Which window type is time-based, fixed size, with overlapping windows?

Which window type is time-based, fixed size, with overlapping windows?

• A. Tumbling Window
• B. Sliding Window
• C. Session Window
• D. Hopping Window

Answer: (D)

Understanding how fixed-duration, time-based windows can overlap is what this question is testing. A fixed-size window means every window covers the same amount of time. Overlap occurs when new windows start before the previous ones finish, which happens if the interval between starts (the hop) is shorter than the window length. A hopping window defines windows of a fixed duration and starts new ones at regular intervals. If you set the hop to be smaller than the window length, you get overlapping windows because multiple windows cover the same time periods. For example, with a 5-minute window and a 2-minute hop, you’d have windows like 0–5, 2–7, 4–9, and so on. This exact pattern—time-based, fixed-size windows that overlap due to periodic starts—matches the description. Tumbling windows are fixed-size but non-overlapping because each window starts right after the previous one ends. Session windows aren’t fixed in size; they depend on gaps between events. Sliding windows are also time-based and fixed-size with overlap, but the standard term emphasizing this periodic start leading to overlap is hopping window, which is why this is the best fit.

Understanding how fixed-duration, time-based windows can overlap is what this question is testing. A fixed-size window means every window covers the same amount of time. Overlap occurs when new windows start before the previous ones finish, which happens if the interval between starts (the hop) is shorter than the window length.

A hopping window defines windows of a fixed duration and starts new ones at regular intervals. If you set the hop to be smaller than the window length, you get overlapping windows because multiple windows cover the same time periods. For example, with a 5-minute window and a 2-minute hop, you’d have windows like 0–5, 2–7, 4–9, and so on. This exact pattern—time-based, fixed-size windows that overlap due to periodic starts—matches the description.

Tumbling windows are fixed-size but non-overlapping because each window starts right after the previous one ends. Session windows aren’t fixed in size; they depend on gaps between events. Sliding windows are also time-based and fixed-size with overlap, but the standard term emphasizing this periodic start leading to overlap is hopping window, which is why this is the best fit.