The Set Starting Point rule is used to preset network elements represented in the diagram as starting points.
The Set Starting Point rule can be configured to preset network features or objects currently represented in the diagram as starting points. When those features or objects are junctions with terminals, the rule can be used to preset starting points on the specific terminals as well.
When a Set Starting Point rule is preset before a Trace rule, it identifies the specified starting points as the only starting points instead of running all the network elements represented in the diagram at the time it executes.
Set Starting Point rule process
When the Set Starting Point rule is configured without an SQL expression or junction terminal, all the network elements of the specified network source class or object table can be considered as starting points for Trace rule execution.
When both an SQL expression and junction terminals are configured, only the network elements queried from the specified network source class or object table that have the specified terminals can be considered as starting points for Trace rule execution.
Since any content feature always exists in a diagram with its container by default, you may have to specify the content or container feature as the starting point to prevent the trace from failing.
In the rule sequence configured for a diagram template, several Set Starting Point rules can be specified before a Trace rule. Each rule searches for the starting points it expects among the network elements currently represented in the diagram and merges those that are detected in an internal list. When the Trace rule starts, the process considers the starting points in this internal list and executes the trace from only these starting points. If the starting points list is empty, in other words, if none of the elements in the diagram match the Set Starting Point rules criteria, the Trace rule is skipped.
Trace rules can also be chained to build diagram contents. In this situation, any starting points set by the Set Starting Point rules positioned before the first Trace rule in the rule sequence are considered by that Trace rule when it starts. These starting points are kept for the execution of the second Trace rule in the rule sequence, unless there are other Set Starting Point rules positioned between the first and second Trace rules. In this case, this second set of Set Starting Point rules is considered to build a new internal starting points list to use as input for the second trace. The principle is the same if there is a third Trace rule configured in the rule sequence, and so on.
When the Trace rule is configured to execute the Shortest Path trace type, precisely two starting points—no more, no less—are expected.
Set Starting Point rule configuration
To configure a Set Starting Point rule on a template, use the Add Set Starting Point By Attribute Rule tool.