The document discusses the concept of knowledge double-articulation as a methodology for engineering ontologies. It explains that the meaning of a vocabulary should be doubly-articulated into a domain axiomatization and one or more application axiomatizations. The domain axiomatization characterizes the intended meaning of terms at the community level, while application axiomatizations focus on how the terms are useful for specific applications. This double-articulation makes ontologies more reusable, usable, and easier to integrate and maintain. Examples from customer complaint and library ontologies are provided to illustrate the concept.