brainy/docs/DATA_MODEL.md

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Data Model

How Brainy stores entities and relationships, and the critical distinction between data and metadata.


Entity (Noun)

An entity is the fundamental data unit in Brainy. Every entity has:

Field Type Indexed Description
id string Primary key UUID v4 (auto-generated or custom)
data any HNSW vector index Content used for semantic/hybrid search. Strings auto-embed.
metadata object MetadataIndex Structured queryable fields (tags, dates, flags, etc.)
type NounType MetadataIndex (as noun) Entity type classification
vector number[] HNSW 384-dim embedding (auto-computed from data or user-provided)
confidence number MetadataIndex Type classification confidence (0-1)
weight number MetadataIndex Entity importance/salience (0-1)
service string MetadataIndex Multi-tenancy identifier
createdAt number MetadataIndex Creation timestamp (ms since epoch)
updatedAt number MetadataIndex Last update timestamp (ms since epoch)
createdBy object MetadataIndex Source augmentation info

Example

const id = await brain.add({
  data: 'John Smith is a software engineer at Acme Corp',  // → embedded into vector
  type: NounType.Person,
  metadata: {                   // → indexed, queryable via where filters
    role: 'engineer',
    department: 'backend',
    yearsExperience: 8
  },
  confidence: 0.95,
  weight: 0.7
})

Relationship (Verb)

A relationship is a typed, directed edge connecting two entities.

Field Type Indexed Description
id string Primary key UUID v4 (auto-generated)
from string GraphAdjacencyIndex Source entity ID
to string GraphAdjacencyIndex Target entity ID
type VerbType GraphAdjacencyIndex (as verb) Relationship type classification
data any Opaque content (overrides auto-computed vector if provided)
metadata object Structured fields on the edge
weight number Connection strength (0-1, default: 1.0)
confidence number Relationship certainty (0-1)
evidence RelationEvidence Why this relationship was detected
createdAt number Creation timestamp (ms since epoch)
updatedAt number Last update timestamp (ms since epoch)
service string Multi-tenancy identifier

Example

const relId = await brain.relate({
  from: personId,
  to: projectId,
  type: VerbType.WorksOn,
  data: 'Lead engineer on the AI module',   // Optional: content for this edge
  metadata: {                                // Optional: queryable edge fields
    role: 'lead',
    startDate: '2024-01-15'
  },
  weight: 0.9
})

Data vs Metadata

This is the most important concept in Brainy's storage model:

  • Embedded into a 384-dimensional vector via the WASM embedding engine
  • Searchable via semantic similarity (HNSW vector index) and hybrid text+semantic search
  • Queried by passing query to find():
    brain.find({ query: 'machine learning algorithms' })
    
  • NOT indexed by MetadataIndex — you cannot use where filters on data
  • Stored opaquely: strings, objects, numbers — anything goes

metadata — Structured Queryable Fields

  • Indexed by MetadataIndex with O(1) lookups per field
  • Queryable via where filters using BFO operators:
    brain.find({
      where: {
        department: 'engineering',
        yearsExperience: { greaterThan: 5 },
        tags: { contains: 'senior' }
      }
    })
    
  • NOT used for vector/semantic search
  • Must be a flat or lightly nested object

Quick Reference

data metadata
Purpose Content for embedding / semantic search Structured fields for filtering
Searched by find({ query }) — vector similarity, hybrid text+semantic find({ where }) — exact, range, set operators
Indexed by HNSW vector index MetadataIndex
Queryable with operators? No Yes (equals, greaterThan, oneOf, etc.)
Auto-embedded? Yes (strings → 384-dim vectors) No
Typical content Text descriptions, document content Tags, dates, status flags, categories, numeric fields

Common Pattern

// Add an article
await brain.add({
  data: 'A deep dive into transformer architectures and attention mechanisms',
  type: NounType.Document,
  metadata: {
    title: 'Transformer Deep Dive',
    author: 'Dr. Chen',
    publishedYear: 2024,
    tags: ['AI', 'transformers', 'NLP'],
    status: 'published'
  }
})

// Search by content (semantic — searches data)
const results = await brain.find({ query: 'neural network attention' })

// Filter by fields (exact — queries metadata)
const recent = await brain.find({
  where: {
    publishedYear: { greaterThan: 2023 },
    status: 'published'
  }
})

// Combine both (Triple Intelligence)
const precise = await brain.find({
  query: 'attention mechanisms',             // Semantic search on data
  where: { author: 'Dr. Chen' },            // Metadata filter
  connected: { from: authorId, depth: 1 }   // Graph traversal
})

Storage Field Naming

Internally, Brainy uses different field names in storage vs the public API:

Public API (Entity/Relation) Storage (metadata object) Notes
type noun Entity type stored as noun
from sourceId Relationship source
to targetId Relationship target
type (on Relation) verb Relationship type stored as verb

When querying with find(), you can use:

  • type parameter (convenience alias, equivalent to where.noun)
  • where.noun directly
// These are equivalent:
brain.find({ type: NounType.Person })
brain.find({ where: { noun: NounType.Person } })

Standard Metadata Fields

When you add an entity, Brainy stores these standard fields in the metadata object alongside your custom fields:

Field Set By Description
noun System Entity type (NounType enum value)
subtype User Per-NounType sub-classification (e.g. 'employee', 'invoice', 'milestone'). Flat string, no hierarchy. Indexed on the fast path and rolled into per-NounType statistics.
data System The raw data value (stored opaquely)
createdAt System Creation timestamp
updatedAt System Last update timestamp
confidence User Type classification confidence
weight User Entity importance
service User Multi-tenancy identifier
createdBy User/System Source augmentation

On read, these standard fields are extracted to top-level Entity properties. The metadata field on the returned Entity contains only your custom fields.

Subtype — sub-classification within a NounType

type (NounType) is a stable 42-value enum. subtype is the consumer-chosen string vocabulary within a type:

// A Person who is an employee:
await brain.add({
  data: 'Avery Brooks — runs the AI lab',
  type: NounType.Person,
  subtype: 'employee',
  metadata: { department: 'ai-lab' }
})

// A Document that is an invoice:
await brain.add({
  data: 'INV-2026-001',
  type: NounType.Document,
  subtype: 'invoice',
  metadata: { amount: 1500 }
})

subtype lives at the top level — NOT inside metadata, NOT inside data. That's how find({ type, subtype }) routes through the standard-field fast path (column-store hit) instead of the metadata fallback. See Subtypes & Facets for the full guide including trackField() and migrateField().

Subtype — sub-classification within a VerbType (7.30+)

Relationships are first-class citizens too. Every verb (VerbType) gets the same subtype primitive — a ReportsTo relationship might carry subtype: 'direct' vs 'dotted-line'; a RelatedTo edge might carry 'spouse' / 'sibling' / 'colleague'. Same shape as the noun side: flat string, no hierarchy, top-level standard field on HNSWVerbWithMetadata and on the public Relation<T>:

await brain.relate({
  from: ceoId,
  to: vpId,
  type: VerbType.ReportsTo,
  subtype: 'direct',                  // top-level standard field
  metadata: { since: '2025-Q1' }      // user-custom fields stay in metadata
})

Fast-path filter on the verb side:

const direct = await brain.related({
  from: ceoId,
  type: VerbType.ReportsTo,
  subtype: 'direct'
})

The verb-side rollup at _system/verb-subtype-statistics.json mirrors the noun-side _system/subtype-statistics.json — same shape, same self-heal machinery. Per-VerbType-per-subtype counts are O(1) via brain.counts.byRelationshipSubtype().

Verbs and nouns now have full capability parity — every API on the noun side has a verb-side mirror, including the new brain.updateRelation() (which closed a pre-7.30 gap where relationships had no update path).

Standard verb fields

The verb-side equivalent of STANDARD_ENTITY_FIELDS is STANDARD_VERB_FIELDS, exported from src/coreTypes.ts. Verb-specific standard fields:

Field Description
verb The VerbType enum value
sourceId / targetId The two endpoints of the relationship
subtype Sub-classification within the VerbType (7.30+)
confidence, weight, createdAt, updatedAt, service, createdBy, data Same semantics as the noun-side standard fields

The companion resolveVerbField(verb, field) helper resolves field paths the same way resolveEntityField does for nouns: standard fields first, metadata fallback for everything else.


See Also