Network attributes are associated with attributes on features in your network. They are derived from feature attributes and cached inside the network topology to aid in performance while feature attributes are evaluated during a trace. The values stored as attributes for features on a map are reflected or updated in the associated network attribute each time you validate the network topology.
Existing network attributes can be viewed on the Trace Network Properties dialog box for the trace network. The Network Attributes tab includes detailed properties of existing network attributes and their assignments (the feature class and field to which the network attribute is assigned). This includes the system-provided and user-defined network attributes for a trace network that are available for tracing tasks.
The following system-provided network attributes in a trace network are listed on the Network Attributes tab:
- Source ID—The unique identifier for the network source in the trace network.
- Position from—Used to determine position along an edge for midspan connectivity.
- Position to—Used to determine position along an edge for midspan connectivity.
- Flow direction—Associated with all edge feature classes that participate in the network. This is created and assigned to the Flow direction field when a version 2 or later trace network is created, converted from a geometric network, or upgraded. This is used to determine the direction of flow for resources in the network.
- Shape length—Associated with the Shape_Length field on line feature classes in the network. This can be used to calculate the total length of a trace, for example, among a collection of streams or on a specific stream segment.
Create and assign network attributes
When creating a network attribute using the Add Network Attribute tool, the data type you choose for the Attribute Type parameter determines which options are available to define the network attribute. This also determines which attribute fields the network attribute can be assigned to using the Set Network Attribute tool after it is created, as the data types must match.
Network attributes can be created using one of the following attribute types:
- Short—Small integer
- Long—Large integer
- Double—Double precision
Keep the following in mind when configuring network attributes:
- To assign a network attribute to an attribute field using the Set Network Attribute tool, it must have a compatible data type, as listed above. If an attribute field with the correct data type is not present to set the network attribute, one can be added using the Add Field tool.
- Network attributes that are defined as not nullable can only be assigned to fields that share the same constraint for null values.
- There is no limit to the number of network attributes a single trace network can have; however, a network attribute can be associated with only one attribute per feature class. This means that once a network attribute is set on a network class for a specified field, no other network attribute assignments can be set on that field.
Work with network attributes
Tracing and network diagrams rely on network attribute information stored in a network topology. If changes are made to an attribute on a feature that is associated with a network attribute, a dirty area is generated to mark the feature for validation. Validating the network topology helps ensure information in the network topology is consistent for analytic events.
Network attributes are used to control traversability of features and act as weights to model the cost of tracing paths in the network. For example, in a water network, a certain amount of pressure is lost when traveling the length of a pipe due to surface friction in the pipes.