Neighbourhoods are essentially just Perspectives (graph databases) that are shared and synced between Agents.

Every Neighborhood needs to use a Link Language to decide what technology it uses to store the associations (links) between the Expressions.

Currently, there is one Link Language implemented called Perspective Diff Sync (opens in a new tab) based on Holochain:

const langs = await client.runtime.knownLinkLanguageTemplates();
console.log(langs[0]); // The uuid of the default Link Language

Creating a Neighborhood

As mentioned before, the Link Language is responsible for storing and synchronizing the links in a Neighborhood. If we want to avoid storing the links in the same location as everyone else following this guide, we should create a duplicate of the language. By giving it a unique ID, we can ensure that the links are saved in a new and private network:

const uniqueLinkLanguage = await ad4m.languages.applyTemplateAndPublish(
    uuid: "84a329-77384c-1510fb",
    name: "Perspective Diff Sync clone",

With that new Link Language, actually creating the Neighbourhood is simple. We just have to provide the ID of the perspective we want to upgrade to a Neighbourhood and the address of the Link Language:

const meta = new Perspective();
const neighbourhoodUrl = await ad4m.neighbourhood.publishFromPerspective(
console.log(neighbourhoodUrl); // => neighbourhood://Qm123456789abcdef

The meta field is a Perspective that is immutably stored with the Neighbourhood. It can hold arbitrary meta information about the Neighbourhood but can technically stay empty, just like we did here.

Joining a Neighborhood

Assume everything above happened on Alice's agent. Alice now shares the Neighbourhood's URL with Bob. This is what Bob does to join the Neigbourhood:

const { uuid } = await ad4m.neighbourhood.joinFromUrl(neighbourhoodUrl);
const sharedNotes = await ad4m.perspective.byUUID(uuid);

Now Bob can read what used to be Alice's private notes:

const links = await sharedNotes.get(
  new LinkQuery({
    predicate: "sioc://likes",
links.forEach(async (link) => {
  const { data: who } = await ad4m.expression.get(link.source);
  const { data: what } = await ad4m.expression.get(;
  console.log(who, "likes", what);