The 17.19 Substantial Similarity-Extrinsic Test; Intrinsic Test is a two-part test used to determine whether a work is substantially similar to another work. The Extrinsic Test is a comparison of the works' external elements, like plot, characters, themes, dialogue, and setting. The Intrinsic Test is a comparison of the works' internal elements, like style, mood, and pace. Both tests are used to determine if the works are similar enough to be considered a copyright infringement. There are two main types of 17.19 Substantial Similarity-Extrinsic Test; Intrinsic Test: the Abstraction-Filtration-Comparison Test and the Ordinary Observer Test. The Abstraction-Filtration-Comparison Test is a three-step process that filters out unprotected elements of the works and then compares the remaining protected elements to determine if the works are substantially similar. The Ordinary Observer Test evaluates the works as a whole and determines if an ordinary observer would find the works to be substantially similar.