Forum OpenACS Development: Re: Res: Callbacks in Workflow

Thanks for your help.  The last question  is:

Must all these callbacks be defined?
or only those that it is necessary implement?

<callback type="before-uninstall" proc="curriculum_central::install::package_uninstall"/>
<callback type="after-install" proc="curriculum_central::install::package_install"/>
<callback type="before-uninstantiate" proc="curriculum_central::install::package_uninstantiate"/>
<callback type="after-instantiate" proc="curriculum_central::install::package_instantiate"/>

thanks for a lot.