Dynamic Interoperable GeoProcessing and Geosimulation - Scenarios

							 Dynamic Interoperable GeoProcessing and Geosimulation - Scenarios,
                  FRAmeworks, AND prototypes

                          Lars Bernard, Andreas Wytzisk & Ulrich Streit
                                    Institute for Geoinformatics
                                       University of Münster
                              Robert-Koch-Str. 26-28, 48 149 Münster
                            {bernard,wytzisk,streit}@ifgi.uni-muenster.de

Abstract
Standards to reach an interoperable geoservice architecture (OpenGIS) and a framework for
interoperable dynamic simulation (High Level Architecture) emerge to a more or less stable
state. This offers the chance to integrate these initiatives to support dynamic spatio-temporal
monitoring and simulation. This paper shows first steps towards an architecture design and
presents a scenario for a proof of concept.

1. Introduction

Taking the GI perspective, the discussion concerning systems to combine GIS and dynamic
simulation models mainly focuses on the required data models, query languages and
visualisation methods (Maxwell 1999, Peuquet 1999, Clarke et al. 2000, Uhlenküken and
Schmidt 2000). However, the ongoing development of GI-components to manage and visual-
ize temporal geodata is the first step towards setting up Dynamic GIS. The consequent next
step should involve tools to monitor and even manage simulated and real processes in space
and time. That way simulation is meant in a broader sense. It includes not only numerical
models but also data sources sending measurements continuously or user interactions with
the running system.

Application areas can be found for instance in transportation, telecommunication, environ-
mental simulations or risk management. Future GI science work is needed to define specifi-
cations for service architectures to enable the monitoring and the controlling of spatio-tem-
poral processes.

2. OpenGIS-HLA Integration

The objective of upcoming research in the field of geoprocessing is to evolve interoperability
standards to develop flexible and scalable controlling and simulation services. Current
OpenGIS specifications define GIS in a more or less static way (OGC 1999). Though time
can be handled as an additional attribute, its representation is not explicitly specified. Thus it
is impossible to model time-variant processes in a standardized interoperable way (Bernard
and Krüger 2000). Even most of the current research approaches to handle time in geodata
models are not meant to support time-variant processes.

In contrast the High Level Architecture (HLA), developed by the US department of defense
provides a framework for distributed time-variant simulation processes (DOD 1998). The
HLA became an IEEE standard and first civil prototypes exist, e.g. in the area of public
transportation (Schulze et al. 2000). But the HLA lacks in supporting spatial applications.


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Regarding this, the integration of these two initiatives to combine the ‘best of the two worlds’
becomes highly attractive.

2.1 Fundamentals of a common service model

The research is directed towards the design of a service architecture that integrates the OpenGIS
service architecture and the HLA as a common basement for the description, development
and execution of spatio-temporal services. Figure 1 shows a first approach towards an archi-
tecture design.




Figure 1. An OGC- and HLA-based architecture for interoperable spatio-temporal services

The proposed design tackles three major issues:

(1) Enabling the exchange of geoobjects - GeoFederate:

   The elementary geometric types, defined in the OpenGIS specification, must be described
   for the HLA compliant simulators (so called federates). This is done by declaring new
   HLA object classes using the HLA Object Model Templates (OMT). Appropriate encoding
   and decoding factories enable the HLA federates to exchange OGC compliant geoobjects
   between each other. This is realized by applying the Geo Markup Language (GML) to
   encode and decode geoobjects to bytestreams that are used by the HLA to interchange
   objects.

(2) Enabling the use of OGC services for HLA simulators - GeoClientFederate:

   By extending the HLA federate interface in a way that it is able to use OpenGIS compliant
   services we provide GeoClientFederates.

   The current OpenGIS service specification lacks a common service interface to describe
   the services in a generic manner. Therefore the implementation of a number of different


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  interfaces becomes necessary. However, the results of the ongoing web map testbed 2
  (WMT2, see http://www.opengis.org), especially the upcoming basic service model will
  offer a more generic solution. Thus we will be enabled to describe the capabilities of
  services using XML.

(3) Enabling the offer of HLA simulators as OGC services - GeoServiceFederate:

  Once having the ability to describe the capabilities of a OpenGIS compliant service in a
  generic way, we are also able to specify interfaces that describe HLA simulators as new
  OpenGIS services. Thus the simulators become part of the OpenGIS service infrastruc
  ture. We consider a HLA simulator to behave like a datastore, that is made accessible as a
  web feature service or a web coverage service. Queries and parameter settings can be
  encoded using an OGC compliant filter description.

3. A simulation scenario

The potential of this integration becomes particularly clear if the concept is applied to a
complex simulation scenario including real-time components. Such a scenario will be sketched
briefly in the following paragraph.

We consider an atmospheric dispersion model to simulate the hazards raised by an industrial
accident. Based upon recent weather data (temperature, air pressure, main wind direction,
precipitation, etc.) the simulation supplies the site specific contamination risk in the sur-
rounding area. The permanently updated dispersion forecast acts as an input parameter for an
emergency management tool. This tool automatically generates and updates an optimised
evacuation plan. Information about the effective traffic situation are also incorporated and
permanently updated. Evacuation instructions are sent using the short messaging service (SMS)
to the effected citizens.




Figure 2. An OGC/HLA based emergency management scenario.


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Lets have a look at the architecture. The dispersion simulation model is realized as a HLA
federation which consists of the dispersion simulator itself and a number of weather monitor-
ing federates supplying the simulation federate with current weather data. The dispersion
simulator is a GeoServiceFederate thus it is able to offer highly up-to-date dispersion prog-
noses as coverages in an OpenGIS compliant way. These informations are used by the evacu-
ation planning GeoClientFederate that also incorporates static street data and dynamic traffic
information offered by WebFeatureServices.

4. Conclusion and future work

After having started with the presented first ideas towards the integration of the OpenGIS
service architecture and the High Level Architecture the next working packages are:

- Refinement and detailed specification of the proposed architecture

- Implementation of these specifications for a proof of concept

Once having a running system it has to be reviewed whether the presented concept is just a
helpful integration of two complementary standards or if it is extending GIS in a way that it
enables not only the management of spatio-temporal data but also offers the chance to handle
dynamic processes.

References

Bernard, L. & T. Krüger, 2000. Integration of GIS and Spatio-Temporal Simulation Models. Transactions in GIS
4(3): 197-215.

Clarke, K., B. Parks & M. Crane, Eds., 2000. Special Issue: Selected Papers from the Fourth International
Conference on Integration Geographic Information Systems and Environmental Modeling (GIS/EM4). Transac-
tions in GIS 4(3).

DOD, 1998. High-Level Architecture, Rules, Version 1.3. U.S. Department of Defense. IEEE P1516/D3.

Maxwell, T., 1999. A Parsi-Model Approach to Modular Simulation. Environmental Modeling and Software 14:
511-517.

OGC, 1999. The OpenGIS Abstract Specification. http://www.opengis.org

Peuquet, D., 1999. Time in GIS and geographical databases. In: P. A. Longley, M. F. Goodchild, D. J. Maguire
& D. W. Rhind (Eds.). Geographical Information Systems - Principles and Technical Issues. New York, John
Wiley. 1: 91-103.

Schulze, T., S. Straßburger & U. Klein, 2000. Migration of HLA into Civil Domains: Solutions and Prototypes
for Transportation Applications. SIMULATION 73(5): 296-303.

Uhlenküken, C. & B. Schmidt, 2000. Visual Exploration of High-Dimensional Spatial Data: Requirements and
Deficits. Computers & Geosciences 26(2): 77-85.




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