Overview

Orange Canvas application is build around the a workflow model (scheme), which is implemented in the scheme package. Briefly speaking a workflow is a simple graph structure (most commonly a Directed Acyclic Graph - DAG). The nodes in this graph represent some action/task to be computed. A node (also commonly referred to as a widget) has a set of inputs and outputs on which it receives and sends objects.

The set of available node types for a workflow are kept in a (WidgetRegistry). WidgetDiscovery can be used (but not required) to populate the registry.

Workflow Model

The workflow model is implemented by Scheme. It is composed by a set of node (SchemeNode) instances and links (SchemeLink) between them. Every node has a corresponding WidgetDescription defining its inputs and outputs (restricting the node’s connectivity).

In addition, it can also contain workflow annotations. These are only used when displaying the workflow in a GUI.

Widget Description

• WidgetDescription
• CategoryDescription

Workflow Execution

• SignalManager

Workflow View

• The workflow view (CanvasScene)
• The workflow editor (SchemeEditWidget)