Is there an application that filters images by custom XMP fields?

Question

Photo

Good afternoon!
I was faced with the task of cataloging a certain number of images, mainly in JPG and PNG formats, lying in one folder. At the same time, this folder can be synchronized with other computers via Google Drive / Dropbox / another cloud, or even simply copied to media and transferred manually, after which the ability to organize and filter files should remain.
If you use just a hierarchical structure of subfolders - categories, then problems arise: it is not clear what to do if the image belongs to two or more categories at once; the subfolder structure may change or be lost altogether, leaving only the files themselves in one folder.
Another option is to use apps like Picasa or ACDSee. But they do not understand where the catalog of categories itself is stored, according to which filtering and synchronization with other devices is carried out, either absent or tied to their services.
Thus, I see the ideal solution for this task as putting XMP information inside files that would store, say, key-value pairs. It is not difficult to do this at least with the help of ExifTool, but the question arose of how to use it later?
The closest in functionality that I found is Daminion. This program seems to be able to work with user-defined tags. But in fact, the following happens: inside the program, you can create a tag (for example, Testtag), the description of which will be stored somewhere in the program files, and an XMP element will be placed inside the image, we see that the daminion namespace is created. Now, if you delete the tag description in the program itself, but do not delete the tag from the file, then even after re-importing such an image, Daminion will not see its own tags, despite the fact that there is an XMP element with the daminion namespace inside the image. This is important for several reasons: firstly, after synchronizing images to another computer, Daminion installed there will not be able to "pick up" its own tags. Second, tags
Actually the question is: is there a program that could bypass all images located in a certain folder and its subfolders, find an XMP section inside each file, find all namespaces inside it, make a list of all elements related to all namespaces and offer the user this list as a filter?
I understand that it is quite simple to create such a program algorithmically, but it became interesting, suddenly there are already similar implementations.

Answer 1

digiKam is a special tool for organizing huge "heaps" with thousands of pictures.
Able to work with EXIF/IPTC/XMP. It has its own tag system with filtering by tags, automatic initial filling of the tag database from IPTC/XMP. It has two modes: write/not_write to the images themselves changes in tags that are made in their own database.