class Salesterm(EntityType):

    described_by_test = SubjectRelation('File', cardinality='1*', composite='subject')

    amount = Int(constraints=[IntervalBoundConstraint(0, 100)])

class tags(RelationDefinition):

    subject = 'Tag'

class checked_by(RelationType):

    subject = 'BlogEntry'

    cardinality = '?*'

    permissions = {

        'add': ('managers',),

        'read': ('managers', 'users'),

        'delete': ('managers',),

        }