Hologlyph

A hologlyph was a holographic representation of a person. They were able to think by themselves, and could be created even after the person they were based on was deceased. Book was a hologlyph who assisted Osefa de Palabra Hftzbrn in her work on The Lexicon. Shortly after Osefa's death, the Sixth Doctor created a Hologlyph of her, hoping to find out about how she had died. However, the hologlyph was convinced that it was the real Osefa, and thus did not prove to be helpful.