This expression applies a filter to the workitem used by the process segment nested within it.

    class TestFilter48a0 < ProcessDefinition
        sequence do

            set :field => "readable", :value => "bible"
            set :field => "writable", :value => "sand"
            set :field => "randw", :value => "notebook"
            set :field => "hidden", :value => "playboy"

            alice

            filter :name => "filter0" do
                sequence do
                    bob
                    charly
                end
            end

            doug
        end

        filter_definition :name => "filter0" do
            field :regex => "readable", :permissions => "r"
            field :regex => "writable", :permissions => "w"
            field :regex => "randw", :permissions => "rw"
            field :regex => "hidden", :permissions => ""
        end
    end

In this example, the filter ‘filter0’ is applied upon entering bob and charly‘s sequence.

Please note that the filter will not be enforced between bob and charly, it is enforced just before entering the sequence and just after leaving it.

Note also that the ParticipantExpression accepts a ‘filter’ attribute, thus :

    <filter name="filter0">
        <participant ref="toto" />
    </filter>

can be simplified to :

    <participant ref="toto" filter="filter0" />