1 research outputs found
A triangle-based logic for affine-invariant querying of spatial and spatio-temporal data
In spatial databases, incompatibilities often arise due to different choices
of origin or unit of measurement (e.g., centimeters versus inches). By
representing and querying the data in an affine-invariant manner, we can avoid
these incompatibilities.
In practice, spatial (resp., spatio-temporal) data is often represented as a
finite union of triangles (resp., moving triangles). As two arbitrary triangles
are equal up to a unique affinity of the plane, they seem perfect candidates as
basic units for an affine-invariant query language.
We propose a so-called "triangle logic", a query language that is
affine-generic and has triangles as basic elements. We show that this language
has the same expressive power as the affine-generic fragment of first-order
logic over the reals on triangle databases. We illustrate that the proposed
language is simple and intuitive. It can also serve as a first step towards a
"moving-triangle logic" for spatio-temporal data.Comment: 43 pages, 11 figure