Darktable Tags (changed, applied styles and filetype) are written in the wrong section in XMP

[rekcodocker]

Describe the bug

Since version 5, DT is writing tags in these two sections:

   <dc:subject>
    <rdf:Bag>
     <rdf:li>1. Develop Filmic</rdf:li>
     <rdf:li>changed</rdf:li>
     <rdf:li>rw2</rdf:li>
    </rdf:Bag>
   </dc:subject>
   <lr:hierarchicalSubject>
    <rdf:Bag>
     <rdf:li>darktable|changed</rdf:li>
     <rdf:li>darktable|format|rw2</rdf:li>
     <rdf:li>darktable|style|1. Develop Filmic</rdf:li>
    </rdf:Bag>
   </lr:hierarchicalSubject>

(emphasis mine)

The problem is: dc:subject and lr:hierarchical subject are used for user-tagging. Tags by me.
I apply tags to photos in another program (Digikam) and this is the section where they are stored.

The edit-information from DT now:

• shows in Digikam, mixed in with the subject-tags
• when exported, shows up in viewer-software, mixed in with the subject-tags

I think these tags should not be in this section at all. They are not 'subjects'.

Steps to reproduce

Open an image file.
Make some modifications. Apply a style.
Close DT.
Open the XMP file and see that there are now tags added to the subject and LR-hierarchical subject sections.

Expected behavior

Put this editing-information in another section of the XMP file, not in subject or LR:hierarchical subject.

Logfile | Screenshot | Screencast

No response

Commit

No response

Where did you obtain darktable from?

downloaded from www.darktable.org

darktable version

5.0

What OS are you using?

Linux

What is the version of your OS?

Linux Mint

Describe your system?

Laptop Intel based

Are you using OpenCL GPU in darktable?

Yes

If yes, what is the GPU card and driver?

Intel

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

No response

[wpferguson]

The problem is: dc:subject and lr:hierarchical subject are used for user-tagging. Tags by me.

Where is this defined? Is there a reference document or specification somewhere?

Can't digikam filter tags?

See #18154.