Ira Graves, PhD, was a male Human who was an expert in the field of cybernetics, specifically molecular cybernetics, who lived during in the mid-24th century. Doctor Graves was believed to be one of the finest scientific minds of his time.
During his career, Graves had a lot of contact with Dr. Noonian Soong and claimed to have taught him everything he knew. When Graves met Soong's creation, Data, he suggested the fact that he educated Data's creator made him his "grandfather".
Late in his life, Graves retired to Gravesworld, where he lived in virtual solitude, save for his assistant Kareen Brianon. His work continued there, and, by 2365, it had reached a critical stage. He had planned to transfer his wealth of knowledge, his great intelligence into a computer.
Graves had also secretly fallen in love with Kareen, regretting the difference in their respective ages and finding himself too old for her.
Graves had begun to suffer from Darnay's disease. He suspected an illness, but did not seek a doctor's help since he planned to survive through a computer. However, Kareen secretly signaled for help and Starfleet sent the USS Enterprise-D. He then met Data for the first time, and saw an unexpected opportunity to usurp control of Data's body, after which his original body died. He located Data deactivation switch, and transferred his mind into data's frame, only to find that more of his "self" than he imagined, including his feelings and dreams, would be retained. His body was eventually beamed from the Enterprise into space aboard a torpedo casing.
Graves' essence existed in Data like a split personality exhibiting dominance over Data's. Although Graves initially tried to hide this fact, it quickly became apparent as his personality became unstable. After realizing that he had become a danger to others, Graves chose to leave Data's body and transfer himself to the Enterprise main computer. This allowed his vast knowledge to be stored permanently, although the Human element could not be salvaged. (TNG: "The Schizoid Man")
Doctor Graves was played by W. Morgan Sheppard in his Human form and by Brent Spiner when Graves was in control of Data's body. In the episode's script, he was described as a quantum physicist and was in his late seventies, which suggests he was born between the mid-2280s and mid-2290s.  StarTrek.com described him as a molecular cyberneticist. 
Two certificates naming Graves as the Sirius Cybernetics Corporation "Humanoid of the Year" and referencing the Zee-Magnees Prize from the Zee Magnees Institute for Theoretical Research were created as set dressing, though did not appear on screen. The artwork was depicted in Star Trek: The Next Generation - The Continuing Mission (p. 76)
The episode and the title were intended by the episode's writer Tracy Tormé as an homage to the British television series The Prisoner. One of the episodes in that series was titled "The Schizoid Man". During casting for the episode, the star of this series, Patrick McGoohan, was considered for the role of Dr. Ira Graves. (Star Trek Encyclopedia (4th ed., vol. 2, p. 256))
The computerized Ira Graves featured several in-jokes, including another reference to the Japanese series Dirty Pair in the form of "Kal(Yu/RJ) = DP (Angle)". (See 'Kei', 'Yuri', 'Dirty Pair', and 'Lovely Angels')