the frontier of gis gis web services nadine alameh, global science & technology next generation...
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The Frontier of GISGIS Web Services
Nadine Alameh, Global Science & Technology
Next Generation of Community Statistical SystemsTampa, FloridaMarch 14, 2002
March 14, 2002
Evolution of GIS: From Stand-alone to Web Services
Stand-alone systems (workstations)
Data tightly integrated with system
Desktop mapping
Databases with spatial extensions, SDE
Embedabble GIS components
Web mapping
Unbundled GIS into autonomous services
Distributed and interoperable GIS
services
-Lower costs of PC-Faster processing
-Internet (html, cgi, java)-Client/Server-Middleware (Corba)
-Wireless and mobile computing-Internet technologies (eg.XML)-Role of GIS in Enterprises-Availability spatial data
March 14, 2002
Evolution of GIS: From Stand-alone to Web Services
Satellite imagery Variety of suppliers anddistributors
Availability of Spatial Data
Web mapping Push for interoperability
Internet
Integration of databases Push for components
Role of GIS in Enterprises
Location-basedwireless services Services for thin clientswith bandwidth constraints
Mobile & Wireless Techs
Push towards an infrastructureof distributed autonomousinteroperable GIS services
March 14, 2002
GIS Web Services
IWeb MappingService
Web FeatureService
PortrayalService
Web MappingService
BundledService
Address MatchService
Mobile Devices:Retrieve image
centered atcurrent location
Browsers:Retrieve several
overlayed imagesas one
Standardized Interfaces
Information Systems:Perform business analysis based
on customers’ geographicaldistribution
RegistryService
Web services are self-contained, self-describing, modular applications that can be published, located, and dynamically invoked across the web.
Applications can be dynamically assembled from multiple network-enabled web services for use by a variety of client applications.
March 14, 2002
GIS Web Services Architecture Lower the learning curve Share data and services more effectively
IWeb MappingService
Web FeatureService
PortrayalService
Web MappingService
BundledService
Address MatchService
Mobile Devices:Retrieve image
centered atcurrent location
Browsers:Retrieve several
overlayed imagesas one
Standardized Interfaces
Information Systems:Perform business analysis based
on customers’ geographicaldistribution
RegistryService
Cut system integration and deployment cost Learn, use/get and pay only for what you need
March 14, 2002
Service Chaining When a task needed by a client cannot be provided by a single service, but
rather by combining or pipelining results from several complementary services.
ReprojectionService
WebCoverage Service
Web
Coverage Service
PortrayalService
Portrayal service assembles
orthoimage from several imagery
services
Reprojection service reprojects
the image from one coordinate
system to another one
Vector Data
Provider Service
Vector data provider service
returns a certain layer at the
extent specified
Overlay
Service
Overlay service overlays the inputimage and the vector data and
sends the overlay to the client
To ClientWeb
Coverage Service
March 14, 2002
User-Defined Chaining Chaining is transparent: User defines and controls the order of execution of
the individual services.
Address Matching
OrthoImageryService
Re-projectionService
Client Catalog Service
Address Matching
OrthoImageryService
Re-projectionService
ClientCatalog Service
March 14, 2002
Aggregate Service Chaining is opaque: the services appear as a single service which
handles all coordination of the individual services behind the aggregate service. The user has no awareness that there is a set of services behind the aggregate service.
Address Matching
OrthoImageryService
Re-projectionService
Client
Catalog Service
Aggregate Service
March 14, 2002
Workflow-Managed Chaining Chaining is translucent (in between transparent and
opaque): execution of the chain is managed by a workflow service. User may select a chain of interest that is executed by the workflow service.
Client
Address Matching
OrthoImageryService
Re-projectionService
Workflow ServiceCatalog Service
March 14, 2002
Opportunities Portals for Community Statistics Field
Focus on providing specialized aggregate and workflow services Customize chains and combine services to meet community statistics
needs Sophisticated tools:
Tools for users to construct and customized their own chains Tools for finding the right services based on characteristics such as
service scope, performance, service/data quality, price Tools for constructing “optimal chains”: least expensive, minimum
number of constituent services, most accurate results, etc. Challenge
Sustainability of such a service-based architecture requires standards and well-defined interfaces for the underlying services
March 14, 2002
Current Status Web Services Technologies
WSDL for service description UDDI for service discovery SOAP for passing XML-encoded data IBM WSFL and MS XLANG for service composition and process
languages for orchestrating web services into larger-scale applications
OGC work Categorization of services: data services (WMS,WFS,WCS),
processing services, registry services Encodings: SLD, GML WMS/SLD/CPS set a precursor precedent for service chaining in
the web services environment