Semantrix: A Compressed Semantic Matrix
Nieves Brisaboa, Antonio Fariña, Gonzalo Navarro, and Tirso Rodeiro
We present a compact data structure to represent both the duration and length
of homogeneous fragments of trajectories from moving objects in a way that, as
a data warehouse, it
allows us to efficiently answer cumulative queries. The division of
trajectories into relevant
fragments has been studied in the literature under the topic of Semantic
Trajectories. In
this paper, we designed a data structure to compactly represent them and the
algorithms
to answer the more relevant queries. We experimentally evaluate our proposal
into the real
context of an enterprise with mobile workers (truck drivers) where we aim at
analyzing the
time they spend in different activities. To test our proposal under higher
stress conditions
we generated a huge amount of synthetic realistic trajectories and evaluated
our system
with those data to have a good idea about its space needs and its efficiency
when answering
different types of queries.