How to delete things from write protected dvd

Is the disk a DVD-R or +R or is it a Re-writable disk (-RW or +RW).
If the DVD is just a -R or +R and has files written to it and the disk closed for writing I think the only way to delete a file is "Cut it up in pieces" They are wtite ONCE, Read many times. IR it is a RW (rewritable) disk, then probably you could change the Attribute.