Webel: SysML: SE: Terminology: '«logical» handler' is used for a specific kind of «logical» subsystem (aka 'conceptual subsystem') that is a SPECIFIC collaboration of parts that handle one Activity usage in a higher level «whitebox» Activity.

The Webel recipe for pragmatic SE with SysML uses the specific term logical handler for a logical subsystem (aka conceptual subsystem) Block that handles a collaboration for one, and one only, Activity usage within a «whitebox» drill-down (ultimately from a «scenario» Activity that is at «blackbox» level).

The job of a logical handler Block is to represent one specific collaboration of parts, which may be already for design level blocks, or may themselves be logical handlers for another logical layer for very complex systems.

Think of logical handler as a subset of logical subsystem (which is a broader term that might not just serve one purpose).