Creating and Validating Object-Oriented Geographic Data Models: Modeling Flow within GIS

Abstract

Object‐oriented geographic data models provide an organizational scheme to associate domain specific meaning to primitive GIS elements like points, polylines, and polygons. Although use of data models is widespread in the GIS community, the design process is not necessarily obvious and often ad hoc. This article outlines a procedure for the creation and validation of geographic data models through the examination and distillation of use cases. As an example, the article follows the development of a data model for the spatial concept of flow. Flow, the collective movements of people, materials, or ideas, is a common driver of geographic change, not generally supported by functionality within contemporary GIS, and an abstract dynamic entity that would presumably be difficult to model. Model design was facilitated through the distillation of flow cases of tabular human migration data, Minard's map of Napoleon's march on Moscow, and stream channel routes in a karst watershed. Unified Modeling Language diagrams are created for each case and the models' commonalities combined to yield a generic data model. As a means of validation, each use case was instantiated with the generic model and tested to re‐create the fundamental components of flow and address predefined typical queries.

A Conceptual Poverty Mapping Data Model

“…From a pragmatic GIS perspective, the database framework offers a mechanism to add meaning to primitive GIS elements such as points, polylines, and polygons, relate their attributes, facilitate data collection and sharing, and build analytical and representation functionality. Sometimes, it happens that some order and relationships identified in the data model may be previously unrealized (Glennon 2010).…”

“…It is important to note that the analysis possible in a GIS is dependent on the mode of data modeling and structuring in the database. Throughout the model creation process, the designer should consider the typical queries the model should be able to answer (Glennon 2010).…”

“…Data modeling is required to better capture the components, processes, and meanings of poverty assessment as with any other geographic phenomenon, and translating the knowledge into a GIS (Glennon 2010). Already, about 32 different industry‐specific ArcGIS data models have been designed and implemented.…”

“…2009). Examples of spatial data modeling applications are flow modeling within GIS (Glennon 2010), land administration domain model (ISO 2010, Uitermark et al. 2010), hydrological/watershed modeling (Bollaert 2006, Gosain et al.…”

Towards Geodesign: Repurposing Cartography and GIS?

“…Such flows occur between pairs of features (origins and destinations), are not independent properties of either, and therefore cannot be displayed by symbolizing either feature alone, or even in combination. Lines might be drawn to connect origins and destinations, and appropriately symbolized, but in many cases the actual path of flow is not known (Glennon 2010), and a large number of such lines can render the map unreadable. In the previous section, this type of information was characterized as an association class in the objectoriented paradigm.…”