[Digikam-users] What is being/will be done about the tags management problem?

[Jean-François Rabasse]

On Tue, 19 Feb 2013, jdd wrote:

> anyway, there are two ways of solving this issue, one easy, the other 
> difficult :-)
>
> * easy mode: when allowing write metadata to images, ask for an option: image 
> metadata replace database metadata ("priority to the image metadata") or 
> database metadata replace image metadata ("priority to the database 
> metadata"). The rationale is that an image can be changed from the operating 
> system (think at the reloading of backup).
>
> * difficult mode: merge the metadata in the two ways, but then I not even 
> imagine how one can sort the thing

No way !
Because of lack of information. Synchronization issues require that a
« reference » could be set, and a « outdated » be set too.
And a synchronization software needs an information to decide. In most
case a timestamp is used, as do files synchronization tools such as
rsync. The oldest stuff is considered as the outdated wrt. the newest
and will be replace by the newest.

But with XMP metadata, there's no such information. The XMP schema has
a dedicated field, xmp:MetadataDate, that should be the last time
metadata has been updated. Ideally, this field should be set 
automaticaly when writing metadata, but very few software do that.
At least, the libexiv2 doesn't, too bad :-(

So, only the user can decide which is the reference and which is the
outdated, and in which way to do the sync copy.

Anyway, with Digikam there's the « heavy » solution, when one wants the
database to be in sync with images : just delete all tags, in DK, all
tags trees, then reload metadata from images. Tags are rebuilt on
the fly and reflect exactly the images data.
That's my paleolithic technique, rought but efficient. :-)

Jean-François

NB: this is not just a tags issue, same problems occurs with other
metadata, e.g. title and caption. If you remove a title from an image,
outside Digikam, then re-read metadata, the DK database still contains
the old title, that must be removed by hand.