Links

A link defines a relationship between objects, such as an invoice's customer. Use links when you need to navigate or query related objects; use properties for values that belong to one object.

Define a link

Add link(id, target, options?) to the source type's links array. This belongs in the Invoice definition from Object types:

import { link } from "@sixb/core/ontology"
import { Customer } from "./customer"

const links = [
  link("customer", Customer, { cardinality: "one" }),
]

Pass links to defineObjectType(). The ID names the relationship on the source type; the target defines which object type it can point to. Optional name and description provide display text.

Declaring a link does not create relationships between instances. Use object operations, action edits, or projections to populate them.

Choose cardinality

Cardinality applies to each source object, not to how many objects can point at a target:

A "one" link is not required; an object can have no target. Set cardinality explicitly to make the intended relationship clear.

Links have a direction. Declaring Invoice.customer does not add a separate Customer.invoices link. Use incoming traversal to find the invoices that point to a customer.

Add relationship properties

A link can hold values about the relationship itself. For example, an invoice can have several reviewers, each with their own assignment time:

import { link, prop } from "@sixb/core/ontology"
import { Customer } from "./customer"
import { Reviewer } from "./reviewer"

const links = [
  link("customer", Customer, { cardinality: "one" }),
  link("reviewers", Reviewer, {
    cardinality: "many",
    properties: [prop("assignedAt", "timestamp", { required: true })],
  }),
]

Define and export the Reviewer object type in ontology/ before using this relationship. Declare relationship properties with prop(), just like object properties. Sixb validates their values when you write a link. A link without a property definition cannot accept extra properties.

See Write relationship properties for the corresponding write.

Other targets

Prefer an imported object type for typed relationships. Use these forms when the model needs them:

link.ref() also accepts an array of target IDs. All named target types must be registered in the project. For typed queries through ID-based links, the CLI generates the required ontology types during development and builds.

Use a single target type when you want typed traversal.