For all Variables specified in this specification, the Attributes named in Table 5 shall be set as specified in the table. The definitions for the Attributes can be found in OPC 10000-3.
Table 5 – Common Variable Attributes
|
Attribute |
Value |
|
MinimumSamplingInterval |
Optionally, a vendor-specific minimum sampling interval is provided. |
|
AccessLevel |
The access level for Variables used for type definitions is vendor-specific, for all other Variables defined in this specification, the access level shall allow reading; other settings are vendor-specific. |
|
UserAccessLevel |
The value for the UserAccessLevel Attribute is vendor-specific. It is assumed that all Variables can be accessed by at least one user. |
|
Value |
For Variables used as InstanceDeclarations, the value is vendor-specific; otherwise it shall represent the value described in the text. |
|
ArrayDimensions |
If the ValueRank does not identify an array of a specific dimension (i.e. ValueRank <= 0) the ArrayDimensions can either be set to null or the Attribute is missing. This behaviour is vendor-specific. If the ValueRank specifies an array of a specific dimension (i.e. ValueRank > 0) then the ArrayDimensions Attribute shall be specified in the table defining the Variable. |
|
Historizing |
The value for the Historizing Attribute is vendor-specific. |
|
AccessLevelEx |
If the AccessLevelEx Attribute is provided, it shall have the bits 8, 9, and 10 set to 0, meaning that read and write operations on an individual Variable are atomic, and arrays can be partly written. |