I have made a different experience:
write = update,edit,delete
delete = nothing in the context of file storage
create = nothing in the context of file storage
Also scenarios as described are not definable.
Also webdav doesn't work very well with microsoft. it sure is a microsoft issue but that I cannot tell the users. they want it to work properly. thus the question is: has anyone take a deeper look into what is required to be done to get it work smoothly?