A geometric network is a set of connected edges (lines) and junctions (points), along with connectivity rules, that are used to represent and model the behavior of a common network infrastructure in the real world. Geodatabase feature classes are used as the data sources to define the geometric network. Rules for how resources flow through the geometric network and how to define the roles that various features will play in the geometric network are determined when creating feature class.
A geometric network is built within a feature dataset in the geodatabase. The feature classes in the feature dataset are used as the data sources for network junctions and edges. The network connectivity is based on the geometric coincidence of the features in the feature classes used as data sources. Each geometric network has a logical network—a collection of tables in the geodatabase that stores connectivity relationships and other information about the features in the geometric network as individual elements for use in tracing and flow operations.
Geometric networks are comprised of two types of features: edges and junctions. Edges and junctions in a geometric network are special types of features in the geodatabase called network features. Think of them as point and line features with extra behavior that is specific to a geometric network. Like other features in the geodatabase, they have behavior such as domains and default values. Since they are part of a geometric network, they have extra behavior such as an awareness that they are topologically connected to each other and how they are connected: edges must connect to other edges at junctions; in the network, the flow from one edge to another is transferred through junctions.