An ontology is a formal specification of a shared conceptualization. In the context of computer and information sciences, an ontology defines a set of representational primitives with which to model a domain of knowledge or discourse.

Ontologies are considered one of the pillars of the Semantic Web, although there exist many definitions.

Datasets that can be freely used, shared and built-on by anyone, anywhere, for any purpose.

This is the summary of the Open Definition which the Open Knowledge Foundation created in 2005 to provide both a succinct explanation and a detailed definition of open data

Source: Open Knowledge Foundation (OKNF). What is open?

Governing doctrine, which holds that citizens have the right to access the documents and proceedings of the government to allow for effective public oversight. In its broadest construction it opposes reason of state and other considerations, which have tended to legitimize extensive state secrecy.

An open licence is a way for the copyright holder (creator or other rightsholder) to grant the general public the legal permission to use their work. The applied open licence is usually indicated directly on the work and wherever the work is shared. As in the case of other licences, open licences do not imply a transfer of copyright or other intellectual property rights.

The way in which public administrations align their business processes, responsibilities and expectations to achieve commonly agreed and mutually beneficial goals.

ELISE Resources: The role of Organisational Interoperability in the context of Geospatial and Digital Government Transformation