NOMLViewer

NoSQL Schema Documentation

What is NOMLViewer?

NOMLViewer is a design document viewer for NoSQL database structures. It transforms YAML-based schema definitions into beautiful, readable documentation.

What is NOML?

NOML stands for NoSQL Modeling Language - a specification for describing NoSQL database schemas. It provides a standardized way to document NoSQL database structures using familiar YAML syntax.

Current Status

Firestore Only

Currently, NOMLViewer supports only Google Cloud Firestore. Support for other NoSQL databases (MongoDB, DynamoDB, etc.) is planned for future releases.

Lenient Parsing

NOMLViewer uses lenient parsing. Unknown or undefined parameters will be silently ignored (not rendered, no errors). This allows forward compatibility and custom extensions.

Vision

Visual Schema Builder: Build schema definitions through an intuitive UI without writing YAML manually, then export to YAML with one click
Firestore Code Generation: Auto-generate Firestore security rules, composite indexes (firestore.indexes.json), TypeScript type definitions, and seed data scripts from NOML schema
Multi-database support: MongoDB, DynamoDB, Cassandra, and more
Export features: Generate documentation in various formats (PDF, HTML)
Schema validation: Real-time validation rules and security rule generation
Team collaboration: Share schemas with your team
VS Code extension: Edit and preview NOML files directly in your editor

How to Use (Firestore)

1Create a NOML file

Create a YAML file with the following basic structure:

version: "0.1"
database: firestore
metadata:
  name: My App
  description: Description of your database schema

collections:
  # Define your collections here

2Define Collections

Add your Firestore collections with their fields:

collections:
  users:
    description: User accounts
    fields:
      email:
        type: string
        required: true
        description: User email address
        example: "user@example.com"
      displayName:
        type: string
        description: Display name
      createdAt:
        type: timestamp
        default: serverTimestamp

3Add Subcollections

Nest subcollections within parent collections:

collections:
  users:
    fields:
      email:
        type: string
        required: true

    subcollections:
      settings:
        description: User preferences
        fields:
          theme:
            type: string
            default: light
          notifications:
            type: boolean
            default: true

4Use References

Define relationships between collections using references:

collections:
  posts:
    description: Blog posts
    fields:
      title:
        type: string
        required: true
      authorRef:
        type: reference
        target: users  # Reference to users collection
        description: Author of the post

5Visualize

Paste your NOML schema into the viewer or drag & drop your YAML file to see the visualization.

YAML Schema Reference

Root Structure

Field	Required	Description
version	Yes	NOML version (e.g., "0.1")
database	Yes	Database type (currently only "firestore")
metadata	No	Project metadata (name, description, author)
enums	No	Reusable enum definitions
collections	Yes	Collection definitions

Enum Definition

Field	Required	Description
description	No	Enum description
values	Yes	Array of allowed values

Use the enum name directly as the field type:

enums:
  UserRole:
    description: User permission levels
    values: [user, admin, moderator]

collections:
  users:
    fields:
      role:
        type: UserRole  # enum名をtypeに指定
        default: user

Collection Definition

Field	Required	Description
description	No	Collection description
path	No	Firestore path pattern (e.g., "users/{userId}")
keys	No	Key definitions (primary, foreign, unique, compositeUnique)
fields	Yes	Field definitions
subcollections	No	Nested subcollection definitions
indexes	No	Composite index definitions (name, description, fields, order)
security	No	Security rules (read, create, update, delete)

Field Definition

Field	Required	Description
type	Yes	Field type (Firestore types or enum name)
description	No	Field description
required	No	Whether field is required (default: false)
nullable	No	Whether field can be null (distinguishes from optional)
default	No	Default value
example	No	Example value for documentation
source	No	Value source (e.g., "documentId")
immutable	No	Field cannot be updated after creation
autoUpdate	No	Auto-update on each write (for updatedAt)
validation	No	Validation rules (min, max, minLength, maxLength, format, pattern)
denormalizedFrom	No	Source of denormalized data (collection.field)
target	For reference	Target collection name for reference type
items	For array	Array item type definition (type)

Validation Rules

Both "validation" and "constraints" keys are supported for backwards compatibility.

Field	Description
min / max	Number constraints (min/max value)
minLength / maxLength	String length constraints
minItems / maxItems	Array item count constraints
format	Common formats: email, url, uuid
pattern	Regex pattern for validation
enum	Inline list of allowed values (use enums definition for reusability)

Complete Example

version: "1.0"
database: firestore
description: Sample Application Schema

enums:
  UserRole:
    description: User permission levels
    values:
      - value: user
        label: User
        description: Standard user
      - value: admin
        label: Administrator
      - value: moderator
        label: Moderator
  Status:
    values: [draft, published, archived]
    transitions:
      draft: [published]
      published: [archived]

collections:
  users:
    description: User accounts
    path: users/{userId}

    keys:
      primary: userId
      description: Document ID = Firebase Auth UID
      unique:
        - field: email
          enforceBy: firebaseAuth

    fields:
      userId:
        type: string
        required: true
        source: documentId
        description: User ID (Firebase Auth UID)

      email:
        type: string
        required: true
        description: Email address
        example: "user@example.com"
        validation:
          format: email

      name:
        type: string
        required: true
        description: Display name
        validation:
          minLength: 1
          maxLength: 50

      role:
        type: UserRole
        default: user
        description: Permission level

      createdAt:
        type: timestamp
        required: true
        immutable: true
        description: Account creation date

      updatedAt:
        type: timestamp
        required: true
        autoUpdate: true
        description: Last update date

    subcollections:
      settings:
        description: User preferences
        fields:
          theme:
            type: string
            default: light
          notifications:
            type: boolean
            default: true

    indexes:
      - name: users_by_role
        description: List users by role
        fields:
          - field: role
            order: asc
          - field: createdAt
            order: desc

  posts:
    description: Blog posts
    path: posts/{postId}

    keys:
      primary: postId
      foreign:
        - field: authorId
          references: users.userId
          onDelete: restrict

    fields:
      postId:
        type: string
        required: true
        source: documentId

      title:
        type: string
        required: true
        validation:
          maxLength: 100

      authorId:
        type: string
        required: true

      authorName:
        type: string
        required: true
        denormalizedFrom:
          collection: users
          field: name
          key: authorId

      status:
        type: Status
        default: draft

Firestore Field Types

Type	Description
string	Text data
number	Integer or float
boolean	True or false
timestamp	Date and time
geopoint	Geographic coordinates
reference	Document reference
array	Array of values
map	Nested object

Special Default Values

Value	Description
serverTimestamp	Auto-generated server timestamp
autoId	Auto-generated document ID

Ready to start?

Go to the viewer and try with the sample schema or your own NOML file.

Open Viewer