[Digikam-users] digikam not showing Darwin Core metadata

Remco Viëtor remco.vietor at wanadoo.fr
Tue Nov 26 12:30:19 GMT 2013

On Tuesday 26 November 2013 10:34:55 Jean-François Rabasse wrote:
> (...)
> PS: my personal opinion is that non standard (or as Gilles said, non 
> strictly photographic data) support is a complicated problem.
> XMP has been thought to be extensible, the X stands for that, and many
> schemas exist in different communities.
> Should an application software as Digikam implement (hard coded) all
> existing schema and ingest all new schemas as they are created ?
> Sounds like an endless task.
> Perhaps a good direction could be to use specific configuration files
> a user could setup to describe relevant data ?
> (In my previous message I mentionned exiftool because Phil Harvey 
> decided not to implement all possible schemas, but to feature a syntax
> and configuration file .ExifTool_config to let the user declare
> anything. Looks probably the only solution to support extensibility.)

The nice thing about XMP: it's is a variant on XML, so there is no need to 
configure which schemas to accept, as each piece of information has its 
name available as well. You'd only need configuration options if you want 
to show only /some/ of the fields.

That's also why Exiv2 can easily display all XMP metadata, with no need for
guessing at tags or values: they are all in the metadata)

Note that all this concerns *XMP* metadata only, EXIF and IPTC data are 
different (for starters, the EXIF data has binary and fixed size fields,  
no tag names included in the image file, and even a field with undefined 
structure: the makernote area). Then again, OP's question was about XMP 
data only.


=== "technical" exemple following, can be ignored ;) ===

This is what I found in one of my images:
<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP Core 4.4.0-Exiv2"> 
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> 
<rdf:Description rdf:about="" 

Note all the "xmlns:..." lines. Those lines indicate what 
schemas/namespaces are used, but they do *not* indicate where to find the 
definitions (DTD), their only function is to generate a unique name for the 
namespace (unfortunately for us...).

If the DTD for a given schema is available, it should be possible to 
generate a settings dialog to define what information to show 'on the fly'.
Without it, we would be limited to show all or nothing per namespace, as we 
cannot be sure to cover all possible tags within th namespace.

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