Product development requires the ability to check design consistency, to verify design properties, and to answer questions about a design's possible implementations. These tasks require inference based on design knowledge. The inference depends on having a representation of the design that is sufficiently precise to capture the design's intended meaning. Description Logics are languages with a formal logical semantics that have been engineered for conceptual modeling. OWL 2 is a W3C standard based on Description Logic. For algorithms that use inference to be guaranteed to produce an answer to a question the design knowledge base must generate a decidable theory. While OWL 2 has a decidable formal semantics it does not provide the expressiveness needed to constrain the possible interpretations of a design to be the intuitively valid physical implementations. A Description Graph Extension to Description Logic can be used to enhance expressiveness and eliminate design models tha...