This paper discusses the reuse of software components for describing and
implementing various schedulers.
We advocate the design of a generic scheduler
based on object-oriented methodology
(namely Smalltalk-80)\footnote{
	Smalltalk-80 is a trade mark of Parc Place Systems.}
in order to obtain optimal expressivity
and reuse.
It may be instantiated to match various scheduling policies.
This is achieved by defining new scheduler subclasses.
Scheduling primitives are proposed as building blocks to be combined
to define scheduling policies.
Some virtual methods represent the semantics of electing
current processes
and may be customized accordingly.

This scheduler has been primarily developed for
Actalk, a testbed for actor languages integrated into Smalltalk-80\footnote{
	Actalk \cite{Briot:Actalk:Ecoop:89} stands for 
	{\em act}ors in Small{\em talk}-80.},
to ease the prototyping of scheduling policies for actors.
It proved very useful for specifying various scheduling policies
for actors (like for instance in the Actor computation model
where there are at least two levels of concurrency:
inter-object and intra-object).

In this paper, we first present the goal of time-sharing algorithms.
Then we discuss the goals and motivations leading to the generic scheduler.
We then describe its architecture,
how it collaborates with the standard scheduler,
and the genericity and openness of its design.
We shortly discuss its implementation,
focusing on some use of reflective techniques in order to open-up
the fixed connection between the Smalltalk-80 virtual machine and the
standard scheduler.
We then shortly survey how it can be used to implement
step by step various scheduling policies.
We then conclude by summarizing how the full use of object-oriented
techniques allows the genericity of our scheduler,
and by comparing to related work.