Network attributes

Network attributes are associated with attributes on features in the 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 is an apportionable network attribute that you can use 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

User-defined network attributes are created using the Add Network Attribute tool and assigned to a feature class attribute field using the Set Network Attribute tool.

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
    • Nullable—Supports null values
  • Long—Large integer
    • Nullable—Supports null values
  • Double—Double precision
    • Apportionable
    • Nullable—Supports null values
  • Date
    • Nullable—Supports null values

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.

Apportionable network attributes

Defining a network attribute as apportionable specifies whether the network attribute will be apportioned across multiple edge elements belonging to the same network feature. The distribution of the value depends on the percentage along each edge element with respect to the from point of the original network feature.

Apportionable network attributes are configured with the apportionable property set to True. You can assign network attributes with the apportionable property to fields in line or point feature classes but only line features will display apportioned behavior. You can only set this property to True when the Attribute Type property is Double.

For apportionable network attributes, analytic results are more precise because apportionable values such as line length and other flow characteristics are computed for more accurate locations along a line. This means that trace analytics using apportionable network attributes with a function (Add, Average, Count, Max, Min, and Subtract) will return apportionable results based on edge elements of the network features. For example, using a function within a connected trace to count the shape length attribute returns a count based on the individual edge features and not the entire line. The aggregated geometry result type can also be used in a trace to return partial feature results when a function barrier using an apportionable network attribute evaluates to true midspan along a line feature.