Interchangeable GIS Components in Spatial Decision Support Systems

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Interchangeable GIS Components in Spatial
Decision Support Systems
Xueming Wu MS Thesis Defense

• Advisor Professor Steve Goddard

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Outline

• Motivation
• Background and Related Work
• Design and Implementation
• Evaluation
• Conclusion and Future Work

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Motivation

• A Spatial Decision Support System (SDSS) is
  created by integrating several software modules
  into a common computing framework.
• An agricultural SDSS might be comprised of
• climatic and economic models
• GIS software
• spatial data

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Motivation

• Coupling linkage of two stand-alone systems by
  data transfer
• information loss
• inconsistency
• Integration implementation of GIS and spatial
  analytical models upon a common data and method
  base
• closed and monolithic

Interoperability
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Hypothesis

• An open, interoperable SDSS that is independent
  of any GIS package can be built using component
  technology.

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Background Related Work
Geographic Information System (GIS)

• GIS is a computer system capable of assembling,
  storing, manipulating, and displaying
  geographically referenced information.
• Geographic Resources Analysis Support System
  (GRASS)
• ArcGIS

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• CORBA

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• DCOM

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• COM-CORBA Bridge

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Design Implementation

• Sub-hypothesis
• A GIS component can be designed and developed so
  that

• The implementation and complexity of the GIS
  component can be transparent to the other
  components of the SDSS.
• Any change to the GIS components will not affect
  the other components in the SDSS.
• The GIS component can adopt any of the major
  component models.
• The GIS component can be deployed on any major
  operating system.

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• SDSS Architecture

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• Component-based GIS Server Architecture

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Development of GIS Components Using GRASS

• Architecture of SDSS Using GRASS

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• Architecture of GIS Server (GRASS)

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• GRASSLib
• Wrap core functions and tools of GRASS into a
  shared library by
• Changing main() subroutine.
• Eliminating global variable and static variable.
• Freeing memory.

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Implementation Issues

Structure of GRASS database elements
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Management of Mapsets

• A mapset is used exclusively by a thread.
• Lock mechanism of mapsets
• if UNLOCK exists then mapset will be assigned.
• if LOCK exists then skip the mapset.
• rename UNLOCK to LOCK when assigning.
• rename LOCK to UNLOCK after execution

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LOCATION Management Projection Transformation

• Explicit approach
• directly process the coordinates
• apply to input parameters
• Implicit approach
• select LOCATION with the required projection
• apply to output of components
• no computing overhead
• more disk space
• possibility of data inconsistencies.

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Data Formats

• Uses the GRASS data format as native format
• Uses ASCII-based vector and raster formats for
  input and output
• Provides data conversion
• ESRI shapefiles
• Acrobat pdf
• jpeg
• gif

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Development of GIS Components Using ArcGIS

Architecture of SDSS Using ArcGIS
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Abstract Architecture of GIS Server (ArcGIS)

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COM-CORBA Bridge

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Detailed Architecture of GIS Server (ArcGIS)

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Post-processing of Output
//return type of CORBA component BinaryData_var
ret CORBAOctet buf //return type of COM
component struct ARC_BinaryData short
data long size struct ARC_BinaryData
arc_result //mapping returned result between
COM and CORBA components buf BinaryDataallocbu
f(arc_result.size) for (i 0 i lt
arc_result.size i) bufi
arc_result.datai ret new
BinaryData(arc_result.size, arc_result.size, buf
, 1) return ret._retn()

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Evaluation Test Bed

• National Agricultural Decision Support System

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• NADSS Test Bed

GIS Server
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• Evaluation GIS Components

• Reusability
• Interoperability
• Interchangeability

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• Reusability

• Crop Production Risk Analysis
• Soil Moisture Regime Probability
• Palmer Drought Severity Index
• Standardized Precipitation Index

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• Interoperability

• Data Formats
• ASCII-based vector and raster formats
• pdf, jpeg, gif and png files
• Existing GIS
• GRASS
• ArcGIS
• Component Model
• CORBA
• DCOM
• Deployment platform
• Sun OS
• Redhat Linux
• Windows 2000

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• Interchangeable

• Same functionality
• Same interfaces
• Can be integrated into NADSS

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• Conclusions

• Introduced a layered architecture.
• Presented the development of a set of GIS
  components based on GRASS.
• Described the implementation of a set of GIS
  components based on ArcGIS.
• Used NADSS as a test bed.
• Evaluated the component-based GIS servers.

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• Contribution

• Demonstrated that an open, interoperable SDSS
  can be built using component technology.
• Presented a component-oriented architecture and
  related technologies to build an open,
  interoperable SDSS.
• Demonstrated that a component-based GIS Server
  can be built from an existing GIS package.

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• Future Work

• Future Work
• Apply OpenGIS Consortiums (OGC) standards to
  our SDSS.
• Mix GIS components based on different existing
  GISs in one SDSS.

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• Acknowledgements

Dr. Steve Goddard Dr. Sharad Seth and Dr. Ashok
Samal Shifeng Zhang Ian Cottingham and Kun Lu my
colleagues, my friends, my family, and the
faculty and staff of CSE