This expressions lets one register participants directly from a process

              pdef = Ruote.define do
                registerp 'alpha', :class => 'MyParticipant', :target => 'mail'
                  # register participant named 'alpha' with the given class
                  # and some attributes
                registerp /^user_.+/, :class => 'MyParticipant'
                registerp :regex => '^user_.+', :class => 'MyParticipant'
                  # register participant with a given regular expression
                registerp 'admin', :class => 'MyParticipant', :position => -2
                  # register participant 'admin' as second to last in participant list

Participant info can be given as attributes to the expression (see code
above) or via the workitem.

              pdef = Ruote.define do
                registerp :participant => 'participant'
                  # participant info is found in the field 'participant'
                registerp :participants => 'participants'
                  # an array of participant info is found in the field 'participants'

The expression ‘unregisterp’ can be used to remove participants from the
participant list.