This knowledge area deals with representation of formalized spatial and spatio-temporal reality through data models and the translation of these data models into data structures that are capable of being implemented within a computational environment (i.e., within a GIS or more likely within a spatial database). Data modelling is a crucial issue as it defines the content of a spatial database and usefulness of these content (data) for certain applications. Data Modelling is performed using system neutral languages like UML (or more seldom ER-diagrams). These conceptual models have to be transferred to logical models (i.e. tables of a database). Data is stored in spatial databases which are normally organized in an object relational way. For certain types of data specific databases are used, like triple stores, NoSQL DBs, Array DBs etc. For data modelling quite a number of ISO standards are available for deriving the conceptual model as well as for rules for application schemas, spatial schemas, temporal schemas, Quality principles, encoding, 3D modelling (CityGML) etc. Data models provide the means for formalizing the spatio-temporal conceptualizations. Examples of spatial data model types are discrete (object-based), continuous (location-based), dynamic, and probabilistic. Mastery of the objectives presented in this knowledge area require knowledge and skills presented in the bodies of knowledge of allied fields, including computer science (ACM/IEEE-CS Joint Task Force, 2001) and information systems (Gorgone & Gray, 2000; Gorgone & others, 2002).