Help - "full Ball Attire" Required

Question : what attire may i wear for attending a formal Ball ???
For my job, I am invited to the First release of a New Great `Viennese` Ball in a country of Central Europa (new ECC), next spring.It will take place in an old palace.I am aware that I must indeed wear some evening dress, but what exactly is the recommanded attire to be "in" as a guest of honour to this affair? The english (and german and local language written) program tells : « The 1st xxx Ball is a very formal affair, white tie … Ladies may wear a full ball attire. » What is this "FULL ball attire" required ??? thanks to everyone ! Lauriane 29y old French woman.