DataSetDemo is an OrgChart sample, and as such nodes only have one parent (i.e. the boss).
Because of this, the data can be modeled as a single row, where the employee row that creates the node simple points to another employee row (via an employee ID) to be the boss.
If you want a more complicated graph (like a workflow) you need to model it with one table of node data and one table of link data (where each link row has a From Node and To Node pair).
DataSetDemo is actually coded to allow this if you create the tables correctly and change the calls to load the nodes and links. Read through the comments in the code.