@inproceedings {INPROC-2010-81,
author = {Ralph Lange and Frank D{\"u}rr and Kurt Rothermel},
title = {{Indexing Source Descriptions based on Defined Classes}},
booktitle = {Proceedings of the 14th International Database Engineering and Applications Symposium (IDEAS '10). Montreal, QC, Canada. August 2010},
publisher = {ACM},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
pages = {245--256},
type = {Konferenz-Beitrag},
month = {August},
year = {2010},
keywords = {heterogeneous information systems; source descriptions; indexing of source descriptions; defined classes; tree-based index structure},
language = {Englisch},
cr-category = {H.2.5 Heterogeneous Databases,
H.3.3 Information Search and Retrieval},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2010-81/INPROC-2010-81.pdf,
http://doi.acm.org/10.1145/1866480.1866514},
contact = {ralph.lange@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Scaling heterogeneous information systems (HIS) to thousands of sources poses
particular challenges to source discovery. It requires a powerful formalism for
describing the contents of the sources in a concise manner and for formulating
compatible queries as well as a suitable structure for indexing and retrieving
the source descriptions efficiently.
We propose an extended logic-based description formalism for large-scale HIS
with structured sources and a shared ontology. The formalism refines existing
approaches that describe the sources by constraints on the attribute value
ranges in several ways: It allows for complex, nested descriptions based on
defined classes. It supports alternative descriptions to express that a source
may be discovered by different combinations of constraints. Finally, it allows
to adjust between positive matching, similar to keyword-based discovery, and
negative matching, as used in existing logic-based approaches.
We further propose the SDC-Tree for indexing such source descriptions. To allow
for efficient discovery, the SDC-Tree features multidimensional indexing
capabilities for the different attributes and the IS-A hierarchy of the shared
ontology, but also incorporates the existence or absence of constraints. For
this purpose, it supports three different types of node split operations which
exploit the expressiveness of the description formalism. Therefore, we also
propose a generic split algorithm which can be used with arbitrary ontologies.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2010-81&engl=0}
}
@inproceedings {INPROC-2010-15,
author = {Ralph Lange and Frank D{\"u}rr and Kurt Rothermel},
title = {{Efficient Tracking of Moving Objects using Generic Remote Trajectory Simplification (Demo Paper)}},
booktitle = {Proceedings of the 8th IEEE International Conference on Pervasive Computing and Communications Workshops (PerCom Workshops '10). Mannheim, Germany. March 2010},
publisher = {IEEE Computer Society},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
pages = {829--831},
type = {Workshop-Beitrag},
month = {M{\"a}rz},
year = {2010},
keywords = {Remote trajectory simplification; tracking; dead reckoning; moving objects database; MOD; line simplification},
language = {Englisch},
cr-category = {H.2.8 Database Applications},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2010-15/INPROC-2010-15.pdf,
http://dx.doi.org/10.1109/PERCOMW.2010.5470553},
contact = {ralph.lange@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Position information of moving objects plays a vital role in many pervasive
applications. Therefore, moving objects databases (MODs), which can manage
trajectory data of a number objects, are used in many pervasive systems. A
crucial problem with MODs is how to efficiently track a remote object's
trajectory in real-time, i.e. how to continuously report the sensed trajectory
data to the MOD with minimal effort. For this purpose, we present a
prototypical implementation of the Generic Remote Trajectory Simplification
(GRTS) protocol, which optimizes storage consumption, processing, and
communication costs. Our prototypical system includes a fully functional MOD as
well as map-based mobile applications for subnotebooks and smartphones to
illustrate the functioning of GRTS.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2010-15&engl=0}
}
@inproceedings {INPROC-2009-51,
author = {Ralph Lange and Harald Weinschrott and Lars Geiger and Andre Blessing and Frank D{\"u}rr and Kurt Rothermel and Hinrich Sch{\"u}tze},
title = {{On a Generic Uncertainty Model for Position Information}},
booktitle = {Proceedings of the 1st International Workshop on Quality of Context},
publisher = {Springer},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
pages = {1--12},
type = {Workshop-Beitrag},
month = {Juni},
year = {2009},
keywords = {data uncertainty; position information; position accuracy; spatial queries},
language = {Englisch},
cr-category = {H.2.8 Database Applications},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2009-51/INPROC-2009-51.pdf,
http://www.springerlink.com/content/85450711831008k0/},
contact = {ralph.lange@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Maschinelle Sprachverarbeitung;
Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Position information of moving as well as stationary objects is generally
subject to uncertainties due to inherent measuring errors of positioning
technologies, explicit tolerances of position update protocols, and
approximations by interpolation algorithms. There exist a variety of approaches
for specifying these uncertainties by mathematical uncertainty models such as
tolerance regions or the Dilution of Precision (DOP) values of GPS. In this
paper we propose a principled generic uncertainty model that integrates the
different approaches and derive a comprehensive query interface for processing
spatial queries on uncertain position information of different sources based on
this model. Finally, we show how to implement our approach with prevalent
existing uncertainty models.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2009-51&engl=0}
}
@inproceedings {INPROC-2009-07,
author = {Ralph Lange and Nazario Cipriani and Lars Geiger and Matthias Gro{\ss}mann and Harald Weinschrott and Andreas Brodt and Matthias Wieland and Stamatia Rizou and Kurt Rothermel},
title = {{Making the World Wide Space Happen: New Challenges for the Nexus Context Platform}},
booktitle = {Proceedings of the 7th Annual IEEE International Conference on Pervasive Computing and Communications (PerCom '09). Galveston, TX, USA. March 2009},
publisher = {IEEE Computer Society},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
pages = {1--4},
type = {Konferenz-Beitrag},
month = {M{\"a}rz},
year = {2009},
keywords = {Nexus; context; mobile context-aware applications; context-awareness; context management; World Wide Space; stream-processing; situation recognition; reasoning; workflows; quality of context},
language = {Englisch},
cr-category = {H.2.8 Database Applications,
H.3.4 Information Storage and Retrieval Systems and Software,
H.3.5 Online Information Services},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2009-07/INPROC-2009-07.pdf,
http://www.nexus.uni-stuttgart.de/,
http://dx.doi.org/10.1109/PERCOM.2009.4912782},
contact = {ralph.lange@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme;
Universit{\"a}t Stuttgart, Institut f{\"u}r Architektur von Anwendungssystemen;
Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Anwendersoftware},
abstract = {Context-aware applications rely on models of the physical world. Within the
Nexus project, we envision a World Wide Space which provides the conceptual and
technological framework for integrating and sharing such context models in an
open, global platform of context providers. In our ongoing research we tackle
important challenges in such a platform including distributed processing of
streamed context data, situation recognition by distributed reasoning,
efficient management of context data histories, and quality of context
information. In this paper we discuss our approach to cope with these
challenges and present an extended Nexus architecture.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2009-07&engl=0}
}
@inproceedings {INPROC-2009-06,
author = {Ralph Lange and Tobias Farrell and Frank D{\"u}rr and Kurt Rothermel},
title = {{Remote Real-Time Trajectory Simplification}},
booktitle = {Proceedings of the 7th Annual IEEE International Conference on Pervasive Computing and Communications (PerCom '09). Galveston, TX, USA. March 2009},
publisher = {IEEE Computer Society},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
pages = {1--10},
type = {Konferenz-Beitrag},
month = {M{\"a}rz},
year = {2009},
keywords = {Remote trajectory simplification; tracking; dead reckoning; moving objects database; MOD; line simplification},
language = {Englisch},
cr-category = {H.2.8 Database Applications},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2009-06/INPROC-2009-06.pdf,
http://dx.doi.org/10.1109/PERCOM.2009.4912767},
contact = {ralph.lange@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Moving objects databases (MODs) have been proposed for managing trajectory
data, an important kind of information for pervasive applications. To save
storage capacity, a MOD generally stores simplified trajectories only. A
simplified trajectory approximates the actual trajectory of the mobile object
according to a certain accuracy bound. In order to minimize the costs of
communicating position information between mobile object and MOD, the
trajectory simplification should be performed by the mobile object. To assure
that the MOD always has a valid simplified trajectory of the remote object, we
propose the generic remote trajectory simplification protocol (GRTS) allowing
for computing and managing a simplified trajectory in such a system in
real-time. We show how to combine GRTS with existing line simplification
algorithms for computing the simplified trajectory and analyze trade-offs
between the different algorithms. Our evaluations show that GRTS outperforms
the two existing approaches by a factor of two and more in terms of reduction
efficiency. Moreover, on average, the reduction efficiency of GRTS is only 12\%
worse compared to optimal offline simplification.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2009-06&engl=0}
}
@inproceedings {INPROC-2008-84,
author = {Ralph Lange and Frank D{\"u}rr and Kurt Rothermel},
title = {{Scalable Processing of Trajectory-Based Queries in Space-Partitioned Moving Objects Databases}},
booktitle = {Proceedings of the 16th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM GIS 2008)},
address = {Irvine, CA, USA},
publisher = {ACM},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
pages = {1--10},
type = {Konferenz-Beitrag},
month = {November},
year = {2008},
keywords = {spatio-temporal indexing; moving objects database; MOD; trajectory-based query; distributed query processing},
language = {Englisch},
cr-category = {H.2.8 Database Applications},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-84/INPROC-2008-84.pdf,
http://doi.acm.org/10.1145/1463434.1463474},
contact = {ralph.lange@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Space-partitioned Moving Objects Databases (SP-MODs) allow for the scalable,
distributed management of large sets of mobile objects' trajectories by
partitioning the trajectory data to a network of database servers. Processing a
spatio-temporal query q therefore requires efficiently routing q to the servers
storing the affected trajectory segments. With a coordinate-based query - like
a spatio-temporal range query - the relevant servers are directly determined by
the queried range. However, with trajectory-based queries - like retrieving the
distance covered by a certain object during a given time interval - the
relevant servers depend on actual movement of the queried object. Therefore,
efficient routing mechanisms for trajectory-based queries are an important
challenge in SP-MODs. In this paper, we present the Distributed Trajectory
Index (DTI) that allows for such efficient query routing by creating an overlay
network for each trajectory. We further present an enhanced index called DTI+S.
It accelerates the processing of queries on aggregates of dynamic attributes,
like the maximum speed during a time interval, by augmenting DTI with summaries
of trajectory segments. Our simulations with a network of 1000 database servers
show that DTI+S can reduce the overall processing time by more than 98\%.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-84&engl=0}
}
@inproceedings {INPROC-2008-37,
author = {Ralph Lange and Frank D{\"u}rr and Kurt Rothermel},
title = {{Online Trajectory Data Reduction using Connection-preserving Dead Reckoning}},
booktitle = {Proceedings of the Fifth Annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services: MobiQuitous '08; Dublin, Ireland, July 21-25, 2008},
publisher = {ICST},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
pages = {1--10},
type = {Konferenz-Beitrag},
month = {Juli},
year = {2008},
isbn = {978-963-9799-21-9},
keywords = {Online trajectory reduction; dead reckoning; MOD},
language = {Englisch},
cr-category = {H.2.8 Database Applications},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-37/INPROC-2008-37.pdf,
http://portal.acm.org/citation.cfm?id=1595044},
contact = {ralph.lange@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Moving objects databases (MODs) store objects’ trajectories by spatiotemporal
polylines that approximate the actual movements given by sequences of sensed
positions. Determining such a polyline with as few vertices as possible under
the constraint that it does not deviate by more than a certain accuracy bound
epsilon from the sensed positions is an algorithmic problem known as trajectory
reduction.
A specific challenge is online trajectory reduction, i.e. continuous reduction
with position sensing in realtime. This particularly is required for moving
objects with embedded position sensors whose movements are tracked and stored
by a remote MOD.
In this paper, we present Connection-preserving Dead Reckoning (CDR), a new
approach for online trajectory reduction. It outperforms the existing
approaches by 30 to 50\%. CDR requires the moving objects to temporally store
some of the previously sensed positions. Although the storage consumption of
CDR generally is small, it is not bounded. We therefore further present CDRM
whose storage allocation and execution time per position fix can be adjusted
and limited. Even with very limited storage allocations of less than 1 kB CDRM
outperforms the existing approach by 20 to 40\%.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-37&engl=0}
}
@inproceedings {INPROC-2008-110,
author = {Frank D{\"u}rr and Jonas Palauro and Lars Geiger and Ralph Lange and Kurt Rothermel},
title = {{Ein kontextbezogener Instant-Messaging-Dienst auf Basis des XMPP-Protokolls}},
booktitle = {5. GI/ITG KuVS Fachgespr{\"a}ch Ortsbezogene Anwendungen und Dienste. N{\"u}rnberg. September 2008},
address = {N{\"u}rnberg},
publisher = {Georg-Simon-Ohm-Hochschule N{\"u}rnberg},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
series = {Sonderdruck Schriftenreihe der Georg-Simon-Ohm-Hochschule N{\"u}rnberg},
volume = {42},
pages = {23--28},
type = {Workshop-Beitrag},
month = {September},
year = {2008},
issn = {1867-5433},
keywords = {Nexus; Instant-Messaging; Kontextbezug; context-awareness; Contextcast; XMPP},
language = {Deutsch},
cr-category = {H.4.3 Information Systems Applications Communications Applications},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-110/INPROC-2008-110.pdf,
http://www.nexus.uni-stuttgart.de/,
http://www.wireless-earth.de/fg_lbs/meeting_5/meeting_5.html},
contact = {frank.duerr@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Dieser Beitrag beschreibt die Verteilung kontextbezogener Informationen mittels
eines erweiterten Instant-Messaging-Dienstes. Dieser Dienst erm{\"o}glicht das
Senden von Nachrichten an alle Teilnehmer, die einen bestimmten Kontext
besitzen und sich z.B. an einem bestimmten Ort aufhalten oder bestimmte
Interessen besitzen. Als Basis dient das Extensible Messaging and Presence
Protokoll (XMPP) sowie ein XMPP-basierter Instant-Messaging-Dienst. Wir
beschreiben Protokoll- und Architekturerweiterungen f{\"u}r die Integration von
Kontextinformationen in das XMPP-Protokoll und die Server-Infrastruktur. Der
erweiterte Dienst unterst{\"u}tzt insbesondere die Server-seitige Filterung von
Nachrichten aufgrund von Kontextinformationen und erm{\"o}glicht dadurch die
effiziente Nachrichtenverteilung.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-110&engl=0}
}
@inproceedings {INPROC-2007-34,
author = {Tobias Farrell and Ralph Lange and Kurt Rothermel},
title = {{Energy-efficient Tracking of Mobile Objects with Early Distance-based Reporting}},
booktitle = {Proceedings of the Fourth Annual International Conference on Mobile and Ubiquitous Systems: Networking and Services (MobiQuitous 2007); Philadelphia, PA, USA, August 6-10, 2007},
publisher = {IEEE Press},
institution = {Universit{\"a}t Stuttgart : Sonderforschungsbereich SFB 627 (Nexus: Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme), Germany},
type = {Konferenz-Beitrag},
month = {August},
year = {2007},
isbn = {1-4244-1025-8},
doi = {10.1109/MOBIQ.2007.4450984},
language = {Englisch},
cr-category = {C.2 Computer-Communication Networks},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-34/INPROC-2007-34.pdf,
http://www.ieeexplore.ieee.org/xpls/abs_all.jsp?isnumber=4450969&arnumber=4450984},
contact = {Tobias.Farrell@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Many location-based systems rely on fine-grained tracking of mobile objects
that determine their own locations with sensing devices like GPS receivers. For
these objects, energy is a very valuable and limited resource. A distance-based
reporting protocol can be employed to reduce the energy they consume by sending
position updates. However, the energy required for position sensing has not
been considered in the past. In this paper, we study how the resulting energy
consumption from both sensing and update operations can be reduced for
distance-based reporting. We show that significant savings are achieved by
sending position updates earlier than actually required. For uniform movement,
we derive the minimal power consumption analytically. Subsequently, two novel
online heuristics are proposed that control the sending of position updates at
runtime. Their effectiveness is validated by extensive simulations.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-34&engl=0}
}
@article {ART-2012-21,
author = {Ralph Lange},
title = {{Scalable Management of Trajectories and Context Model Descriptions}},
journal = {PIK -- Praxis der Informationsverarbeitung und Kommunikation},
publisher = {De Gruyter},
volume = {35},
number = {4},
pages = {281--287},
type = {Artikel in Zeitschrift},
month = {November},
year = {2012},
doi = {10.1515/pik-2012-0041},
isbn = {ISSN 1865-8342},
keywords = {moving objects database; trajectory tracking; spatio-temporal indexing; heterogeneous information systems; defined classes},
language = {Englisch},
cr-category = {H.2.5 Heterogeneous Databases,
H.2.8 Database Applications,
H.3.3 Information Search and Retrieval},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/ART-2012-21/ART-2012-21.pdf},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {The ongoing proliferation of sensing technologies constitutes a huge potential
for context-aware computing. It allows selecting relevant information about our
physical environment from different sources and providers all over the globe. A
fundamental challenge is how to provide efficient access to these immense
amounts of distributed dynamic context information - particularly due to the
mobility of devices and other entities. To enable such access to current and
past position information about moving objects, we propose a family of
protocols (CDR, GRTS) for efficiently tracking a moving object's trajectory at
some remote database in real-time as well as a distributed indexing scheme
(DTI) for optimized access to trajectory data that is partitioned in space to
multiple database servers. For discovering context information that is relevant
for the situation of an application, we propose a powerful formalism for
describing context models in a concise manner and a tailored multidimensional
data structure (SDC-Tree) for retrieving relevant context models out of
potentially millions of descriptions.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2012-21&engl=0}
}
@article {ART-2012-18,
author = {Kurt Rothermel and Stephan Schnitzer and Ralph Lange and Frank D{\"u}rr and Tobias Farrell},
title = {{Context-aware and quality-aware algorithms for efficient mobile object management}},
journal = {Pervasive and Mobile Computing},
publisher = {Elsevier},
volume = {8},
number = {1},
pages = {131--146},
type = {Artikel in Zeitschrift},
month = {Februar},
year = {2012},
doi = {10.1016/j.pmcj.2011.04.009},
issn = {1574-1192},
keywords = {context-awareness; location management; mobile object tracking; range queries; efficiency},
language = {Englisch},
cr-category = {C.2 Computer-Communication Networks,
H.2.8 Database Applications},
ee = {http://dx.doi.org/10.1016/j.pmcj.2011.04.009},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {The management of positions of mobile objects is an essential prerequisite for
many context-aware systems such as advanced traffic management systems or
personal assistance systems. In this paper, we present two approaches for the
scalable tracking of mobile object trajectories and the efficient processing of
continuous spatial range queries, respectively. We show in detail how both
approaches utilize the basic concepts of accuracy relaxation and utilization of
context information, such as movement predictions, to minimize the number of
position updates, the size of trajectory data, and the number of
energy-consuming position sensing operations.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2012-18&engl=0}
}
@article {ART-2011-11,
author = {Ralph Lange and Frank D{\"u}rr and Kurt Rothermel},
title = {{Efficient real-time trajectory tracking}},
journal = {The VLDB Journal},
publisher = {Springer Berlin Heidelberg},
volume = {20},
number = {5},
pages = {671--694},
type = {Artikel in Zeitschrift},
month = {Oktober},
year = {2011},
doi = {10.1007/s00778-011-0237-7},
issn = {1066-8888},
keywords = {moving objects database; MOD; trajectory tracking; dead reckoning; line simplification},
language = {Englisch},
cr-category = {H.2.8 Database Applications},
ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/ART-2011-11/ART-2011-11.pdf,
http://dx.doi.org/10.1007/s00778-011-0237-7},
contact = {ralph.lange@ipvs.uni-stuttgart.de},
department = {Universit{\"a}t Stuttgart, Institut f{\"u}r Parallele und Verteilte Systeme, Verteilte Systeme},
abstract = {Moving objects databases (MOD) manage trajectory information of vehicles,
animals, and other mobile objects. A crucial problem is how to efficiently
track an object's trajectory in real-time, in particular if the trajectory data
is sensed at the mobile object and thus has to be communicated over a wireless
network. We propose a family of tracking protocols that allow trading the
communication cost and the amount of trajectory data stored at a MOD off
against the spatial accuracy. With each of these protocols, the MOD manages a
simplified trajectory that does not deviate by more than a certain accuracy
bound from the actual movement. Moreover, the different protocols enable
several trade-offs between computational costs, communication cost, and the
reduction in the trajectory data: Connection-Preserving Dead Reckoning
minimizes the communication cost using dead reckoning, a technique originally
designed for tracking an object's current position. Generic Remote Trajectory
Simplification (GRTS) further separates between tracking of the current
position and simplification of the past trajectory and can be realized with
different line simplification algorithms. For both protocols, we discuss how to
bound the space consumption and computing time at the moving object and thereby
present an effective compression technique to optimize the reduction
performance of real-time line simplification in general. Our evaluations with
hundreds of real GPS traces show that a realization of GRTS with a simple
simplification heuristic reaches 85-90\% of the best possible reduction rate,
given by retrospective offline simplification. A realization with the optimal
line simplification algorithm by Imai and Iri even reaches more than 97\% of the
best possible reduction rate.},
url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2011-11&engl=0}
}