Operating Node Reduction By Priority rules

Prerequisite:

Before configuring a Node Reduction By Priority rule, you must check that the node schematic feature class required for the rule execution already exists in the schematic dataset and is associated with the schematic diagram template on which the rule is going to be specified.

Before learning more about the Node Reduction By Priority rule configuration, there are also some terms specific to this rule you have to know:

• The reduced nodes are nodes that will be not graphically contained anymore in the final resulting diagram.
• The target nodes are nodes that connected the reduced nodes before their reduction and that are used to reconnect the links that connected to those reduced nodes so the network topology is preserved after reduction.
• For a reduced node with N connections, (N - 1) links are created to connect the target node. These links are super spans. The link that connected the reduced node to the target node is the reduced link in the generated diagram. This link doesn't physically display in the diagram, but its related properties are reported on each of the (N - 1) super span links.

Node Reduction By Priority rules allow you to generate schematic diagrams after all nodes or some particular nodes implemented by a given node schematic feature class have been removed and after the links that connected these removed nodes have been reconnected to a target node so the topology is preserved.

The reduced nodes are nodes implemented by a given node schematic feature class that will not be contained in the final resulting diagram. You can choose to reduce all the nodes implemented by that specified node schematic feature class or only some of them that have been filtered out according to the following:

• A SQL filter that works on the real feature class/object table associated with that node schematic feature class
• Constraints based on their number of connections (that is, constraints based on the numbers of links that connect these nodes)
• An extended criteria that has been specifically developed to determine which nodes are going to be reduced
• Any particular schematic attribute expected on the schematic links incident to the nodes to be reduced, or any field expected on the real feature classes associated with the link schematic feature classes that implement the links that connect the node candidate to the reduction

For example, the rule can reduce the following:

• Nodes with two connections for the specified schematic feature class
• Only nodes implemented by this schematic feature class, which match particular field values
• Only nodes to which connected links match a particular property value detected by an extended criteria
• Only nodes for which all the connected links have the same specific attribute for their associated real features and for which that attribute has the same values for all those associated features
• Nodes that verify these four types of criteria at the same time

The steps below focus on the configuration of the Node Reduction By Priority Rule Properties page that displays when clicking the Rule Properties button on the Rules tab toolbar while such a Node Reduction By Priority rule has already been added to that tab. To learn about how to add any new rule item on the Rules tab and display the Rule Properties page, read the Specifying a schematic rule on a schematic diagram template topic.

For a Node Reduction By Priority rule that has just been added on the Rules tab, clicking the Rule Properties button on the Rules tab toolbar opens the Rule Properties dialog box as follows:

Steps:

1. Type a description for the rule in the Description field.

   This description string will display on the Rules tab for the related rule item and will also display during schematic diagram generations and updates to inform users that the rule is being executed.

2. Select the name of the node schematic feature class to be reduced from the Select the node schematic feature class to reduce drop-down list.

   All node schematic feature classes that are associated with the schematic diagram template are available from this drop-down list.

   At this step of the rule configuration, all the schematic nodes based on that selected node schematic feature class are configured to be reduced.

3. Check the Keep vertices check box if you want the vertices displayed along the links that connect to the reduced node to be kept after nodes are reduced.

   When this box is checked, a vertex is also displayed at the reduced node location.

   Note:

   This option is interesting for diagrams that aren't laid out, that schematic features display at their geographic coordinates, and for which the schematic links display with initial vertices. For diagrams that are laid out and updated after a route node reduction rule has been configured, no vertex is added at the reduced node location to preserve the saved layout.

4. If you want to specify a SQL filter on the specified node schematic feature class so only certain ones are reduced, do the following:
   1. Click the Edit button at the right of the SQL Filter on associated feature/object class area.

      The SQL Query dialog box opens.

   2. Build the SQL expression you want.

      The filtering operates on the fields stored on the feature class or object class that is associated with the specified node schematic feature class.

   3. Click OK.

      The SQL Query dialog box closes, and the SQL filter you have just specified automatically displays in the SQL Filter on associated feature/object class area.

   The specified SQL filter will then be used to determine the subset of schematic nodes reduction candidate. Those that don't verify the SQL filter will not be reduced during the rule execution.

5. On the Node connection constraints for reduction section, specify whether all or only some of the schematic nodes reduction candidates will be reduced, depending on the number of their connected links:
   • Choose No connection constraint if you want all the schematic nodes reduction candidates to be reduced.
   • Choose Connection constraint if you want schematic nodes reduction candidates to be reduced according to their number of connections—that is, according to the number of links that connect this node:
     • Check the Reduce nodes with 0 connections box if you want to reduce all nodes with no connected links.
     • Check the Reduce nodes with 1 connection box if you want to reduce all nodes with only one connected link.
     • Check the Reduce nodes with 2 connections box if you want to reduce all nodes with only two connected links.
     • Check the Reduce nodes with > 2 connections box if you want to reduce all nodes with at least three connected links.
     Note:

     Several boxes can be checked. For example, checking both the Reduce nodes with 0 connections and Reduce nodes with 2 connections boxes allow you to reduce nodes that are disconnected and nodes with two connected links in the same rule execution.

6. To determine the nodes to reduce, you can also specify a constraint based on a schematic attribute configured on the schematic links incident to the nodes to be reduced or on a field stored on the real features/objects associated with the schematic links incident to the nodes to be reduced. This constraint must be specified on the Connected link attribute section:
   1. Check the Use attribute name check box.
   2. Type the name of the schematic attribute or field that will be used.

      For each schematic link that connects to a node reduction candidate, the rule first searches for a schematic attribute with this name on the schematic link. If no schematic attribute with this name is detected, the rule searches for a field with the same name on the GIS feature associated with the schematic link. The node will then be reduced only if the detected attributes or fields exist with the same value for all its connected links.

7. A specific extended criteria can also be specified to filter out the nodes reduction candidate. To use such a criteria, you must configure the parameters on the Extended criteria section:
   1. Check the Use extended criteria check box.
   2. Select the desired extended criteria from the drop-down list.

   An extended criteria for the Node Reduction By Priority rule is a component that implements the esriSchematic.ISchematicNodeReductionExtended interface.

   Note:

   The Use extended criteria drop-down list and the Use extended criteria check box on the Node Reduction By Priority rule attributes dialog box are unavailable when no custom extended reduction criteria have been registered on the computer.

   The extended criteria component works on the nodes reduction candidate according to all the other specified reduction options. It determines whether each node will be finally reduced after the rule execution. It can also determine the target node used to reconnect all the links connected to the reduced node.

8. Define how the topology of the network will be preserved once the specified nodes are reduced—that is, specify the target nodes that will be used to reconnect the links connected to the reduced nodes.
   • Choose Select the nearest node if you want the nearest node connecting to the reduced node to become the target node. In this case, the target detection only depends on the distance between the reduced node and its connected nodes. The nearest node becomes the target node, and the process is independent of the schematic feature class on which this target node is based.
     Caution:

     The distances between nodes are computed according to their geographic locations. If you update a diagram after having specified a new node reduction by priority rule, don't forget that the node locations you see in the diagram before updating it are perhaps not the geographic locations. In this case, if the nodes contained in your schematic diagram are not displayed at their geographic coordinates, the detected target may not appear as the nearest node.

   • Choose Select the highest priority node if you want the target node that will connect the links that were connected to the reduced nodes to be detected according to priorities set for the node schematic feature classes.

     In this case, for each node connected to the reduced node, the reduction rule analyzes the options specified in the Target node priority options section before detecting the right target node.

     • If among all the nodes that connect the reduced node, only one node belongs to the schematic feature class with the highest priority, this node becomes the target node.
     • If among all the nodes that connect the reduced node, no node belongs to the schematic feature class with the highest priority, the rule will check whether there is a connected node belonging to the schematic feature class defined with the second-level priority, and so on.
     • If among all the nodes that connect the reduced node, several nodes belong to the schematic feature class with the highest priority, the rule will detect the target node according to the options specified in the Multiple choices solving subsection.

   The parameters in the Target node priority options section are advanced parameters.

   • The Schematic feature class list ordered by decreasing priorities area contains all the schematic feature classes associated with the diagram template listed in their priority order—that is, from the schematic feature class having the highest priority to the schematic feature class having the lowest priority. To change a schematic feature class priority level, click and drag the schematic feature class entry to another level in the list and drop it.
     Note:

     When a link schematic feature class is prior, the rule considers the links connecting the reduced node instead of the nodes connected to the reduced node. The target node is the origin or the extremity node of the link implemented by that link schematic feature class that connects to the reduced node.

   • The Multiple choices solving subsection allows you to specify how the rule will choose the target node when there is conflict with several candidate target nodes—that is, when several nodes belong to the schematic feature class with the highest priority.

     Checking the Select the nearest node if conflict between two nodes with same priority check box causes the nearest node to the reduced node to become this target node if the schematic feature class related to these nodes in conflict is checked in the Check schematic feature classes for which the nearest node is selected when conflict between more than two nodes section.

     Note:

     If the schematic feature class that implements the nodes in conflict is not checked in the Check schematic feature classes for which the nearest node is selected when conflict between more than two nodes section, the node to reduce will not be reduced.

     For example, if two nodes of the X schematic feature class with the highest priority connect the same node to reduce, these X nodes are both candidates to be the target node. In this case, if the Select the nearest node if conflict between two nodes with same priority check box is checked, and if the X-related schematic feature class check box is also checked in the Check schematic feature classes for which the nearest node is selected when conflict between more than two nodes list, the nearest X node to the reduced node will be the target node. If the Select the nearest node if conflict between two nodes with same priority option is checked, but the X-related schematic feature class check box is not checked in the Check schematic feature classes for which the nearest node is selected when conflict between more than two nodes list, the reduction by priority rule will not try to resolve the conflict for the X nodes candidate to become the target node, and the node to reduce will not be reduced.

9. Click OK to close the Rule Properties dialog box.

Node Reduction rule sample results