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DAIS is flexible in terms of what types and properties may exist in a server.
In OPC there is a recommendation of what properties are expected to be supported by a data access server. These recommended
properties are shown in
Table 4-1. The column
names correspond to the attributes in the Property class seen in Figure 4-4.
Table 4-1 Recommended Properties
label |
id |
canonical_data_ type |
description |
||
| engineeringUnit | 100 | STRING_TYPE | Engineering unit. | ||
| description | 101 | STRING_TYPE | Description. | ||
| maxValue | 102 | DOUBLE_TYPE | Maximum value. | ||
| minValue | 103 | DOUBLE_TYPE | Minimum value. | ||
| sensorMaximum | 104 | DOUBLE_TYPE | Maximum value from an analog input sensor. | ||
| sensorMinimum | 105 | DOUBLE_TYPE | Minimum value from an analog input sensor. | ||
| closedLabel | 106 | STRING_TYPE | Text for the closed state for a discrete status input. | ||
| openLabel | 107 | STRING_TYPE | Text for the open state for a discrete status input. | ||
| itemTimeZone | 108 | UNSIGNED_TYPE | |||
| 109-4999 | Reserved by OPC. |
For a system having data described by a particular schema (for example, the CIM for power systems) the implementation of that
schema as seen through DAIS has to be decided. Either a mapping to the recommended OPC properties can be made or the schema
can be exposed as is through DAIS. This is however outside the scope of this specification.