A B S T R A C TOne of the central problems in creating information management solutions for precision dairy farming is integration and interpretation of heterogeneous data coming from different equipment and data sources. Establishing a unifying data model is recognized as a cornerstone to such solutions. Here, the challenge lies both in agreeing on a common information context, and in selecting appropriate model representations, model query and update techniques, which guarantee model extensibility. While already existing ISOagriNET Data Dictionaries capture broad variety of the livestock and dairy farming concepts, the existing model representation technics cannot support efficient model extension. In this paper, we present our experience with using the representation and query standards and tools of the Semantic Web, endorsed by the World Wide Web Consortium (W3C), in particular the Resource Description Framework (RDF), the Web Ontology Language (OWL), and the SPARQL query standard, to encode and manipulate the dairy farming domain knowledge in a form of the Dairy Farming Ontology (DFO). Within the research project agriOpenLink the DFO has been created in two phases. The first phase focused on using the Semantic Web tools to facilitate easy encoding and manipulation of the dairy farming domain knowledge and the platform operational data models. The second phase focused on translating ISOagriNET Data Dictionaries into their semantic representations. Resulting DFO is maintained in a semantic repository, and it presents a knowledge graph and as integration backbone for the agriOpenLink decision support platform.