Hi all,
I am new to DigiKam, but somehow I think the following is possible. I hope so, I really like DigiKam. Working on Windows 10 at moment. I am a family image archivist, not a professional photographer. So much EXIF info is unimportant to me. But the family-oriented information is priceless .

I have an unusual approach to sidecar files, I presume xmp sidecar files. I want the key data to be written to sidecar files 100% of the time. My key data is:
* Title
* Description
* Keytags
* Date Created
* GeoLocation

My goal is to have my photos be readable 50-100 years from now. I do not trust embedded information at all. I want it all in XML based sidecar files.
I also want to be able to rebuild my database from the photos plus sidecar files, to repopulate the database with the above information.
In other words, I like the speed of a database, but want total assurance the data is in readable sidecar files also.

My main filetypes are TIF, JPG, PNG, PDF, MP3, MP4 and AVI.

I sort of think I will need to change switches in DigiKam to a) write this data out to Sidecar files every day, and b) on rare occasion, READ into a new database all the Sidecar information, so the above fields repopulate.

1. "Creation Mode" - Can someone help me know how to set up to write 100% of the time to sidecars, so sidecars are always created and populated with the above information. Call this "creation mode" for creating and populating sidecars.
2. "Rebuild Mode" - And then how to change DigiKam so a new database will read all the sidecar files and rebuild the database? Call this "rebuild mode". I realize after rebuilding, I would need to set DigiKam back to "creation mode" after the rebuild. This is rebuilding the database from the sidecar files.

Part of my motivation is to be able to give someone a set of folders with images and sidecar files, and tell them to install DigiKam, and import the pictures, and have all the sidecar information end up in their database. I don't mind telling them what settings in DigiKam to use, that would be part of the instructions. A great way to share family archives.
Thank you.

I have answered my own questions. I spent some time testing digikam with various files and folders, and basically, out of the box it does what I want splendidly. If I transfer a folder with images and sidecar files to a new Windows 10 PC and install digikam and open the folder, all the tags and information is read correctly from the sidecar files.
In order to get digikam to WRITE out to sidecar files every time, I did go to SETTINGS/CONFIGURE DIGIKAM/SIDECARS and changed to defaults to the following:
* Read from sidecar files - CHECK
* Write to sidecar files - CHECK
* Write to item and XMP sidecar - SELECTED

That was all that was necessary for digikam to write 100% of the time to sidecar files.
Then when entering Metadata, I open the Tag Manager, and use the Information and Description tabs. The information there gets written to the sidecar file as well.

A beautiful slightly unexpected feature is that opening a file with images and sidecar files in several other programs brings the data in perfectly:
* Lightroom
* Darktable
* Photools Imatch

So, digicam is powerful and easy to use, and exactly what I want as a beginner family archivist trying to preserve tags and metadata for 100 years in ASCII text files, XML format .

The original posting, questions and statements are old, but good and still valid!

I can confirm, that Digikam is one of the few tools, which does work perfectly together
with other sidecar (XMP file) based tools.

I have deep and troublesome experience with Idimager, Photosupreme, Mediapro, Lightroom, Xnview, Imatch and other DAM tools.
My main problem was the handling of read-only image files (JPG, RAW, DNG and all others!).
A lot of DAM tools are unflexible with this! And a couple of tools even do not respect read-only image files.

Meanwhile I am using Digikam for tag management with write-only <name>.XMP sidecars.
Only during the first import of images, the metadata files are imported to Digikam and saved after the first edit to XMP.

In parallel I am using Darktable for RAW/DNG and JPG editing with separate read-write <name>.<ext>.XMP sidecars.
I do not need the tags from Digikam in Darktable and I do not want the raw edits of Darktable in the XMPs of Digikam.
With this Digikam is used only as a DAM tool and Darktable is only used for nondestructive editing.
There is no need for (and no risk with) metadata sync between both sidecar based tools.
An both the tags, colors, ratings, groups of Digikam and the edits of Darktable are saved in XMP sidecars.
A file backup or versioning is much faster and secure, when the original images are kept untouched.