# A Spatio-Temporal Building Exposure Database and Information Life-Cycle Management Solution
## 2 Exposure Data Management in Support of Disaster Risk Management
### Taxonomy  
Given the complex elements composing the exposure of the built human environment (for instance, the structural components of a building), a clearly defined taxonomy is essential in order to overcome possible misunderstandings amongst data collectors and analysts, especially at transnational and global scales. The preparation of a taxonomy involves the creation of an exhaustive and structured set of mutually exclusive and well-described attributes, which can be structured hierarchically or faceted and encoded in numeric or alphabetical codes [28]. A taxonomy suitable for describing exposure at large-scale should be international in scope, detailed, collapsible, extendable, user friendly, and suitable to describe different types of exposed assets with enough detail to match the requirement of the related vulnerability models [29]. Moreover, ideally an exposure model could accommodate structural and non-structural features relevant for different natural hazards, therefore setting the base for an efficient, integrated, multi-risk exposure modelling. The harmonization of information between taxonomies is of particular importance in order to be able to combine or compare data that have been collected about different inventories, or over different time periods, and which may potentially have involved different data collection methods and/or spatial units. Harmonization can be achieved by applying consistent standards and taxonomies across different data sets and by establishing look-up tables mapping the homologous categories of different taxonomies.  
Several taxonomies have been developed mainly in the field of earthquake engineering in order to classify and characterize building inventories in standardized and comparable ways. Widely used taxonomies that aim at describing the structural components of buildings include HAZUS [30], the European Macroseismic Scale 1998 (EMS-98) [31], Prompt Assessment of Global Earthquakes for Response (PAGER) [32], and the World Housing Encyclopedia [33]. A structural taxonomy is just one of several taxonomies that together contain all the relevant data about a particular exposed asset. Other (non-structural) taxonomies are used to encode further information, including non-structural features, occupancy, population, or economic values. A recently established structural taxonomy that also includes few non-structural attributes (e.g., occupancy) is the Global Earthquake Model (GEM) Building Taxonomy [29]. It follows the concept of a faceted taxonomy [34]. In comparison to hierarchical taxonomies, where the data are organized in a tree-like structure, the hierarchy of classes in faceted taxonomies is not fixed and can be changed. Faceted taxonomies allow information to be navigated along multiple paths corresponding to different arrangements of the facets and items in more than one dimension. Due to its clear and flexible structure, its complexity and comprehensiveness and the fact that it may also be applicable to hazards other than earthquakes, the GEM Building Taxonomy Version 2.0 was used as the basis to structure the taxonomy schema of the proposed database model.