Sometimes things don't go quite as expected. Connections get broken, switches die, machines crash. Aside from taking reasonable steps to prevent these occurrences, it is especially important in HMIs to be able to gauge the health and accuracy of what is displayed at a glance. In a highly distributed system like Ignition, it is especially important, as the client may be located at quite a distance (maybe across the world) from the physical process it is monitoring and controlling.
For these reasons, components will get visual overlays for various reasons to indicate that the data they are displaying is not good. Each data binding that drives a component is evaluated for quality. If any of these qualities becomes poor, the component will show an overlay. The different overlays can mean different things, denoting their underlying cause. These follow the Quality properties of SQLTags.
