Сравните язык объектных ограничений - Object Constraint Language (OCL) и работу с коллекциями в Smalltalk:

  Company.allInstances->collect(employees->size)

  Company allInstances collect: [:each | each employees size]

  Contact.allInstances->first

  Contact allInstances first

  Company.allInstances->first.employees->includes(self)

  Company allInstances first employees includes: self

  Category.allInstances->select(name = 'business')->notEmpty

  (Category allInstances select: [:each| each name = 'business']) notEmpty

  Company.allInstances->reject(employees->size = 1)

  Company allInstances reject: [:each| each employees size = 1]