Component Overlays and Quality Codes
Component overlays are driven by the Expert 
Data Quality Property. Feel free to bind this property or externally control it to manipulate overlays.
Most components support overlays to clearly indicate state conditions to the end user, which is based on the component's quality code. These represent such things as: stale data, insufficient permissions, incorrect configuration, write pending, etc.
Overlays are defined separately for each component. Each overlay often corresponds to many different quality codes.
Quality codes indicate states of reliability of data. Many codes match up to OPC specification.
A component's quality is determined by the quality of the worst bound property. This value is stored in the (Expert) Data Quality property. -1 means no overlay.
| Quality Code | State |
|---|---|
| 0 | Bad Data from OPC |
| 4 | CONFIG_ERROR |
| 8 | NOT_CONNECTED |
| 12 | DEVICE_FAILURE |
| 16 | SENSOR_FAILURE |
| 20 | Bad, showing last value |
| 24 | COMM_FAIL |
| 28 | OUT_OF_SERVICE, SERVER_DOWN |
| 32 | WAITING |
| 64 | UNCERTAIN |
| 68 | UNCERTAIN, showing last |
| 80 | SENSOR_BAD |
| 84 | LIMIT_EXCEEDED |
| 88 | SUB_NORMAL |
| 192 | Good Data |
| 216 | Good, with local override |
| 256 | OPC_UNKNOWN |
| 300 | Config Error |
| 301 | Comm Error |
| 310 | Expr Eval Error |
| 330 | Tag exec error (FSQL) |
| 340 | Type Conversion Error |
| 403 | Access Denied |
| 404 | Not Found |
| 410 | Disabled |
| 500 | Stale |
| 600 | Unknown (loading) |
| 700 | Write Pending |