Users of modern programming languages, like Java, would feel easy with object-oriented features in Kermeta: classes, inheritance, exceptions, and even genericity.

// persons who write documents
class Writer {
    attribute name : kermeta::standard::String
}

// generic concept for every document
abstract class Document {
    reference author : Writer
    attribute text : kermeta::standard::String
}

// a "Document" from the real world
class Book inherits Document {}

// a specialized "Book"
class ChildBook inherits Book {
    attribute minimalAge : kermeta::standard::Integer
}

Such classes can be used for verifications:

// a specialized Exception
class AgeException inherits kermeta::exceptions::Exception {}

abstract class Reader {
    operation read(book : ChildBook) : Void is abstract
}

class Child inherits Reader {
    attribute age :  kermeta::standard::Integer
    operation initialize(age :  kermeta::standard::Integer) : Child is
    do
        self.age := age
        result := self // return self so we can chain this call directly after a new
    end
    // an action which triggers an Exception
    operation read(book : ChildBook) : Void is
    do
        if age < book.minimalAge then
            raise AgeException.new
        end
    end
}