Decay

Salience falling with age on a half-life, so that what has not been touched in a long time stops competing with what has.

Why it matters in a memory layer

Decay is what keeps a bounded store honest, and its rate is the most consequential tuning decision in forgetting: too fast and the system loses the user, too slow and nothing is ever displaced. The rate is not one number, though -- it has to be scaled by memory type, because what decays is relevance rather than truth. A uniform half-life applied to this course's corpus emptied retrieval entirely inside seventeen months.

Connections

Taught in: Decay and Memory Tiers

Used in: Forgetting Under a Budget