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Datastream is a component of computer technology dating back to Caprica before the Fall. It is later utilized by the Cylons as the primary computer network of their installations and baseships. It is usually represented by pixelated icons flowing on computer readouts or projected onto walls or bulkheads.
In the years leading up to the Cylon War, the datastream is common in computers and technology created, utilized, marked and sold by Graystone Industries. The datastream appears to make up the structure of the virtual world and is experienced as a tunnel or gateway by holoband users when transitioning into the digital realm. The datastream also appears in the holoband welcome screen, flowing below images of virtual destinations (CAP: Pilot, "Rebirth", "Know Thy Enemy").
Following the death of his daughter and the discovery of her living avatar in the virtual world, Daniel Graystone attempts to resurrect Zoe Graystone in the body of one of his company's U-87 Cyber Combat Units. The datastream facilitates the integration of the meta-cognitive processor with the U-87 chassis. During the transfer, however, the datastream is lost, corrupting the chip and seemingly deleting Zoe's virtual consciousness (CAP: Pilot").
Zoe Graystone's avatar is in fact not deleted and continues within the prototypical Cylon, experiencing the world through the eyes of her father's robotic creation. This includes datastream symbols and information entering her vision, dreams and memories (CAP: "Rebirth").
Following the first Cylon War, the Cylons utilize datastream technology, removing it from just the digital world to be accessed as a physical medium.
A datastream is first seen in a Cylon facility on occupied New Caprica, where the Colonial launch keys are held. Sharon Agathon uses her Cylon abilities to access the datastream to grant her access to the key's storage area (TRS: Exodus, Part I). On a basestar, the datastream is literally composed of a stream of water, which is used in whole or in part as a transmission medium, a storage medium, or both (TRS: "A Measure of Salvation", "Guess What's Coming To Dinner?").
Several humanoid Cylons are seen using interfaces in a basestar's command and control center that consist of a illuminated panel covered by a thin layer of water, suggesting that the liquid may serve as both display and input device as a Cylon interfaces the datastream. This behavior is reinforced by the comparative lack of visual displays throughout the command and control center. All information appears to come from these liquid data interfaces.
The interfaces are normally used by the Cylons by placing their hand on the interface, making contact with the illuminated base and the thin liquid layer, which activates the data ports within their arm. The interfaces can also be configured to show visual information such as still photography, such as the photos taken by Gaius Baltar during his exploration of a dying basestar that makes a reconnaissance mission to the Lion's Head Nebula (Torn). Sections of these pictures can be enlarged and sharpened.
The basestar's central computer, the Hybrid, rests within a pool of liquid, connected to many conduits below the surface. Clear liquid drips on the Hybrid from above the pool, suggesting that data might be relayed to and from the Hybrid through the liquid surrounding and falling upon her in some fashion.
Athena accompanies fellow members of a Colonial boarding party that investigates a basestar that is found disabled in space. She instructs others to place "SSR leads" in a pool of water as she attempts to access the basestar's computer database, hoping to make a data dump from the basestar to a Colonial data storage device.
Datapoints are either database records or specific subdatabases in the datastream. On New Caprica, Sharon Agathon tells the resistance that the datapoints indicated that the launch keys she retrieved were not damaged. Some time later, on a disabled basestar, she attempts to access the basestar's datastream and finds its datapoints severely corroded, suggesting that the datastream (and datapoints) have an organic element that is as equally susceptible to viral damage as the humanoid Cylons.
After living humanoid Cylons are found and information on the ship's infection is discovered, the boarding team appears to abort their information gathering attempt (A Measure of Salvation).
When a team of Colonials including Sharon Agathon and a Leoben prisoner boarded the Rebel Basestar, Agathon connected to the datastream to learn about what shape the ship was in and what they needed to do to repair the FTL drives. The datastream apparently showed her what she needed to know and she was able to come up with a way to use the Raptor they arrived on to patch the FTL drive so they could escape. Samuel Anders, who had recently learned of his true nature as a Final Five Cylon, reached for the datastream to see what effect it would have if he interacted with it. He never got the chance to see what effects it would have as Starbuck interupted him to get his help, but given the Five's interaction with the datastream in Anders' Hybrid tank in Daybreak, it probably would have been the same as any other Cylon that interacted with the datastream (Faith).
When the rebel Hybrid panicked and repeatedly jumped the ship, a Number Eight copy was apparently able to gain some insight into what happened by entering the datastream in the Hybrid's chamber. She wasn't able to determine what caused the Hybrid to panic, but determined that that was the reason for the jumping and determined that they seemed to be following the jumps of the Resurrection Hub and would thus still get the chance to complete their mission. Later, after D'Anna Biers was unboxed and resurrected by Cavil and Boomer, Boomer interacted with the datastream and detected the arrival of the rebel baseship and was confused as it was unscheduled, not realizing exactly which basestar it was at the time. Using the datastream, Boomer was apparently able to tap into the Hub's sensors and detected the Heavy Raider and Viper attack force which caused her to realize that it was the Rebel Basestar and that it was about to launch an attack to destroy the hub which frightened Cavil (The Hub).
When a Cylon is resurrected, they apparently end up in a datastream given that when Ellen Tigh was resurrected after her husband killed her, she was shown in what seemed to be a datastream before she finally downloaded into a new body and resurrected (No Exit).
During the Battle of The Colony, the Final Five use the datastream in Anders' Hybrid tank to combine the parts of resurrection technology they each posses and transmit it to The Colony. It works at first, but apparently as a result of connecting to the datastream like that, a side-effect is that everything about each of the Five is exposed to each other and they each see flashes of each other's memories. It's through this that Galen Tyrol finally learns the truth of his wife's death from Tory Foster's memories: she murdered her to protect her secret and in a rage, Tyrol breaks the link and kills Tory by snapping her neck. Breaking the link causes pain for the Hybrids recieving the data, but doesn't seem to cause the Five any discomfort aside from their shock at what the memory revealed (Daybreak, Part II).