Geometric networks in a geodatabase in Informix

Geometric networks are collections of line (edge) and point (junction) feature classes in a feature dataset that possess a connectivity relationship. Geometric networks are legacy dataset types used to model utility infrastructure, such as electric lines and sewer systems.

The tables that are created with a network depend on whether there are turns present in the network.

Geometric networks in a geodatabase in IBM Informix

Geometric networks are tracked in the gdb_items table. The gdb_itemtypes table stores a value indicating that the object is a geometric network. The gdb_itemrelationships table stores information on how the network and the feature dataset it is in are related.

In addition to these tables, networks are made up of a set of variably sized tables that is stored in the schema of the user who created the geometric network. The size of these tables depends on the size of the network—for example, the number of junctions and number of edges can affect the network size.

There are 9 fixed tables per network, and they are identified by the following naming convention: N_<ID>_<table_descriptor>, where ID represents a logical network ID, which is stored in the networks definition in the gdb_items table; for example, N_1_<table descriptor>, N_2_<table descriptor>.

The actual number of tables varies depending on what elements the network contains. A maximum of 21 tables could be created for a network with turns and weights.

All these tables are versioned when the network itself is versioned.

The following tables are always created: n_<id>_desc, n_<id>_e<#>, n_<id>_estatus, n_<id>_etopo, n_<id>_flodir, n_<id>_jdesc, n_<id>_jstatus, n_<id>_jtopo, and n_<id>_props.

Note:

The N_<ID>_* tables can be viewed in the DBMS but should not be altered using SQL/third-party applications; doing so can corrupt the network.

n_<id>_*

Tables in the geodatabase that begin with N_ store information about networks.

n_<id>_desc

The n_<id>_desc table describes the elements of a network. This is a normalized table whose row count is equal to the number of junctions and the number of edges in a geometric network.


Field name	Field type	Description	Null?
oid	integer	The unique identifier of an element in a geometric network	NOT NULL
userclassid	integer	The identifier of the feature class to which the element belongs	NOT NULL
userid	integer	The ObjectID of the feature	NOT NULL
usersubid	integer	The identifier of an element in a feature; only applicable to complex edge features	NOT NULL
elementtype	smallint	A code indicating the type of network element; either 1 = junction or 2 = edge	NOT NULL
eid	integer	The unique element identifier of the network element; only unique for the type of network element	NOT NULL

n_<id>_props

The n_<id>_props table contains a summary description of a network's properties, such as element counts and maximum EID values.


Field name	Field type	Description	Null?
propertyid	integer	The unique identifier of the network property	NOT NULL
propertyname	varchar(32)	The name of the property	NOT NULL
propertyvalue	integer	The value of the property	NOT NULL

All the remaining network tables contain the same field names and types. The table names and what they track are described below the table definition.


Field name	Field type	Description	Null?
oid	integer	The unique identifier of the BLOB page in the table	NOT NULL
pagenumber	integer	The number of the BLOB page in the table	NOT NULL
pageblob	BLOB	The actual BLOB page, which contains a description for the element the table is describing, such as edge and edge status

n_<id>_e<#>—Describes network edge weights; # = 2, 3, 4, or 5
n_<id>_edesc—Describes the edges in a network
n_<id>_estatus—Describes the status of each edge including its deleted and disabled states
n_<id>_etopo—Describes the network edge topology or connectivity
n_<id>_flodir—Describes the network flow direction
n_<id>_j<#>—Describes network junction weights; # = 0 or 1
n_<id>_jdesc—Describes the network junctions
n_<id>_jstatus—Describes the status of each network junction including its deleted and disabled states
n_<id>_jtopo—Describes the connectivity of junction elements with edge elements
n_<id>_jtopo2—Describes the connectivity of junction elements with edge elements when there are multiple edges connected to a single junction
n_<id>_t<#>*—Describes the weight values of each turn element
n_<id>_tdefn*—Defines each turn element by listing the edges and junctions that make up the turn
n_<id>_tdefn2*—Overflow table for the turn element definition; for example, if multiple edges make up a turn
n_<id>_tdesc*—Describes the turns in a network
n_<id>_tstatus*—Describes the status of each network turn, including its deleted and disabled states

View a diagram of a geometric network in Informix.

Dashed lines indicate implicit relationships between columns.

Note:

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For a description of the build errors table, see Network build errors table schema.