This is an answer to a comment from Bruce on my previous post, and the reason why I favor more XMP than RDF; at least at the moment. I will start by saying no decision have been taken on whether Krita should be "limited" to XMP (or RDF), or whether OpenRaster will be using XMP instead of RDF.

XMP is subset of RDF

So XMP is a subset of RDF and doesn't support all the features of RDF, and it's using an older version of RDF. I can understand that it makes it harder to use a RDF parser to manipulates XMP data, but from my point of view it's hardly a problem, as long as XMP allows to do everything I want to do in metadata in Krita. Then, I would add that supporting XMP is important because it's quiet well established in the graphic world.

XMP is not fully opened

That said I shared the same wish as Bruce that Adobe would open up more the XMP specification. But the real reason behind the current "embrace" of the Open Source world for XMP is that Adobe made the first step. While until very recently the XMP Spec was only available with a package that only Adobe could distribute, meaning they could shut down the access to XMP at any moment. But with their recent change of licensing policy, it makes XMP attractive to open source application. While adding support to XMP is unlikely to change their mind on opening more the specification, not supporting it is clearly showing Adobe that we don't care, and then why should they care ?

I also have serious doubts that if I found something lacking in a W3C specification which is as likely to happen than in XMP, they would even bother to listen to me :) So for a miserable ant like me it doesn't make a real difference.

So why, even with that bad point, I still prefer XMP over RDF ?

The first reason is that I still don't understand the full extend of RDF (after having spending quiet some times digging on the w3c or in the web), which either mean I am completely stupid or that it covers too much. While XMP is designed specifically for multimedia documents, and it has everything needed for handling the associated metadata. And I much more favor simplicity, and having more specifications instead of one that suppose to rules all the other.

I am also missing something from the Exif and IPTC schemas I found for RDF (unless I didn't see something), they don't defines the types of each fields.

XMP is vastly used in the graphics world
To finish, the main reason why I consider it is important to support XMP is that there is an increasing number of files which includes XMP metadata.