation order"
support for
users.  I've attached the original version and the updated 2nd draft
below.
    Please send me feedback, as I'll be starting coding on this soon.

    Quincey


Thanks Quincey.  I know you have been really sweating on this one.



From talking with Quincey, I would like to point out a couple of areas
where people might want to look carefully. 1. H5Gmove, etc. 

Technically, time stamps are set when an object is inserted in a group.
And technically, H5Gmove is an atomic (delete, then insert). So it should 
set the time stamp to the time of the move.

Quincey proposes to not update the time.
There are arguments for either behavior, so it would be good for people to 
look at this carefully.


2. H5Gset_creation_time

This is a funny function that let's you manually set the timestamp on
a given link.  I'm not sure we need this at this time.

As far as I know, we don't have any use cases for this feature.
To me, it is philosophically questionable, because the timestamp isn't supposed to be "whatever I want it to be", it is supposed to be "the time I really did it". 

Also, I can think of at least 2 pernicious uses of this feature:
a) somebody my use this timestamp as a back door way to create an arbitrary 
numeric index.  E.g., compute some statistic in the dataset, and set the
timestamp to that value.  Voila! I have an index on that statistic!
b) somebody might do something horrid like store every record in a separate dataset, setting the time step from some source such as a real time clock 
or network time stamp. They are trying to get time sorted records (think
of Boeing, merging multiple real time streams.) This would kind of work, 
but I think it would be a really bad use of HDF5.

Again, others may well have different opinions, so it would be good for
people to look at this one.
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