Memory Survey: A Unified Taxonomy (Dec 2025)
A comprehensive survey paper from December 2025 proposed a unified taxonomy for agent memory systems, organizing the landscape along three dimensions: forms, functions, and dynamics.
Three Dimensions
1. Memory Forms (What is stored)
- Parametric Memory - Knowledge encoded in model weights during training.
- Textual Memory - Natural language stored in external systems (our primary focus).
- Embedding Memory - Dense vector representations for semantic search.
- Structured Memory - Knowledge graphs, databases, and tables.
2. Memory Functions (How it is used)
- Episodic - Event sequences and experiences (session logs, conversation history).
- Semantic - Facts, concepts, and general knowledge (extracted insights).
- Procedural - Skills, workflows, and tool-use patterns (how-to knowledge).
3. Memory Dynamics (How it changes)
- Accumulation - Adding new memories over time.
- Consolidation - Merging, summarizing, and compressing memories.
- Forgetting - Decay, pruning, and active deletion of stale memories.
- Retrieval-induced modification - Memories change when accessed (confidence updates, access counts).
Key Findings
- Most systems only implement accumulation - Few handle consolidation or forgetting well.
- Retrieval quality matters more than storage capacity - Better retrieval beats more memory.
- Memory safety is under-studied - Poisoning, hallucination reinforcement, and privacy are open problems.
- Evaluation is inconsistent - No standard benchmarks across all memory types.
Design Principles from the Survey
- Treat memory as a runtime policy problem, not just a storage problem.
- Budget-aware routing: choose retrieval complexity per query.
- Hierarchical retrieval: theme -> episode -> raw evidence.
- Active forgetting: use decay and reinforcement to control growth.
- Memory safety: treat poisoning and self-reinforcing bad memory as threats.
Relevance to Memory Platform
The taxonomy maps directly to our system:
| Survey Concept | Platform Feature |
|---|---|
| Textual + Structured Memory | Postgres memories with JSON context |
| Episodic Function | Sessions + session-scoped memories |
| Semantic Function | Project memories with categories |
| Procedural Function | Pattern/procedure category memories |
| Accumulation | Memory creation via API/MCP |
| Consolidation | Memory evolution (merge/compress) |
| Forgetting | Confidence decay + access tracking |
References
- "A Survey on Memory Systems for LLM-based Agents" (Dec 2025)
- The survey covers 100+ papers from 2023-2025
- Proposed evaluation framework for memory systems