---
id: "concept-semantic-search"
type: "concept"
source_timestamps: ["00:13:35", "00:15:26"]
tags: ["data-retrieval", "machine-learning"]
related: ["concept-agent-web", "concept-open-brain"]
definition: "A retrieval method that uses vector embeddings to find data based on conceptual meaning and mathematical proximity, rather than exact keyword matches."
sources: ["s22-saas-replacement"]
sourceVaultSlug: "s22-saas-replacement"
originDay: 22
---
# Semantic Search via Vector Embeddings

## Definition

A retrieval method that uses vector embeddings to find data based on conceptual meaning and mathematical proximity, rather than exact keyword matches.

## How It Works in the Open Brain

1. **Embedding on capture.** When you log a thought (e.g. via [[entity-slack-d22]]), an edge function on [[entity-supabase-d22]] sends the text to an embedding model and gets back a high-dimensional vector.
2. **Storage.** The raw text, the extracted metadata, and the vector all land in [[entity-postgresql]] via [[entity-pgvector]].
3. **Embedding on query.** When you (or an agent through [[concept-model-context-protocol]]) ask a question, the question is also vectorized.
4. **Nearest-neighbor retrieval.** Postgres returns the rows whose vectors are mathematically closest to the query vector.

## Worked Example (from the talk)

If you log: *'My colleague is leaving her job to start a consulting business because she's unhappy with the reorg,'* an agent can later retrieve that note when you ask about **'career changes'** or **'people moving into product'** — even though none of those phrases appear in the original text. Keyword search (Control-F) would miss this entirely.

## Why This Kills the Folder

Semantic search is what makes a flat, folder-less database **infinitely more useful** for an AI agent than any hierarchical filing system. The agent does not need your ontology — it computes its own. This is the technical reason the [[concept-agent-web]] beats the Human Web for agent memory, and the substrate underneath [[claim-notion-evernote-obsolete]].