The concept of nodes is used to describe the individual interaction points within the experience.
They are the puzzle pieces that join together to form the overall experience.
Nodes allow you to work through & consider the details of interaction points without having to place them in the bigger picture - without having to figure out where they fit - this comes later in Trajectory
Nodes can be generic, can be built from the same base (ie. an SMS interaction), it is the content, response and outcomes that will differ as the participant encounters them.
At a base level, nodes are concerned with the where, with what & how of the interactions within your experience. Defining what participants see, do, and what responses they get.
Work with nodes early on to help you record ideas for interactions - while out on a site visit, while talking to potential particpants. You might see or discover something that could form the basis of an interaction - using nodes will allow you to record this without having to know where it fits in.
In the early stages, certain aspects of the nodes (relationships for one) can be glossed over until you have a clearer idea of the overall experience. As your design develops, these nodes will become more and more detailed.
Once you are at a stage to start thinking about how they fit together, you can move onto trajectory & start putting the puzzle pieces together.
As you'll see in the diagram (mouse over to view example) to the right, nodes are described through the following:
External Influences are considered separately, as they don't make up the interaction but may have an impact on the node. This could be practical considerations such as approval, weather-proofing, security, local laws etc.