Memory
How memories are stored, decayed, and retrieved.
iCog's memory is a four-level living model on top of pgvector + Postgres:
- Static — facts that don't decay (names, birthdates)
- Dynamic — facts with recency-weighted relevance (preferences)
- Emergent — patterns synthesised from raw observations
- Meta — facts about facts (provenance, confidence)
Each memory has a type: semantic (facts), episodic (events),
procedural (how-tos), foundational (identity).
Three-layer ocean
Recall ranks across three depth layers:
- Surface — recent + high-confidence
- Middle — older but topically relevant
- Deep — rarely-accessed but potentially load-bearing
Reciprocal Rank Fusion combines HNSW (semantic) and BM25 (lexical) hits per layer, then reranks across layers.
Decay
Ebbinghaus-curve decay is applied at recall time, not at write time —
nothing is destroyed unless a forget is explicit. Dream consolidation
can promote heavily-accessed dynamic memories to static.