Former wife of Dr. Noonien Soong. Juliana was killed during an attack by the Crystalline Entity at Omicron Theta.
Dr. Tainer could be considered the "mother" of the androids Data and Lore, as she helped to raise them from the android equivalent of infancy.
Although Dr. Soong's wife is deceased, he created an android replica which, in the Star Trek universe, is still alive and functioning, and married to a Mr. Tainer. Although Data discovered that she was an android (mainly by detecting a pattern in her blinking), he decided it would be best not to tell her.
The Star Trek Project