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With Sliding Windows, a new window is defined when a new record enters on the right, or one after a record leaves the window on the left. In this example, a new window is formed with C as the end point when it enters the window area, creating a window with the unique set {A, B, C}. Then, as the window slides along, a new window is defined 1ms after a record, A, leaves the window, creating a new window with the unique set of {B, C}. The next window to be created in this example would be 1ms after B leaves the window, creating a window with just {C}. In this implementation, there are two ways to define a distinct window using the sliding window semantics, one when a record enters the window from the right (Figure 3), and one when a record leaves the window on the left (Figure 4). When the a record leaves the window, the next window is 1ms higher than that record's timestamp. 

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