Global Positioning System Reference
In-Depth Information
Design and Implementation of SDWs
SDWs relay on the concept of spatial dimensions and measures. Three
types of spatial dimensions based on the spatial references of the hierarchy
members were proposed (Stefanovic et al. 2000; Rivest et al. 2001): non-
spatial (the usual conventional hierarchy), spatial-to-non-spatial (a level has
a spatial representation that rolls up to a non-spatial representation), and
fully spatial (all hierarchy levels are spatial). Furthermore, spatial measures
were classifi ed as the collection of pointers to spatial objects (Stefanovic et al.
2000; Rivest et al. 2001), as spatial objects themselves (i.e., their geometries),
or calculated using spatial operators, e.g., area or length (Rivest et al.
2001). Many authors rely on these defi nitions (e.g., Baltzer 2011; Glorio and
Trujillo 2008; Gómez et al. 2009a; Malinowski and Zimányi 2008; Times et
al. 2008) or propose some modifi cations. For example, Fidalgo et al. (2004)
introduced a GeoDWFrame only with spatial dimensions that were created,
in a rather complex manner, from spatial measures. Later on, this model was
extended to include spatial measures (Silva, Times et al. 2008). Bimonte et
al. (2005; 2006) and Damiani and Spaccapietra (2006) looked for symmetry
in defi ning spatial dimensions and measures, allowing the latter to include
spatial measures represented at different levels of granularity, i.e., forming
hierarchies. Shekhar and Chawla (2003), on basis of the classifi cation used
for non-spatial data, presented a classifi cation and examples of various types
of spatial measures. Jensen et al. (2004) extended their model by allowing
partial containment relationships for spatial members of lower hierarchy
level in relation to its parent level, while Malinowski and Zimányi (2008)
referred to different types of spatial hierarchies.
To the best of our knowledge, very few conceptual multidimensional
models with spatial support have been proposed (e.g., Aguila et al. 2011;
Bimonte et al. 2005; Damiani and Spaccapietra 2006; Glorio and Trujillo
2008; Jensen et al. 2004; Malinowski and Zimányi 2008; Pourabbas and
Rafanelli 2002; Times et al. 2008). These models, especially those that
included a graphical interface, could help implementers to better represent
user requirements and implement underlying structures more adequately,
since they could indicate which levels or hierarchies are shared, evidence
the aspect of measure additivity, or distinguish different kinds of spatial
hierarchies. However, even though some of the proposed solutions may
represent the multidimensional elements adequately, a systematic analysis
is still missing to determine whether all these elements are necessary in
real-life applications or whether some are omitted. In particular, not only
typical scenarios of the DWs representing administrative divisions as spatial
dimensions (as the ones that we use in this chapter), but also other kinds
of scenarios should be considered. For example, is the multidimensional
model adequate for implementing SDWs and SOLAP that consider spatial
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