Foundational ontologies are tools for knowledge representation at a general level. They introduce hierarchies of concepts and relationships between these concepts. Foundational ontologies provide a common base for building more specific domain ontologies, which describe knowledge in expert domains. Foundational ontologies formally define categories and relations, improving the consistency of domain ontologies and facilitating their integration and knowledge exchange. Foundational ontologies structure knowledge in a hierarchy where at a highest level are defined universal entities and individuals, which instantiate the previous ones, and continuants and occurents, depending on their persistence in time. They also propose a set of abstract relationships from which more specific ones can be derived to relate concepts. Different foundational ontologies have been developed, proposing different knowledge organisations. In geospatial science, an important aspect of ontologies is the representation of spatial regions and spatial relationships. Regions can be built as point-sets or from atomic regions that correspond to elementary geospatial entities. The former approach facilitates quantitative reasoning in geometrical spaces while the latter is more appropriate for qualitative reasoning and the definition of high-level relationships. However, the representation must take into account the perception of boundaries and the possible vagueness of the concepts.
This entry discusses and defines ethical critiques and GIS. It complements other GIS&T Body of Knowledge entries on Professional and Practical Ethics and Codes of Ethics for GIS Professionals. Critical ethics is presented as the attempt to provide a better understanding of data politics. Knowledge is never abstract or non-material. Spatial data, as a form of knowledge, may mask, conceal, disallow or disavow, even as it speaks, permits and claims. A critical ethics of GIS investigates this situated power-knowledge. Two concepts from educational pedagogy are suggested: threshold and troublesome knowledge. As we use and continue to learn GIS, these concepts may enrich our experience by usefully leading us astray. This points finally to how ethical critique is practical, empirical and political, rather than abstract or theoretical.