OPC Unified Architecture (UA) is a powerful and versatile platform for hosting information from a large variety of domains. In some cases, the domain-specific information models provide overlapping information, such as (i) different views on a specific entity or (ii) different levels of detail of a single entity. Emerging from a multi-disciplinary engineering process, these different views can stem from various tools that have been used to deal with that entity, or from different stages in an engineering process, e.g., from requirements engineering over system design and implementation to operations. In this work, we provide a small but expressive set of OPC UA reference types that unobtrusively allow the persistent instantiation of additional knowledge with respect to relations between OPC UA nodes. We will show the application of these reference types on the basis of a rendezvous of AutomationML and ISA-95 in an OPC UA server.