Quoted from OpenNMS website
OpenNMS is an open source, world’s first enterprise grade network management platform. It consists of a community supported open-source project as well as a commercial services, training and support organization.
As a network management platform, it provides several major feature categories:
1. Discovery – finding out what equipment is on your network, and adding it to the database
2. Monitoring – keeping track of the status of networked equipment
3. Events – receiving, correlation and sending notifications
4. Data collection – collection, storage, and reporting of various network available data points.
Surveillance View Dashlet
The surveillance view dashlet mimics the visual representation of node status shown in the Surveillance View feature. However, it also is a special Dashlet in the fact that it controls the content of all other Dashlets on the page. When it is first displayed, it sets the a filtering criteria on all the other Dashlets that restricts the data they present to the set of nodes that can be found in the view. In the “drv4doe” example above, the view is restricted to only show the nodes that fit in the subset of nodes represented by the intersection of the Production category with the Servers category. When multiple rows and/or columns are shown, as in the default view, the other Dashlets can be further restricted by the clicking on one of the row or column headers or on one of the table cells itself. The example below shows how the selection is highlighted in blue