[Digikam-users] IPTC: Person Shown / PersonInImage [Take 2]

Jean-François Rabasse jean-francois.rabasse at wanadoo.fr
Tue Apr 16 13:46:19 BST 2013

On Tue, 16 Apr 2013, Jack Tummers wrote:

> This is a bit off topic, but I find this iptc/xmp very confusing
> sometimes. In Digikam they both show about the same fields
> (under 'edit all metadata'), but which one to use? Is one of
> them enough?

It's confusing for historical reasons. Standards can never be
perfect (nothing of what humans do is perfect:-) and year after
year, new things appear, new needs appear, and new standards are
created, supposed to be *better* than previous ones.

When one looks at a very old metadata action, labelling an image
(call it title, or headline, or comment, whatever), a first
proposal came with the JPEG standard, having a comment section in
files. Later came the Exif standard, rather for more technical
information but coming from Japan. And Japanese people, as all
other Asian people, are not always very happy with the
American/Ascii characters set, so the Exif User comment was
introduced with Unicode support. Later came XMP standard and the
Dublin Core schema. DC decided to feature a title in multilingual
format. This is a great enhancement to share information between
different countries but this is « Yet another title field ».
(In the meantime, between Exif comment and XMP dc:title, we also
had IPTC Headline:-)

It's impossible, when a new standard comes, to remove all previous
existing, due to the millions of existing documents and the
thousands of application software using it.
And that's why we have today many places to store things that
sounds more or less the same.

> It would be easier if everything could be done through the panel
> on the right, instead of two places.

The problem applications developers have to face is first to
select a subset of properties, that's what does the panel on the
right you mention, then to choose *where* to store that.
And there's no solution, it's too user dependent. Making decisions
about where to store such or such data means deciding that things
that looks more or less the same *are* the same. At a moment,
earlier versions of Digikam did store titles in 4 places.
(XMP dc:title, IPTC headline, Exif Usercomment, JPEG comment).

Some users may agree with that, and some other may disagree.
(I personally disagree because I don't consider dc:title,
exif:comment, jpeg:comment, to be the same and I already had data
destroyed in images having different values in these fields.
But it's my problem, not DK problem.)

I still believe the ideal solution is to let management software
choose their editable data subset, choose one and only one place
to save, and let the user manage metadata from outside,
with reorganisation tools (e.g. replicate the dc:title value to
exif:comment, or get my persons tags and (re)build IPTC Person in

And this is out of images collections management programs, because
it relies also on programs that will use that metadata. Metadata
storage are to be used and are expected to support interoperability.

E.g. a program that build web pages with images may use image
title to set a page title (the HTML <title>....</title> markup).
But where to find the image title ? In dc:title,
in iptc:headline ? And if both fields exist, with different values ?

No ideal solution is to be expected, sad but true:-)


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