Hierarchy
Index
Properties
Optional accessLevel
Optional arrayDimensions
This Attribute specifies the length of each dimension for an array value. T The Attribute is intended to describe the capability of the Variable, not the current size. The number of elements shall be equal to the value of the ValueRank Attribute. Shall be null if ValueRank ? 0. A value of 0 for an individual dimension indicates that the dimension has a variable length. For example, if a Variable is defined by the following C array: Int32 myArray[346]; then this Variables DataType would point to an Int32, the Variable�s ValueRank has the value 1 and the ArrayDimensions is an array with one entry having the value 346. Note that the maximum length of an array transferred on the wire is 2147483647 (max Int32) and a multi-dimensional array is encoded as a one dimensional array.
Optional dataType
Optional dataValue
Optional historizing
The Historizing Attribute indicates whether the Server is actively collecting data for the history of the Variable. This differs from the AccessLevel Attribute which identifies if the Variable has any historical data. A value of TRUE indicates that the Server is actively collecting data. A value of FALSE indicates the Server is not actively collecting data. Default value is FALSE.
Optional minimumSamplingInterval
The minimumSamplingInterval Attribute indicates how 'current' the Value of the Variable will be kept. It specifies (in milliseconds) how fast the Server can reasonably sample the value for changes (see Part 4 for a detailed description of sampling interval). A minimumSamplingInterval of 0 indicates that the Server is to monitor the item continuously. A minimumSamplingInterval of -1 means indeterminate.
Optional userAccessLevel
The UserAccessLevel Attribute is used to indicate how the Value of a Variable can be accessed (read/write) and if it contains current or historic data taking user access rights into account. https://reference.opcfoundation.org/v104/Core/docs/Part3/8.57/
Optional valueRank
This Attribute indicates whether the Value Attribute of the Variable is an array and how many dimensions the array has. It may have the following values: n > 1: the Value is an array with the specified number of dimensions. OneDimension (1): The value is an array with one dimension. OneOrMoreDimensions (0): The value is an array with one or more dimensions. Scalar (?1): The value is not an array. Any (?2): The value can be a scalar or an array with any number of dimensions. ScalarOrOneDimension (?3): The value can be a scalar or a one dimensional array. NOTE All DataTypes are considered to be scalar, even if they have array-like semantics like ByteString and String.
The AccessLevel Attribute is used to indicate how the Value of a Variable can be accessed (read/write) and if it contains current and/or historic data. The AccessLevel does not take any user access rights into account, i.e. although the Variable is writable this may be restricted to a certain user / user group.
https://reference.opcfoundation.org/v104/Core/docs/Part3/8.57/