[Digikam-users] digikam not showing Darwin Core metadata

[Jean-François Rabasse]

On Tue, 26 Nov 2013, Alan Pater wrote:

> Darwin Core is a set of XMP metadata for use by biologists working in the
> field. It allows them to add metadata for things like the species name,
> age, sex, etc.
>
> That data does not show up in digikam. Is there something I have to toggle
> to get it to show?
>
> Exiv2 can show the data:

Hello Alan,

My comments, as I have similar issues when using non standard XMP 
professional schemas or private schemas.
(When I say « non standard », I mean valid schemas used by such or such 
community to handle data not provided by the basic XMP schemas, as
XMP Basic, Dublin Core, Exif, Media Management, et al.)

The XMP format (RDF/XML based) allows any metadata reading application
to read/display any property, even from unknown schemas.
And that's why exiv2 shows up all your dwc data.

But, to edit/rewrite XMP properties an application must know the schema
and properties types.

And Digikam has metadata edition features, so it can be seen as a XMP
read/write application. And that's why, if you look into the XMP 
properties list (Settings > Metadata > Display > XMP viewer) you'll
find only « known » properties, i.e. the basic XMP schemas, and none
of the dozen of professional or private extensions.

If you just wish to view your data, a metadata reader could do because,
cf. supra, even unknown properties can be displayed.
You can use command line tools, as you did with exiv2, or some images
browers/viewers. As for me I use the tandem Dolphin+Gwenview and 
Gwenview shows all existing XMP data, known or unknown.

If you wish to edit your data too, you'll have to use a specific 
application aware of the dwc schema (I'm not a biologist and I don't 
know what software exist), or to use a configurable metadata editor.
I am a exiftool user, and with exiftool it's possible to declare any
XMP schema your need, a known schema as dwc or private schemas, in the
~/.ExifTool_config file. This will make exiftool aware of your data and
you will be able to edit, modify, remove, not just read.

(Perhaps the same thing, extended schemas configuration, is possible 
with exiv2 but I don't known the syntax.)

Regards,
Jean-François