K-Anonymity
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K-Anonymity Privacy Threats in Location-Based Services
Keyword Search Internet-Based Spatial Information Retrieval
K -Nearest Neighbor Query Nearest Neighbor Query
Knowledge Based Systems Decision Support Systems
Knowledge Representation, Spatial ROBERT R ASKIN Jet Propulsion Laboraty, California Institute of Technology, Pasadena, CA, USA Synonyms GeoOntologies; XML triple Definition The formal definition of knowledge can be elusive. We tend to recognize knowledge when we encounter it, but have greater difficulties in defining it. Knowledge can be distinguished from data and information [1]. Data are raw observations made through sensory or instrumental measurements. Spatial data typically consists of records of where something is located in space. Information is a summarized description of the data. In this transformation, the volume of the data decreases, but its density (value per unit) increases. Spatial information
might be a mathematical representation of how an attribute varies over geographic space. Knowledge is the next step in this chain – it includes a context for the ingested information. Knowledge implies that some background information is present, along with some means to build upon that information. Spatial knowledge is the understanding of where and why people or objects are located relative to one another. A GIS provides knowledge of the spatial domain through agreed upon representations of spatial coordinate systems, administrative boundaries, place names, etc. Community GIS data model extensions such as ArcHydro provide further enhancements to knowledge using hydrological concepts provided by that community. Formal representation of spatial knowledge differs from the corresponding representation of data, as it must capture both facts and context. The context corresponds roughly to the common sense learned knowledge that the brain develops over time. ontologies have emerged as an effective machine-readable language for capturing knowledge. An ontology is a description of concepts and how they relate to one another, typically expressed in an XML format. Main Text Geographers have long studied cognitive concepts of space – how people perceive space and how these perceptions relate to actual physical space. The resulting approximations of spatial relationships capture the process of summarization and contextualization of our knowledge capture processes. Spatial knowledge capture was integral to the early days of artificial intelligence in robotics applications. The key to making a robot functional and useful is to have it understand the nature of objects and obstacles it encounters in its path. More recently, geographers have encoded spatial cognitive knowledge directly into ontological frameworks [2,3]. An ontology is useful as a formal representation of knowledge that both humans and computers can process and append to. In the most common convention, the ontology
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