The parcels.shp sample data will be used to demonstrate how to set up and test topological relationships. Here, the parcels polygon shapefile is loaded and the Topology Checker panel has been enabled by clicking on the Topology Checker button 
or Topology Checker under the Vector menu. The following screenshot shows the parcels.shp sample data loaded into QGIS desktop and the Topology Checker plugin enabled:
Here are the steps for configuring the Topology Checker plugin and evaluating the topology of the parcels.shp ...
