[Rails] ActiveRecord on data integrity

["Luis G. Gómez"]

Hello all,

I'm fairly new to this so please excuse me if this sounds like a basic 
question.

Reading the docs on AR I see that I can create assosiations in my models 
but does this mean AR maintains data integrity?

Say, if I had:

class Project < ActiveRecord::Base
    belongs_to :portfolio
    has_one :project_manager
    has_many :milestones
    has_and_belongs_to_many :categories
end

...would AR errase a project's milestones if I errased the project that 
owns them?

Thank you.

LG