emem 0.2.1

Hybrid graph-based spatio-temporal memory system for embodied agents

Part of the EMOS ecosystem

Embodied Memory for Situated Agents

A hybrid graph-based spatio-temporal memory system that gives embodied agents the ability to remember what they observed, where they observed it, and when.

EMOS Documentation | Discord

Installation · Quick Start · Architecture · LLM Tools · API · Harness

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Why eMEM?

eMEM gives Physical AI agents a persistent, queryable sense of place and history, so they don't just react to the current frame, but remember, recall, and reason over everything they've observed.

Mobile robots and embodied AI agents accumulate thousands of observations per session; object detections, scene descriptions, sensor readings, but existing memory systems force a choice: vector databases that discard spatial structure, or metric maps that discard semantics. eMEM unifies both.

Capability	eMEM
Semantic search (meaning)	HNSW approximate nearest neighbor
Spatial queries (where)	R-tree range and nearest-neighbor
Temporal queries (when)	SQLite indexed timestamps
Episode structure	Graph edges with hierarchical sub-tasks
Memory consolidation	Automatic gist generation + tiered archival
LLM integration	10 ready-to-use tool definitions

Everything runs fully embedded, SQLite, hnswlib, and Rtree, with zero external services. A single .db file and a .hnsw.bin file contain the entire memory state.

eMEM is the memory layer of the EMOS (Embodied Operating System) ecosystem.

Installation

pip install emem

For semantic search with automatic embedding generation:

pip install emem[embeddings]  # adds sentence-transformers

Requirements: Python >= 3.8

Quick Start

from emem import SpatioTemporalMemory

with SpatioTemporalMemory(db_path="robot_memory.db") as mem:

    # Record observations with spatial coordinates
    mem.start_episode("kitchen_patrol")
    mem.add("Red chair near the dining table", x=10.0, y=10.0)
    mem.add("Cat sleeping on the chair",       x=10.2, y=10.1)
    mem.add("Coffee machine next to the sink", x=11.5, y=9.0)
    mem.end_episode()  # auto-consolidates into a gist, archives raw observations

    # Query by meaning -- searches both recent observations and consolidated summaries
    print(mem.semantic_search("furniture"))

    # Query by location
    print(mem.spatial_query(x=10.0, y=10.0, radius=3.0))

    # Query by time
    print(mem.temporal_query(last_n_minutes=30))

    # Situational awareness: nearby objects + area summaries + recent activity
    print(mem.get_current_context())

Architecture

eMEM is built around three complementary index structures that share a unified node/edge graph:

                    +-----------------+
                    | SpatioTemporal  |
                    |     Memory      |  <-- High-level facade
                    +--------+--------+
                             |
              +--------------+--------------+
              |              |              |
     +--------+--+   +------+------+  +----+-------+
     |  Working   |  |   Memory    |  | Consolida- |
     |  Memory    |  |   Tools     |  | tion       |
     |  (buffer)  |  | (10 tools)  |  | Engine     |
     +--------+---+  +------+------+  +----+-------+
              |              |              |
              +--------------+--------------+
                             |
                    +--------+--------+
                    |   MemoryStore   |
                    +--------+--------+
                             |
              +--------------+--------------+
              |              |              |
        +-----+----+  +-----+-----+  +----+-----+
        |  SQLite   |  |  hnswlib  |  |  R-tree  |
        | (nodes,   |  | (vector   |  | (spatial |
        |  edges,   |  |  search)  |  |  index)  |
        |  tiers)   |  |           |  |          |
        +-----------+  +-----------+  +----------+

Memory Graph

The memory is structured as a typed graph with four node types and six edge types:

Nodes:

• ObservationNode -- A single perception event: text, coordinates, timestamp, layer, confidence
• EpisodeNode -- A task or activity span grouping related observations
• GistNode -- A consolidated summary of multiple observations, with spatial extent and time range
• EntityNode -- A persistent tracked object/landmark with auto-merge by semantic similarity + spatial proximity

Edges:

• BELONGS_TO -- Observation → Episode
• FOLLOWS -- Episode → Episode (temporal sequence)
• SUBTASK_OF -- Episode → Episode (hierarchical nesting)
• SUMMARIZES -- Gist → Observation(s)
• OBSERVED_IN -- Entity → Observation (entity was seen in this observation)
• COOCCURS_WITH -- Entity ↔ Entity (entities observed together)

Memory Tiers

Observations flow through four tiers, inspired by human memory consolidation:

 working  -->  short_term  -->  long_term  -->  archived
 (buffer)     (in store)      (promoted)      (text dropped,
                                               gist remains)

When an episode ends, its observations are automatically consolidated into a GistNode that preserves the semantic content, spatial center, and time span. The raw observations are archived (text and embeddings removed) to bound storage growth while keeping the gist searchable.

Unified Search

semantic_search transparently queries both the observation and gist indexes through a single HNSW lookup. After consolidation, knowledge is not lost -- it is compressed into gists that remain fully searchable alongside recent observations.

LLM Tool Interface

eMEM provides 10 tools designed for LLM function-calling. Each returns a token-efficient formatted string.

Tool	Description
semantic_search	Search by meaning across observations and consolidated summaries
spatial_query	Find observations within a radius of a point
temporal_query	Find observations in a time range, chronologically ordered
episode_summary	Get summary of one or more episodes
get_current_context	Situational awareness: nearby objects, area summaries, recent activity
search_gists	Search only consolidated long-term memory
entity_query	Find known entities (objects, people, landmarks) by name, type, or location
locate	Resolve a concept to a spatial position (returns centroid + radius)
recall	Recall everything known about a concept (cross-layer observations, gists, entities)
body_status	Get latest body/internal state readings (battery, temperature, joint health)

Using with an LLM Agent

from emem import SpatioTemporalMemory

mem = SpatioTemporalMemory(db_path="agent.db")

# Get tool definitions (OpenAI function-calling format)
tools = mem.get_tool_definitions()

# Dispatch a tool call from the LLM
result = mem.dispatch_tool_call("semantic_search", {"query": "red chair"})

# Or call tools directly
result = mem.semantic_search("red chair", n_results=5, layer="vlm")

Relative Time Queries

Time parameters accept human-readable relative strings:

mem.temporal_query(time_after="-10m")    # last 10 minutes
mem.temporal_query(time_after="-2h")     # last 2 hours
mem.semantic_search("door", time_after="-1d")  # last 24 hours

API Reference

SpatioTemporalMemory

The primary interface. Manages ingestion, episodes, consolidation, and queries through a single object.

SpatioTemporalMemory(
    db_path="memory.db",           # SQLite database path
    config=None,                   # SpatioTemporalMemoryConfig (optional)
    embedding_provider=None,       # EmbeddingProvider (optional, enables semantic search)
    llm_client=None,               # LLMClient for gist generation (optional)
    get_current_time=None,         # Custom clock (optional)
)

Ingestion:

mem.add(text, x, y, z=0.0, layer_name="default", source_type="manual",
        confidence=1.0, metadata=None, embedding=None) -> str  # returns observation ID

Episodes:

mem.start_episode(name, metadata=None, parent_episode_id=None) -> str
mem.end_episode(consolidate=True) -> Optional[str]

Queries (all return formatted strings):

mem.semantic_search(query, n_results=5, layer=None, ...)
mem.spatial_query(x, y, radius=2.0, layer=None, ...)
mem.temporal_query(time_after=None, last_n_minutes=None, ...)
mem.episode_summary(episode_id=None, task_name=None, last_n=1)
mem.get_current_context(radius=3.0, include_recent_minutes=5.0)
mem.search_gists(query, n_results=5, ...)
mem.entity_query(name=None, entity_type=None, near_x=None, ...)
mem.locate(concept, n_results=10, ...)
mem.recall(query, n_results=10, ...)
mem.body_status(layers=None)
mem.add_body_state(text, layer_name, timestamp=None, confidence=1.0, metadata=None)

Embedding Providers

eMEM uses a protocol-based embedding interface. Bring your own or use the built-in providers:

from emem.embeddings import SentenceTransformerProvider

mem = SpatioTemporalMemory(
    db_path="memory.db",
    embedding_provider=SentenceTransformerProvider("all-MiniLM-L6-v2"),
)

Custom providers implement the EmbeddingProvider protocol:

class MyEmbedder:
    @property
    def dim(self) -> int:
        return 768

    def embed(self, texts: list[str]) -> np.ndarray:
        # Return (N, dim) float32 array
        ...

Consolidation

Automatic: end_episode() consolidates all episode observations into a gist and archives them.

Manual: For non-episodic observations that age past the consolidation window:

gist_ids = mem.consolidate_time_window()

Time-window consolidation uses DBSCAN to spatially cluster old observations before summarizing each cluster.

Configuration

from emem import SpatioTemporalMemoryConfig

config = SpatioTemporalMemoryConfig(
    db_path="memory.db",
    hnsw_path="memory_hnsw.bin",
    embedding_dim=384,

    # Working memory
    working_memory_size=50,        # max buffered observations
    flush_interval=2.0,            # seconds between auto-flushes
    flush_batch_size=5,            # flush after N observations

    # Consolidation
    consolidation_window=1800.0,   # 30 min before time-window consolidation
    consolidation_spatial_eps=3.0, # DBSCAN eps (meters)
    consolidation_min_samples=3,   # min cluster size

    # HNSW tuning
    hnsw_ef_construction=200,
    hnsw_m=16,
    hnsw_ef_search=50,
    hnsw_max_elements=100_000,
)

Observation Layers

Observations can be tagged with a layer_name to separate different perception modalities:

mem.add("Person detected", x=5.0, y=5.0, layer_name="detections", confidence=0.92)
mem.add("A kitchen with modern appliances", x=5.0, y=5.0, layer_name="vlm")
mem.add("Temperature: 22.5C", x=5.0, y=5.0, layer_name="sensors")

# Query specific layers
mem.semantic_search("person", layer="detections")
mem.spatial_query(x=5.0, y=5.0, radius=3.0, layer="vlm")

Body State / Interoception

eMEM treats internal body state (battery, temperature, joint health) as a first-class memory dimension alongside world observations:

# Record body state — automatically stamped at the robot's current position
mem.add_body_state("battery: 45%", layer_name="battery")
mem.add_body_state("72C across 4 cores", layer_name="cpu_temp")
mem.add_body_state("all joints nominal", layer_name="joint_health")

# Get latest body state
print(mem.body_status())
# Body Status:
#   [battery] battery: 45% (2min ago)
#   [cpu_temp] 72C across 4 cores (30s ago)
#   [joint_health] all joints nominal (5min ago)

# Body state is automatically included in get_current_context()
print(mem.get_current_context())

# Spatial-interoceptive associations emerge naturally:
# spatial_query near a steep ramp surfaces both terrain and battery observations
mem.spatial_query(x=10.0, y=10.0, radius=3.0)

Body state observations flow through the standard ObservationNode pipeline — they participate in episodes, consolidation, and all query tools. The key design decisions:

• No new node types: body state uses ObservationNode with source_type="interoception"
• Position-stamped: body observations inherit the robot's current position
• Position-preserving: body observations do NOT update the robot's tracked position
• Peer layers: "battery", "cpu_temp" etc. are regular layer names alongside "vlm", "detections"

Examples

See the examples/ directory:

• basic_memory.py -- Standalone usage: adding observations, episode lifecycle, all query tools
• memory_agent.py -- Simulated LLM agent using memory tools in a ReAct-style loop

Testing Harness

The harness/ directory contains a standalone test client that simulates what EMOS will do: an agent navigates a MiniGrid environment, a VLM describes each frame, synthetic body state is generated, and everything flows into eMEM for storage and querying. A ReAct agent then answers questions against the populated memory.

Setup

# Install harness dependencies (not part of emem itself)
pip install minigrid gymnasium

# Pull Ollama models
ollama pull nomic-embed-text-v2-moe:latest
ollama pull qwen3.5:latest

Running

# Quick smoke test (20 steps, VLM every 10)
python -m harness.run --steps 20 --vlm-every 10

# Full run (100 steps, VLM every 5)
python -m harness.run --steps 100 --vlm-every 5

# Keep the memory DB for later inspection
python -m harness.run --steps 50 --db-path my_test.db

# JSON output
python -m harness.run --steps 50 --json

# Verbose logging (debug level)
python -m harness.run --steps 20 -v

The harness logs progress to stderr as it runs: each VLM inference, episode boundaries, and each evaluation query with its result.

What it does

Each run:

1. Ingestion -- navigates MiniGrid with random actions, periodically sends rendered frames to a VLM (qwen3.5:latest) with two prompts (scene description + place type), and feeds results into eMEM as separate observation layers. Synthetic body state (battery, CPU temp, joint health) is generated every step.

2. Evaluation -- a ReAct agent answers 8 benchmark queries ("What places have I visited?", "What's my battery level?", "Where is the door?", etc.) and the harness measures tool selection accuracy, answer relevance, and latency.

Using from Python

from emem import SpatioTemporalMemory
from harness.providers import OllamaEmbeddingProvider, OllamaLLMClient, OllamaVLM
from harness.environments import MiniGridAdapter, SyntheticInteroception
from harness.agent import ReactAgent

embedder = OllamaEmbeddingProvider()
llm = OllamaLLMClient()
vlm = OllamaVLM()
env = MiniGridAdapter()
intero = SyntheticInteroception()

with SpatioTemporalMemory(
    db_path="my_test.db", embedding_provider=embedder, llm_client=llm,
) as mem:
    mem.start_episode("exploration")
    frame, pos = env.reset()

    for step in range(50):
        frame, pos, reward, done, info = env.step(2)  # forward

        if step % 5 == 0:
            desc = vlm.describe(frame, "Describe what you see in 1-2 sentences.")
            mem.add(desc, x=float(pos[0]), y=float(pos[1]), layer_name="description")

        for layer, text in intero.step().items():
            mem.add_body_state(text, layer_name=layer)

        if done:
            mem.end_episode()
            mem.start_episode("exploration")
            frame, pos = env.reset()

    mem.end_episode()

    # Query directly
    print(mem.semantic_search("door"))
    print(mem.body_status())

    # Or through the ReAct agent
    agent = ReactAgent(mem)
    print(agent.run("What places have I visited?").answer)

env.close()

Academic Benchmarks

The harness/benchmarks/academic/ module provides replay-based evaluation on established academic benchmarks for quantitative comparison. Unlike the live harness above, these load pre-recorded trajectories, ingest them into eMEM, answer dataset questions via a ReAct agent, and score against ground truth.

Supported Benchmarks

Benchmark	Venue	Questions	Focus	Scorer
LoCoMo	ACL 2024	1,986 conversational QA	Temporal reasoning, multi-hop recall	Token F1 + BLEU-1
eMEM-Bench (ours)	—	492 embodied QA across 12 AI2-THOR scenes	Spatial, temporal, entity, episodic, interoceptive recall	LLM judge (1-5)

Ablation Study

Five configurations isolate the contribution of each eMEM component:

Ablation	What it removes
full	Nothing (baseline)
vector_only	All tools except semantic_search
no_spatial	spatial_query, locate, recall tools
no_consolidation	Gist generation and archival
flat_layer	Multi-layer support (all observations use layer_name="default")

Running Benchmarks

# LoCoMo (text-only conversational memory)
python -m harness.run_benchmark \
  --dataset locomo --data-dir ./data/locomo \
  --max-samples 3 --ablation full

# eMEM-Bench (embodied QA over AI2-THOR scenes)
python -m harness.run_benchmark \
  --dataset emem_bench --data-dir ./data/emem_bench \
  --ablation full

# Full ablation sweep with JSON output
python -m harness.run_benchmark \
  --dataset locomo --data-dir ./data/locomo \
  --ablation full,vector_only,no_spatial,no_consolidation,flat_layer \
  --json > results/locomo_ablation.json

# Use Gemini provider instead of Ollama
python -m harness.run_benchmark \
  --dataset locomo --data-dir ./data/locomo \
  --provider gemini --embed-model text-embedding-004 \
  --llm-model gemini-2.0-flash-lite

CLI Options

--dataset         locomo | emem_bench
--data-dir        Path to dataset directory
--ablation        Comma-separated ablation names (default: full)
--max-samples     Limit number of samples evaluated
--provider        ollama | gemini (default: ollama)
--embed-model     Embedding model (default: nomic-embed-text-v2-moe:latest)
--llm-model       LLM for agent + consolidation (default: qwen3.5:latest)
--json            Output JSON report instead of formatted tables
-v                Verbose logging

Data Directory Layouts

LoCoMo:

data/locomo/
  locomo.json   # array of conversations with sessions + qa_pairs

eMEM-Bench:

data/emem_bench/
  scenes/{scene_id}/trajectory.json
  scenes/{scene_id}/questions.json

Development

git clone https://github.com/Automatika-Robotics/eMEM.git
cd eMEM
python -m venv .venv && source .venv/bin/activate
pip install -e ".[dev]"
pytest tests/ -v

Part of the EMOS Ecosystem

eMEM is the memory layer of EMOS (Embodied Operating System) — the unified orchestration layer for Physical AI. Alongside its sibling components:

• EmbodiedAgents — Intelligence and manipulation. ML model graphs with semantic routing and adaptive reconfiguration.
• Kompass — Navigation. GPU-accelerated planning and control.
• Sugarcoat — Lifecycle management. Event-driven system design for ROS 2.
• eMEM — Memory. Spatio-temporal recall for situated agents.

Write a recipe once. Deploy it on any robot. No code changes.

Resources

• EMOS Documentation — Tutorials, recipes, and usage guides
• Discord — Community and support

License

All rights reserved. Copyright (c) 2024 Automatika Robotics.