Archiving photos: DNG, XMP and container

[Henrik Hemrin]

To save photos and related data to be accessible in long term is 
interesting. The chapter Keep Up With Technology recommends to convert 
RAW to DNG, and to place everything including XMP inside a DNG Container.

If I want to do as above, I am still uncertain of procedure in detail.

1)
Should I best convert it to DNG directly, before I do any editing, 
versions, tagging, face tagging, description etc, or when should I best 
convert it to DNG?

2)
And how do I put the XMP into a DNG Container? Is that done at writing 
meta data to file? Write to sidecar will as I understand place the XMP 
file outside the container as a separate file. The word "container" is 
for me multiple files in a container, but here I am not sure if DNG is 
the container or if it should be another DNG layer. Maybe I have missed 
something in my reading, apologize if that is the case.

Reference: 
https://docs.digikam.org/en/asset_management/data_protection.html#keep-up-with-technology

Best regards
Henrik Hemrin