GLOSSARY - Mobility Data - page 364

privacy: The fact that it is impossible to discover the identity of a person on the basis of
the stored data, and that the personal sensitive information is protected from unauthorized
disclosure.
privacy by design: The approach of embedding privacy protection into the design, oper-
ation, and management of information processing technologies and systems.
privacy-enhancing technologies: Information and communication technologies for the
protection of information privacy . They are also referred to as privacy-preserving
technologies.
privacy personalization: Users' preferences about the requested type and level of privacy .
probabilistic spatial object: A spatial object whose extent is represented by a probability
(or density) function determining the probability that a given point be inside the extent of
the object. The uncertainty is due to the lack of knowledge, as in the case of the area of sea
covered by oil in case of an oil spill at a given position. This is to be contrasted with fuzzy
and vague spatial objects .
quasi-identifier: One or several attributes that from a pragmatic viewpoint (possibly with
the use of an external source) can be used to identify a person (or a small set of persons)
within the data set at hand. An example is zip code and birth date. This is to be contrasted
with identifier .
raw data: Data as captured by the sensing devices and transmitted to the receiver. It is a
sequence of spatio-temporal positions .
raw trajectory: A trajectory that holds only raw data . Antonym: semantic trajectory .
segmented trajectory: A semantic representation of a trajectory that segments the trajec-
tory into episodes , on the basis of the value of a given expression computed on the attributes
of the spatio-temporal positions . For instance, a trajectory may be segmented into stop and
move episodes on the basis of the instant stillness or speed.
semantic trajectory: A trajectory for which semantic information has been recorded:
geo-objects, events, semantic annotations. Antonym: raw trajectory .
sensitive information: Personal data, such as medical or salary data, that should not be
disclosed in association to the person's identity. It is also referred to as private information.
sliced representation: A representation for time-dependent types using a discrete model .
In this representation, a trajectory is split into slices defined by disjoint time intervals. The
trajectory within the slice is represented by a simple function (e.g., a straight line).
sound trajectory: A trajectory that has been preprocessed, making it clean (i.e., without
noise), accurate (i.e., map matched ), and possibly compact (i.e., compressed ).
space-time cube (STC): A visual representation of space and time as a three-dimensional
cube in which two dimensions represent space and one dimension represents time.
In an STC, spatio-temporal positions are represented as points and trajectories as
lines.
space-time prism: The set of all spatio-temporal points that can be reached by a moving
object given a maximum possible speed and starting and ending spatio-temporal points.
A space-time prism can represent the uncertainty about the position of a moving object
between two known (measured) positions.
sparsely sampled movement data: Data about spatial positions of moving objects where
the positions between the measurements cannot be reliably reconstructed by means of
interpolation , map matching , or other methods, due to too large time intervals between the
measurements. An example is the positions of mobile phone calls.