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This can include how scripts are used in programming - all programming scripts are shaping storylines in the way that all programming is shaping - but the term "storyline" is not programming-exclusive.
Storylines can come from absolutely anything and have any source. The abuser can make up a storyline completely from scratch, and some situations where systems are abused over roleplay that involves OCs would fall under that.
However, fictional media can be used as a storyline, too. This includes old fairy tales and media that the perpetrators or victim would have grown up with. However, it can also include media that is new during the time of the abuse, including if the abuse occurs when the victim is an adult. That's because absolutely anything can be used in abuse, and shaping isn't something that inherently has established methods that is passed around through or developed by organizations.
Other things that can serve as inspiration for storylines include history, lyrics of songs, events one knows about personally, philosophical stories or concepts, mythology, or basically anything that has a narrative in anyway.
This can include things like a story taking place inside the victim's headspace, with elements that the abuser has put there on purpose due to influencing the system's innerworld on purpose so they would know how it works and thus how to abuse the system.
However, a storyline can also be a narrative that an abuser wants someone to act out in their innerworld, or over roleplay with them or their system. This would be a narrative about abuse or where abuse is part of the end goal in telling it, e.g. using a roleplay to groom somebody's system, emphasizing a certain fictional story with a doomed ending to make them think a certain outcome for their system is inevitable so their innerworld reflects that, etc.
Not all shaping has a storyline. If shaping includes a storyline that is based on an existing narrative or piece of media, that externally-existing thing is called the storysource. However, if a storyline is purely made up for the shaping, it does not have a storysource.