The simplest workitem store possible, gathers the workitem in a hash (this class is an extension of Hash).

Some examples :

    engine.register_participant(:alice, OpenWFE::HashParticipant)
    engine.register_participant("bob", OpenWFE::HashParticipant)

    hp = engine.register_participant(:charly, OpenWFE::HashParticipant)
    #...
    puts "there are currently #{hp.size} workitems for Charly"

    hp = OpenWFE::HashParticipant.new
    engine.register_participant("debbie", hp)