Interoperability is a core idea of Industry 4.0. For this purpose, components can already be semantically described and uniformly controlled via standards such as the Asset Administration Shell and OPC UA. To enable self-optimizing production systems, more knowledge from further data sources must be attached in a machine-readable form, and queried flexibly by intelligent, autonomous systems. The Linked Factory provides a suitable technology for this and establishes semantic interoperability on the shopfloor.