When a process is created, a list of items can be given as an input parameter. The items are a list of nodeids. A nodeId is a nodeRef with the workspace://SpacesStore prefix removed. During creation of the process, a new package node is created in the repository. All provided items are associated with that package node.
The package nodeid is stored as a variable in the process with variable name 'package' as a String. When retrieving the process details, the list of 'items' is generated by collecting all the items that are associated with the package node.