Parameters
- fromdata
- a node key identifying the node data from which the link comes
- fromparam
- an optional value identifying which port on the "from" node the link is connected to
- todata
- a node key identify the node data to which the link goes
- toparam
- an optional value identifying which port on the "to" node the link is connected to
- ignoreexistinglink
- true if relinking; false if adding a new link
- oldlinkdata
- the original link data that might be modified, if ignoreexistinglink is true
Return Value
The behavior of this predicate depends on the value of ValidCycle and ValidUnconnectedLinks.