The first time I heard about a petition in BDSM was during my many talks with Sir about this lifestyle. Sir likes protocals and etiquette. So do i as it offers me a sense of order and direction. One of things Sir mentioned to me was that when the time came and I have decided that being his was what I wanted I would have to petition him to be in his service. I was like “petition” what in the world is that.
A petition in BDSM is something that the submissive provides to the dominant. It should detail the reason the submissive wants to be with the dominant, what the submissives offers in terms of service to the dominant and your goals in the relationship. This would be like a prenuptial agreement in vanilla terms.
Sir went to a demonstration given by Kim Attica at Capex this weekend and she gave a link to a site that she uses called iron rose library. I found some of the items at the library to be very interesting. Doing a search on my other favorite site wikipedia bought up some information as well.
So that being said a petition is not something that anyone should write lightly. It should be something well thought out. You are making a written commitment to someone and this should be taken just as serious as a verbal comittment.
mvs1esclave
The House of Void 
The iron rose library link does not work