Data model

The core data model in VisuallyJs is that of a graph, as discussed here on Wikipedia.

A graph is a collection of nodes, groups, edges and ports.

Nodes map to entities in your data model.
Groups are collections of nodes/groups. They map to entities in your data model.
Ports are logical and/or physical locations on nodes/groups that are the terminus for an edge. Not all apps use ports in their data model. The simplest example of the usage of ports is perhaps a database schema: you'd represent your tables as nodes, and then the columns on each table would be represented as ports. Another good analogy is ports in TCP/IP.
Edges are relationships between nodes, groups or ports.

tip

In the VisuallyJs documentation you'll see references to Vertex and vertices - this is a node, port or group. We often use "vertex" to refer to the source and target terminus for an edge throughout the documentation as it's easier than typing "Node/Group/Port"...and also, conceptually, its correct!

What do I need the model for?

A brief list of the sorts of things you can do with the model:

add/remove/update nodes, groups and edges
undo/redo operations
impose constraints on connectivity between objects
specify object factories for the creation of new objects
import/export the dataset
execute multiple operations within a transaction
select specific contents via filtering
check for the existence of and retrieve paths between vertices

Changes to the model are automatically reflected in the UI.

Accessing the model

You'll need to access the model from inside your code in order to use the programmatic model API. Expand the section below for instructions on how to do that.

How to access the model

Data Format

The various parts of your data model can be represented as any valid Javascript type. As an example, here is the backing data for the Book table in the Schema Builder starter app:

{
  "id":"book",
  "name":"Book",
  "type":"table",
  "columns":[
    { "id":"123", "name":"id", "datatype":"integer", "primaryKey":true },
    { "id":"456", "name":"isbn", "datatype":"varchar" },
    { "id":"789", "name":"title", "datatype":"varchar" }
  ]
}

Object IDs

Every vertex is required to have a unique ID. VisuallyJs attempts to derive this automatically from your data, by looking for an id member, which should be a string.

tip

For the vast majority of applications this setup will work fine. Should you wish to implement a different strategy, though, you can supply your own idFunction in your model options:

import { newInstance, ObjectData } from "@visuallyjs/browser-ui"

const modelOptions = {
  idFunction: (data:ObjectData):string {
    return SomeCustomComputing(data);
  }
})
}
const model = newInstance(modelOptions)

const surface = model.render({})

Remember to pass back the ID as a string. This method will be used to attempt to derive an ID for any model object.

Again note this is optional - you do not need to supply this function, but if you do not then VisuallyJs will expect an id member in your data.

Group IDs

IDs for groups are derived using whatever method VisuallyJs is using to derive IDs for nodes - either by looking for an id value in your data, or by using a supplied idFunction. group IDs must be unique across all groups and nodes in the dataset: you cannot have a group that has the same ID as some node.

Edge IDs

You are not required to supply an ID for every edge, and if you do not, VisuallyJs will assign one automatically.

Port IDs

Port IDs are required to be unique on the node/group on which the port exists, but may be the same as the ID of a port on some other node (and in fact this is quite common).

Referencing ports by ID

When adding an edge to a VisuallyJs instance, you can reference a port on some node using, by default, dotted notation. In the data given above there were three ports. We could connect one of them to a column on another table like this:

model.connect({
  source:"book.id", 
  target:"book_author.book_id"
})

book_author is another table in the schema from the SchemaBuilderDemoLink title="Schema Builder"/> starter app.

Custom port ID Separator

If you find that using a period as the separator in a port ID does not work for your data model, you can override what VisuallyJs will use by doing this:

import { newInstance } from "@visuallyjs/browser-ui"

const modelOptions = {
  portSeparator: "#"
}
const model = newInstance(modelOptions)

const surface = model.render({})

Object type

Every object has an associated type. This is an important concept in VisuallyJs, as it is the basic means by which the data model is bound to any renderers, via views.

The type of a model object is, by default, mapped by the object's type in its backing data. It is used by the view in the UI to determine the appearance and behaviour of the object.

To change the type of some object after it has been initially created, use the setType method on a model instance. For a discussion, see this page

tip

As with ID, you can provide your own function to retrieve the type for some object, should you need to.

import { newInstance, ObjectData } from "@visuallyjs/browser-ui"

const modelOptions = {
  typeFunction: (data:ObjectData):string => {
  return SomeOtherComputing(data);
}
}
const model = newInstance(modelOptions)

const surface = model.render({})

Constraining connectivity

Connectivity can be controlled at runtime by interceptors - callbacks that can be used to cancel some proposed activity, and that are bound on an instance of the VisuallyJs model by supplying a specific function in the model constructor options.

beforeConnect

A function to run before an edge with the given data can be established between the given source and target. Returning false from this method aborts the connection. Note that this method fires regardless of the source of the new edge, meaning it will be called when loading data programmatically.

Method signature

beforeConnect(source: Vertex, target: Vertex): any

Parameters

source The source vertex for the new edge
target The target vertex for the new edge

Return value

false - aborts the connection
all other values are ignored and will allow the edge to be established

Example

Here, we reject connections from any vertex to itself.

import { newInstance } from "@visuallyjs/browser-ui"

const modelOptions = {
  beforeConnect: (source: Vertex, target: Vertex) => {
      return (source !== target)
  }
}
const model = newInstance(modelOptions)

const surface = model.render({})

beforeMoveConnection

A function to run before an edge of the given type is relocated from its current source or target to a new source or target. Returning false from this method will abort the move.

Method signature

beforeMoveConnection(source: Vertex, target: Vertex, edge: Edge): any

Parameters

source Candidate source. May be the edge's current source, or may be a new source.
target Candidate target. May be the edge's current target, or may be a new target.
edge The edge that is being moved.

The parameters source and target reflect the source and target of the edge if the move were to be accepted. So if, for example, your user drags a connection by its target and drops it elsewhere, target will be the drop target, not the edge's current target, but source will be the edge's current source. You can access the current source/target via the source and target properties of edge.

Return value

false - aborts the move
all other values are ignored and will allow the move to occur

Example

Here, we reject moving any edge that has fixed:true in it backing data:

import { newInstance } from "@visuallyjs/browser-ui"

const modelOptions = {
  beforeMoveConnection: (source: Vertex, target: Vertex, edge:Edge) => {
      return (edge.data.fixed !== true)
  }
}
const model = newInstance(modelOptions)

const surface = model.render({})

beforeStartConnect

A function to run before an edge of the given type is dragged from the given source (ie. before the mouse starts moving). This interceptor is slightly different to the others in that it's not just a yes/no question: as with the other interceptors, returning false from this method will reject the action, that is in this case it will not allow a connection drag to begin. But you can also return an object from this method, and when you do that, the connection start is allowed, and the object you returned becomes the payload for the new edge.

Method signature

beforeStartConnect(source: Vertex, type: string): any

Parameters

source The vertex that is the source for the new edge
type The computed type for this new edge.

Return value

false - aborts the connection
Object - An object returned from this method will be used as the initial payload for the new edge
all other values are ignored and will allow the connection start to continue

Example - reject a connection start

import { newInstance } from "@visuallyjs/browser-ui"

const modelOptions = {
  beforeStartConnect: (source: Vertex, type:string) => {
      return type !== 'not-connectable'
  }
}
const model = newInstance(modelOptions)

const surface = model.render({})

Example - provide an initial payload

import { newInstance } from "@visuallyjs/browser-ui"

const modelOptions = {
  beforeStartConnect: (source: Vertex, type:string) => {
      return {
          type,
          message:`initial payload for vertex ${source.id}`
      }
  }
}
const model = newInstance(modelOptions)

const surface = model.render({})

beforeDetach

A function to run before the given edge is detached from the given source vertex. If this method returns false, the detach will be aborted.

Method signature

beforeDetach(source: Vertex, target: Vertex, edge: Edge, isDiscard?: boolean): any

Parameters

source The source vertex for the edge that is to be detached.
target The candidate target for the edge - may be null, if the edge is being discarded
edge The edge that is being detached.
isDiscard True if the edge is not now connected to a target.

Return value

false Returning false will abort the edge detach
all other values are ignored and will allow the detach to occur

Example

Here, we reject the detach if the target is null, ie. the user is trying to discard the edge, not relocate it.

import { newInstance } from "@visuallyjs/browser-ui"

const modelOptions = {
  beforeDetach: (source: Vertex, target: Vertex, edge: Edge, isDiscard?: boolean) => {
      return target != null
  }
}
const model = newInstance(modelOptions)

const surface = model.render({})

beforeStartDetach

Method signature

beforeStartDetach(source: Vertex, edge: Edge): any

A function to run before the given edge is detached from the given source vertex. If this method returns false, the detach will be aborted. The difference between this and beforeDetach is that this method is fired as soon as a user tries to detach an edge from an anchor in the UI, whereas beforeDetach allows a user to detach the edge in the UI.

Parameters

source The source vertex for the edge that the user has started to detach
edge The edge that the user has started to detach

Return value

false Returning false will abort the edge detach
all other values are ignored and will allow the user to begin the detach

Example

Here, we reject the detach if the source vertex has doNotDetachEdges:true in its backing data.

import { newInstance } from "@visuallyjs/browser-ui"

const modelOptions = {
  beforeDetach: (source: Vertex, edge: Edge) => {
      return source.data.doNotDetachEdges !== true
  }
}
const model = newInstance(modelOptions)

const surface = model.render({})

Multiple interceptors

You can provide multiple interceptors - in this example we provide a beforeStartConnect and beforeDetach interceptor to the model. The beforeStartConnect interceptor prevents the user from dragging connections from any vertex whose ID is not an even number. The beforeDetach interceptor reattaches detached connections whose source ID is not an event number

import { newInstance } from "@visuallyjs/browser-ui"

const modelOptions = {
  beforeStartConnect: (source, type) => {
      // only allow connections from nodes whose 
      // ID is an even number
      return parseInt(source.id, 10) % 2 === 0
  },
  beforeDetach: (source, target, edge, isDiscard) => {
      // only allow connections to be detached whose 
      // source ID is an even number
      return parseInt(edge.source.id, 10) % 2 === 0
  }
}
const model = newInstance(modelOptions)

const surface = model.render({})

Next Steps

Add, remove and update

Read about how to add, remove and update data

Undo/redo and transactions

Read about how to undo/redo operations, and work with transactions

Selections

Read about how to generate and work with selections

What do I need the model for?​

Accessing the model​

Data Format​

Object IDs​

Group IDs​

Edge IDs​

Port IDs​

Referencing ports by ID​

Custom port ID Separator​

Object type​

Constraining connectivity​

beforeConnect​

Method signature​

Parameters​

Return value​

Example​

beforeMoveConnection​

Method signature​

Parameters​

Return value​

Example​

beforeStartConnect​

Method signature​

Parameters​

Return value​

Example - reject a connection start​

Example - provide an initial payload​

beforeDetach​

Method signature​

Parameters​

Return value​

Example​

beforeStartDetach​

Method signature​

Parameters​

Return value​

Example​

Multiple interceptors​

Next Steps​

What do I need the model for?

Accessing the model

Data Format

Object IDs

Group IDs

Edge IDs

Port IDs

Referencing ports by ID

Custom port ID Separator

Object type

Constraining connectivity

beforeConnect

Method signature

Parameters

Return value

Example

beforeMoveConnection

Method signature

Parameters

Return value

Example

beforeStartConnect

Method signature

Parameters

Return value

Example - reject a connection start

Example - provide an initial payload

beforeDetach

Method signature

Parameters

Return value

Example

beforeStartDetach

Method signature

Parameters

Return value

Example

Multiple interceptors

Next Steps