DTrace describes interfaces using a triplet of attributes consisting of two stability levels and a dependency class. By convention, the interface attributes are written in the following order, separated by slashes:
name-stability / data-stability / dependency-class
The name stability of an interface describes the stability level associated with its name as it appears in your D program or on the dtrace command. For example, the execname D variable is a Stable name.
The data stability of an interface is distinct from the stability associated with the interface name. This stability level describes the commitment to maintain the data formats used by the interface and any associated data semantics.
The dependency class of an interface is distinct from its name and data stability, and describes whether the interface is specific to the current operating platform or microprocessor.
DTrace and the D compiler track the stability attributes for all of the DTrace interface entities, including providers, probe descriptions, D variables, D functions, types, and program statements themselves. Notice that all three values can vary independently. For example, the curthread D variable has Stable/Private/Common attributes: the variable name is Stable and is common to all Oracle Solaris operating platforms, but this variable provides access to a Private data format that is an artifact of the Oracle Solaris kernel implementation. Most D variables are provided with Stable/Stable/Common attributes, as are the variables you define.