If I interpret the ticket correctly, the problem is, that when creating a new table in the dmn demo, that I can download the table without providing the id.

It is actually not possible to remove the id once set (you can change it though), see CAM-4322

Therefore, I fixed it by setting a standard id in the empty table seed: https://github.com/dmn-io/dmn-js-examples/commit/6bdad8c65dd51f4c343dbdb4bbeb5f38a3ac8338

Yes, the problem was that an empty id="" attribute was serialized. That is not valid xml and won't parse... (AFAIK)

What should happen when I import a table without id and name? Should the dmn modeler repair the table?

Import:
If repairing is easy, then we should repair.
Alternative: reject import of the model with comprehensive error message

Export:
All models exported by the the editor should have valid ids.

Repairing should be easy, but I am not sure if we should do it.

If the user uses only our dmn modeler, his dmn files will always have an id. So if a user imports a dmn file without this id, there is most likely a reason for that. Either the dmn file comes from another modeling tool that does not support ids and will possibly break if an id is provided. Or the user deliberately deleted the id. In both cases it may not be expected by the user, that an id magically appears.

My proposal: Accept the import without an id, display the table without the id, but present a warning message to the user that this is not valid xml.

We should make sure that we only export valid xml. That means:

We import tables with the id attribute missing. If the user does not enter an id, the attribute stays missing.
We should repair tables where the id attribute is set to empty string when importing them.

commit: https://github.com/bpmn-io/dmn-js/commit/a83785e0da1fb0dfffe292622e109c5871ef55f4