SAREF4SYST is a generic extension of SAREF that defines ontology patterns which can then be instantiated for different domains. SAREF4SYST defines Systems, Connections between systems, and Connection Points at which systems may be connected. These core concepts can be used generically to define the topology of features of interest, and are specialized for multiple domains. This ontology patterns can be instantiated for different domains. For example to describe zones inside a building (systems), that share a frontier (connections). SAREF4SYST has two main aims: on the one hand, to extend SAREF with the capacility or representing general topology of systems and how they are connected or interact, and on the other hand, to exemplify how ontology patterns may help to ensure an homogeneous structure of the overall SAREF ontology and speed up the development of extensions. SAREF4SYST is specified and published by ETSI in the TS 103 548 associated to this ontology file.