@startuml
class Form {
    protected elements
    +render($indent = 0)
    +addElement(FormElement $element)
}

abstract class FormElement {
    +render($indent = 0)
}

class InputElement {
    +render($indent = 0)
}

class TextElement {
    +render($indent = 0)
}

FormElement <|.. TextElement
FormElement <|.. InputElement
FormElement <|.. Form
@enduml