Software architectures for knowledge-based engineering often separate applications from their knowledge sources. We propose elements for a new standard for the resulting interface. The fully automatic transfer of knowledge would require a shared engineering ontology. We suggest something less ambitious, namely to make only part of the knowledge machine-intelligible, such as a number embedded in a rule. This proposal still requires a human to code the knowledge from the source into the application. However, it would allow the application to automatically handle some updates to the knowledge sources. We discuss the details of a formalism to describe the machine-intelligible part of the knowledge; we suggest some meta-data; and we clarify the relationship of the proposal to existing standards.