Node Design Guidelines

Nodes

There are three types of node.

• an Input node sits at the start of a flow. It is typically triggered by some external event occurring.
• a Function node sits in the middle of a flow. It performs actions based on the incoming messages and passes on the resulting messages. One sub-type of Function node is a Query node that is used to retrieve data from an external API, such as a database query or a web services call.
• an Output node sits at the end of a flow. It consumes the incoming messages and triggers an action.

Conventions

(under development)

• Message property conventions

• data in the node settings overwrites that in an incoming message
• If data in the incoming message is not valid, the node should......? (Question: in this case should the node issue a warning? or an error? and/or change its status? or ignore this silently?)

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Work in progress:

• Input node feature definitions
• Query node feature definitions
• Watch node feature definitions
• Output node feature definitions