Since a the set of activities and transitions in a process form a Graph, Graph Theory can be applied to catch several well-known structural problems before a process is ever executed.
For example: consider a process in which an activity has a transition to another activity, which in turn has a transition back to the first activity. This forms a cycle in the process graph.
If there were no conditions on the transitions, the process would be guaranteed to end up in an infinite loop. These loops are known as informal loops (or 'ad-hoc' loops) and their presence renders several useful structural validations impossible. For this reason (among others), Cúram workflow provides formal constructs for delimiting iterative sections of a process (the loop-begin and loop-end activities). This allows it to detect the presence of ad-hoc loops in processes and prevents such processes from being released.
GOTO is analogous to ad-hoc loops in a workflow. The curly braces are analogous to the formal loop-begin and loop-end activities in a workflow.