The explorer has some role based access, but I doubt that it is what you are looking for. I'd appreciate it if you do not just post some questionaire to et to a short list, but add some detail on why/how etc… Keep in mind that Activiti is not a full blown, one-stop shop fo all your b2b/workflow 'problems'. I should be part of a bigger solution, e.g. In combination with Alfresco, a SSO solution, b2b messaging (e.g. ebMS) etc…