This year's Ontology Summit is titled "Ontology for Big Systems" and seeks to explore, identify and articulate how ontological methods can bring value to the various disciplines required to engineer a "big system." The term "big system" is intended to cover a large scope that includes many of the terms encountered in the media such as big data, complex techno-socio-economic systems, intelligent or smart systems, cloud computing, netcentricity and collective intelligence. Established disciplines that fall within the summit scope include (but not limited to) systems engineering, software engineering, information systems modelling, and data mining. The principal goal of the summit is to bring together and foster collaboration between the ontology community, systems community, and stakeholders of some of the "big systems." Together, the summit participants will exchange ideas on how ontological analysis and ontology engineering might make a difference, when applied in these "big systems." We will aim towards producing a series of recommendations describing how ontologies can create an impact; as well as providing illustrations where these techniques have been, or could be, applied in domains such as bioinformatics, electronic health records, intelligence, the smart electrical grid, manufacturing and supply chains, earth and environmental, e-science, cyberphysical systems and e-government.