What is a Node? What is a Workflow?

In KNIME Analytics Platform, individual tasks are represented by nodes. They are the smallest possible unit in KNIME and have been created to perform all sorts of tasks, including reading/writing files, transforming data, training models, creating visualizations, and so on. A sequence of nodes creates a workflow.

A workflow - as a sequence of nodes - is the graphic equivalent to a script or a series of instructions. Nodes can be connected via their input and output ports to form a workflow. Only similar types of input and output ports can be connected.

For example, the data output of this node, denoted by this black triangle, can only be connected to another black triangle i. e. the data input of another node.

Also notice that we can’t execute the node’s task if there’s no connection going to one or more of the required inputs! Each node has a status. The traffic light shows the node’s status.

Red is when you add a new node to your workflow editor, its status is not configured. Yellow - when you are configuring a node, the traffic light changes from red to yellow, that means, from not configured to configured. This means it is now ready to run its task but it hasn’t done that yet.

Green - the green light indicates that the node has run its task successfully and you can inspect the output. A red cross means that that the node has run the task but execution was unsuccessful.