Selva

About

Selva is a realtime acyclic graph database.

It was built to handle massively scalable data structures with complex hierarchies and taxonomies, with real-time updates, transparent subscriptions, and powerful queries.

Documents or graph vertices can have any number or combination of parents and children. Field values can be augmented with data from other members of its hierarchy allowing for efficient inheritance of data.

Here are some of its features:

• Real-time engine and subscription model

• Schemas enforce data types with built-in validation

• Persistence layer using any s3 endpoint allowing backups every 5 minutes and access to all versions of the data available at all times

• JSON-based DSL for queries

• Optional indexes optimised for the graph data structure

• I18n and search included

• Client API uses web sockets to subscribe to data and transparently keep content updated in real-time

• Versioning system for the data allows branches of data to be merged and revised into the master data, allowing content creators to try changes before data is published to a live system

Documentation

Selva is composed of two main modules - @saulx/selva client and @saulx/selva-server. Documentation for its API as well as the two main concepts: the schemas and its query DSL can be viewed in the links below.

• API
• Schema definition
• Query language

Usage

First setup a Selva server.

import { start } from '@saulx/selva-server'

const server = await start({ port: 8080 })

Setup the client and load the schema

import { connect } from '@saulx/selva'

const client = connect({ port: 8080 })
await client.updateSchema({
  languages: ['en', 'nl'],
  types: {
    genre: {
      prefix: 'ge',
      fields: {
        name: { type: 'text' },
        icon: { type: 'string' },
      },
    },
    movie: {
      prefix: 'mo',
      fields: {
        title: { type: 'text' },
        year: { type: 'int', search: true },
        director: { type: 'string' },
        icon: { type: 'string' },
        technicalData: {
          type: 'object',
          properties: {
            runtime: { type: 'int' },
            color: { type: 'string' },
            aspectRatio: { type: 'string' },
          },
        },
      },
    },
    person: {
      prefix: 'pe',
      fields: {
        name: { type: 'string' },
        born: { type: 'int' },
        died: { type: 'int' },
      },
    },
  },
})

Set some data.

await Promise.all(
  [
    {
      $id: 'mo2001ASpaceOdyssey',
      title: {
        en: '2001: A Space Odyssey',
        nl: '2001: Een zwerftocht in de ruimte',
      },
      year: 1968,
      director: 'Stanley Kubrick',
      technicalData: {
        runtime: 149,
        color: 'true',
        aspectRatio: '2.20:1',
      },
    },
    {
      $id: 'moSoylentGreen',
      title: {
        en: 'Soylent Green',
        nl: 'Groen Rantsoen',
      },
      year: 1973,
      director: 'Richard Fleischer',
      technicalData: {
        runtime: 97,
        color: 'true',
        aspectRatio: '2.35:1',
      },
      children: ['peCharltonHeston', 'peLeighTaylorYoung', 'peChuckConnors'],
    },
    {
      $id: 'moMetropolis',
      title: { en: 'Metropolis' },
      year: 1927,
      director: 'Fritz Lang',
      technicalData: {
        runtime: 153,
        color: 'false',
        aspectRatio: '1.33:1',
      },
    },
  ].map((movie) => client.set(movie))
)

Query the data

const result = await client.get({
  $id: 'moSoylentGreen',
  $language: 'en',
  title: true,
  year: true,
  director: true,
})

Or subscribe to changes.

const obs = client.subscribe({
  $id: 'moSoylentGreen',
  $language: 'en',
  title: true,
  year: true,
  director: true,
})

const sub = obs.subscribe((data) => {
  // render the data
  // (will also be run one time when subscribing)
  console.log('Data changed: ', data)
})

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This project was funded through the NGI0 Discovery Fund, a fund established by NLnet with financial support from the European Commission's Next Generation Internet programme, under the aegis of DG Communications Networks, Content and Technology under grant agreement No 825322.