Memories are encoded within the physical structure of the brain on the molecular level. Uploading is the process of copying all this information into a digital form. These upload recordings can be used to create a mind emulation, a computer program that, when run on a sufficiently potent computer, emulates the workings of the original person's mind.
A mind emulation is not merely a recording, but a conscious, self-aware, working digital model of the way a particular living being's brain functions. This requires simulating much of the rest of the body and its environment as well: 'naked consciousness' bereft of context rapidly becomes insane.
Mind emulations can be housed in computers contained within bioshells or cybershells. Those without mobile bodies inhabit virtual reality simulations of, at minimum, a room. They are often permitted to access the wider Web itself, allowing them to partake of online virtual realities.
Emulations are usually made of human minds, but animals can be emulated. The legal status of human mind emulations varies between nations: some treat them as artificial intelligence, others as people. There are three types of mind emulation:
A 'ghost' is created via destructive uploading (or 'brainpeeling') process. A living or newly dead patient (or his severed head) is placed into nanostasis. The brain is removed and carefully sliced by robotic surgeons into multiple tiny segments. Each segment is then scanned by a hypersensitive magnetic resonance imager (HyMRI) or other instrument. The data is used to create a digital reconstruction of the patient's brain configuration, called a ghost.
Brainpeeling is fatal to the original person, so ghosts are controversial. Is it suicide or transcendence? A ghost is a perfect mind emulation, mentally indistinguishable from the original person. People and religions that believe in souls differ on whether ghosts have them. Ghosts require a great deal of computer power to run, equivalent to a sapient AI, but current computers are sophisticated enough that a ghost can be built into a computer small enough to be implanted in a brain.
Most ghosts are the product of individuals who deliberately underwent destructive uploading in order to obtain a form of immortality, often out of a desire to live as a posthuman entity in a superhuman cybershell body or series of bodies. Ghosts have certain advantages: for example, they allow rapid travel across the solar system and beyond, if a receiving station has been set up. Ghosts are also cheaper than full-scale cellular rejuvenation technology. Perhaps most significantly, a ghost can be copied indefinitely. It is against the law in nearly all nations for a person to exist as more than one conscious ghost, but it is legal to create backups of the original or the ghost's current state. Copying either is as simple as copying any other computer program: each backup requires hundreds of terabytes of storage, but that is easy to come by.
The big drawback of ghosts is the question of whether it's really you or just something that thinks it is. The other drawback is that uploading is a complex medical procedure, and once in a while, the operation fails. This usually results in a badly flawed copy or no copy at all.
A 'fragment' results from a failed attempt to create a ghost. It has little or no memory of its past existence, but may retain vestiges of its original personality and skills. Fragments are often produced when attempting to destructively upload a person who, after dying, was not immediately placed in nanostasis. If he was frozen using older cryonics techniques, or there was a delay of several minutes or more, then there is a high likelihood of retrieving only a fragment rather than a ghost. In areas where ghosts are treated like people, fragments are treated like people with mental illness or amnesia.
Shadows have all the advantages of ghosts, can be run on less powerful computers, and take up less data storage space. They have one big disadvantage: it is clear they aren't quite identical to the original.
Shadows are generally created through a nondestructive mind emulation process ('brainscanning'). This process uses nanoprobe monitoring to provide data for a computer model. A shadow is basically a low-sapient aI that has been taught to behave like a person. (A sapient AI has already become a person.) Editing a ghost or fragment can also produce a shadow. This is as much an art as a science, but it will generally produce a more compressed copy suitable for running on a less powerful system.
Shadows are legal in most blocs except the Islamic Caliphate, but are generally treated as property rather than actual people. Multiple copying of shadows is legal in some areas, strongly regulated in others.