RDF aims at being the universal abstract data model for structured data on the Web. However, the vast majority of web services consume and expose non-RDF data, and it is unlikely that all these services be converted to RDF one day. This is especially true in the Web of Things, as most RDF formats are textual while constrained devices prefer to consume and expose data in binary formats. In this paper, we propose an approach to make these services and things reach semantic interoperability, while letting them the freedom to use their prefered formats. Our approach is rooted in the Web architecture principles and the Web of linked data principles, and relies on the definition of RDF presentations. Supposing a RDF presentation is identified by a IRI and dereferenceable on the Web, we discuss what it takes for a client/ server to be able to discover how a message content can be interpreted as RDF, generated from RDF, or validated. We propose practical solutions to direct RDF presentation discovery and negotiation. Using these principles, we show how existing services and things can be made interoperable at low cost on the Semantic Web