Although, in the kernel of the TIGER language, a node must not be dominated by more than one node, we have added so-called secondary edges as an extra layer in order to allow for structure sharing in syntax graphs. A secondary edge defines an additional parent node for a given node.
| >~L | labelled secondary edge |
| >~ | secondary edge |
| !>~L | negated labelled secondary edge |
| !>~ | negated secondary edge |