Inheritance is a key technical feature of DITA, as it is inheritance that enables specialisation of information types.

In object-oriented programming, inheritance is a way to form new program module classes using classes that have already been defined. DITA is designed around the principle of inheritance. The DITA base content model shows that even the three base information types (concept, task and reference) evolve from the topic proto information type, and share a common base structure whose characteristics they inherit.

Information Type Content Model - Base

Evolution of base information types

This idea of inheritance continues down. A task's step element is based on topic's li element.

The DITA Language Reference records the inheritance of each element. For example, the step element's inheritance is shown as topic/li, indicating that a topic information type's li element is specialised to become task/step, a task information type's step element.

DITA's inheritance model makes it easy to specialise topics or special elements within topics. You only have to define how the element is different from its immediate ancestor.

This idea reminds us again of Darwinian theory.

Evolution of Man

Evolution of man and an information type