Local Spatial Data Infrastrutures
Based on a
Service-Oriented Architecture
Clodoveu Davis
Leonardo Lacerda Alves
PUC Minas
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Introduction
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There is demand for GIS in large
computational environments, with a large
number of users, spread over numerous
locations, and high volumes of data
Factors:
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The fast development of networking technology
and the Internet
The success of Web-based GIS
The wide applicability of mobile and ubiquitous
computing
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Introduction

Many challenges arise when someone
tries to share (geographic) information:
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Data format/data structure issues
Data quality issues
Content issues
Semantics
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Introduction
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Early solutions included
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Data translation tools
Offline data replication
“Negotiated” semantics through (poor)
metadata
This led to intensive data redundancy
and numerous updating/synchronization
problems
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Introduction

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Data sharing and exchange among
several organizations is hard to achieve
It involves at least
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A lot of political negotiation
Agreements on standards
Agreements on costs and cost sharing
Agreements on maintenance
....
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Introduction
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The impact of such data exchange and sharing efforts
is very positive
We need technology that can make such efforts pay off
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Easier data access
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Less maintenance and synchronization issues
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Semantics
Semantics
Data usage directly from the source, without translation or
replication
More applications
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Free access to base maps
Public services
Value-added services
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Our proposal
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Extension of the concept of Spatial Data
Infrastructures (SDI) to local data and
applications
Definition of the architecture and
creation of a local, intra-organizational,
service-oriented local SDI
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Most SDIs are national or regional in scope
Service-oriented architectures help with
interoperability issues
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A Brief History of
GeoData Sharing
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Spatial data transfer standards
Spatial data clearinghouses
Spatial data infrastructures
Geoportals
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Early GIS
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Dataset creation was really expensive
and complex
Redundant efforts were commonplace
Potential data providers were late
adopters of GIS technology
Incipient market of data conversion
services
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Spatial Data Transfer
Standards
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Only helpful with syntactic problems
Data sharing requires
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An offline semantics agreement, plus
Select-export-copy-translate-import, plus
Some luck
There are a number of proposed
standards, but none has achieved
widespread acceptance
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Spatial Data
Clearinghouses
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SD Clearinghouses have been described
as sites through which a number of
services related to spatial data can be
accessed
The emphasis on services is recent: this
concept has been initially implemented
as a means to obtain “off-the-shelf”
data
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Spatial Data
Clearinghouses
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A 2004 study on national SDCs showed
that there is a growing dissatisfaction
from users as to the functional
capabilities available
The study indicates that the focus
should be user- or application-oriented,
instead of data-oriented
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Spatial Data
Infrastructures
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Evolution from the clearinghouse perspective
“Infrastructure” implies that there should be
some sort of coordination for policy
formulation and implementation
US definition (NSDI):
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“technologies, policies, and people necessary to
promote sharing of geospatial data through all
levels of government, the private and non-profit
sectors, and the academic community”
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Spatial Data
Infrastructures

SDI objectives are similar to the ones
pertaining to other kinds of
infrastructure
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Fostering economic development by means
of a range of publicly-available,
multiple-use goods or services
This does not mean that the services are
free of charge: do not confuse “publiclyavailable” with “government-supported”
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Spatial Data
Infrastructures
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SDIs should
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Provide standardized access to data
Have multiple participants, in the role of
information services providers and/or users
Have a broad thematic scope
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Facilitate data sharing
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Spatial Data
Infrastructures
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Widespread adoption of Internet-based
tools allowed the creation of Web
portals to multiple geographic
information sources
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Geoportals
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Geoportals
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Geoportal
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Web site that presents an entry point to
geographic content on the Web
Includes tools for
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The discovery of information sources and
content
Online access to Web-based applications
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SDI vs. Geoportal
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SDI
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Confluence of several different geodata providers
Access through specific Web services
Requires a repository or catalog of available
services
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Metadata
Usage by applications
Geoportal
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An SDI encapsulated by a human-computer
interface
Should be considered a component of an SDI
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Catalog
Web
Service
Publish
metadata
Geoportal
Services
request
SDI
Data
response
Discovery
Services
request
Search
Software
Client
Data
response
Data
response
Services
request
Human
User
Services
and Data
Catalog
GI Service
Provider
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Service-based Distributed
Systems Architecture
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Service-oriented architecture (SOA)
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Involves service providers, service
aggegators and service users
Users may be human or software clients
Available services are listed in directories
by providers
Aggregators design compositions of rules
based on primary services
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SOA
Web Services
Directory
Publish
Discover / Select
Web Service
User
Bind
Web Service
Provider
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OWS vs WS
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There is currently some confusion
between OGC Web services (OWS) and
W3C Web services (WS)
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OWS do not necessarily use the usual W3C
standards, including SOAP and WSDL
Instead of UDDI, OWS propose the use of
catalog services
OWS have a particular interface for binding
OWS use GML, and not plain XML
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OWS vs WS
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The OGC has specified a range of basic Web
services
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Web
Web
Web
Web
Web
Web
Web
Feature Service
Coverage Service
Map Service
Gazetteer Service
Registry Service/OpenGIS Catalog Service
Coordinate Transformation Service
Terrain Service
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Local SDI
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Most SDI development efforts focus on
the usual activities of national mapping
agencies, as the usual providers of
basic mapping data
The richness of local GIS applications
indicates that SDIs focused on local
data can also be important
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Local SDI
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Motivation
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The large number of actors involved in spatial
activities in urban areas
The wide variety and high detail level of
information classes involved in urban applications
The potential for fostering new applications on
commercially interesting subjects
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Location-based services
Personal routing
Convenience shopping
...
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Local SDI
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A local SDI and an urban GIS are very
different
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SDI: widely-available, general-use data,
accessible through services
GIS: organizational tool, built and operated
around a definite set of goals
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Local SDI
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An urban GIS (maintained by the local
government) may or may not become
an SDI, depending on how freely the
government distributes its information,
and on how well other urban data
providers are integrated in the
maintenance effort
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Services of Interest
for a Local SDI
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Basemap
Personal location
Geocoding/address recognition and location
Routing service
Public transportation system
Public services
Private services
Emergency services
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Services of Interest
for a Local SDI
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The proposed services are rather different
from the ones specified for NSDIs
It should be possible to chain these services
to generate more complete or integrated
services
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Value-added commercial services based on public
data
Public information of commercial interest available
through a fee
Coordination of efforts during emergencies and
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natural disasters
Conclusions
and Future Work
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This is a work in progress
We are currently working to create a
prototyping environment for Web
services and SOA
An undergoing project on geocoding is
being reconfigured to work under Web
services
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Conclusions
and Future Work
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Our goals include
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Develop a better understanding of the SDI
approach
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Including performance, privacy, and security concerns
Develop a method for the design and
implementation of WS/OWS for the SDI
Design means to publish metadata on services
Study the architectural possibilities for chained
Web services
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Mobile GIS applications
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[email protected]
[email protected]
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