A network topology contains a set of edges or links. Each link has a node at each end. Multiple links can intersect at a single node.
A polygon topology represents an area coverage.
Topologies describe relationships between drawing objects. There are three types of topology:
- Node, also called point
- Network
- Polygon
A node topology contains a set of points.
A network topology contains a set of edges or links. Each link has a node at each end. Multiple links can intersect at a single node.
A polygon topology represents an area coverage. The borders of polygons are represented by edges. The polygons in a polygon topology cannot overlap, but adjacent polygons share edges.
Each object in the topology (node, link, or polygon centroid) has an ID number that is unique within the topology.
Internally, the relationship between drawing objects and topologies is implemented using object data tables. For a topology named topol_name, the following tables are used:
- TMPCNTR_topol_name
- TPMDESC_topol_name
- TPMID_topol_name
- TPMLINK_topol_name
- TPMNODE_topol_name
TPMDESC and TPMID are not attached to any drawing objects. They are used to store information about the topology itself. TPMDESC contains the parameters used to create the topology, such as topology type, colors, and layer names. TPMID contains a single value for the last id assigned for the topology.
TPMNODE data is attached to nodes in the topology. Each node has an ID and a resistance value.
TPMLINK data is attached to links between nodes. For network topologies the link has values for the ID, start and end node, direction of the link, and resistance values for traversing the link in each direction. For polygon topologies the link also has values for the polygons on either side of the link.
TPMCNTR data is attached to the centroids of polygons in a polygon topology. Each centroid has values for the ID, area, perimeter, and number of links that form the edges of the polygon.
In most cases, applications do not need to manage the object data directly. The topology API calls perform all the necessary updates. An application needing to know which topologies have been defined in the drawing, however, should check the object data tables for names beginning with “TMPDESC_”.