What are the obligations of an assessor and /or moderator?

Back in the dark ages - March 2013 - I wrote an article on understanding assessment. I later followed this with an article on understanding moderation. The assessor article can be found by following the link below....

www.skills-universe.com/profiles/blogs/understanding-assessment-and-the-role-of-the-assessor

My question now is - what are the obligations of an assessor and/or moderator????? In other words if the assessor and/or moderator do their work properly then what are their obligations in relation to the learners and to the provider???