June 9-11, 2004 Carleton University Ottawa Canada OGC in Open Source Products Tom Kralidis Jeff...
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Transcript of June 9-11, 2004 Carleton University Ottawa Canada OGC in Open Source Products Tom Kralidis Jeff...
June 9-11, 2004 • Carleton University • Ottawa • Canada
OGC in Open Source Products
Tom Kralidis
Jeff McKenna
Peter Pulsifer
Bart van den Eijnden
June 9-11, 2004 • Carleton University • Ottawa • Canada
June 9-11, 2004 • Carleton University • Ottawa • Canada
• Interoperability Overview
• Benefits of OGC in the Organization
• Examples / Demos
• OGC / Open Source Issues
• Comments/Questions/Discussion
June 9-11, 2004 • Carleton University • Ottawa • Canada
• Interoperability Overview
• Benefits of OGC in the Organization
• Examples / Demos
• OGC / Open Source Issues
• Comments/Questions/Discussion
Infrastructure
• Many pieces working independent of make, model
• Open interface– Can communicate with other things
• Transparent / Invisible
• Cooperative
• Distributed
The Distributed Approach
• Distributed Spatial Data infrastructure• Cost / Feasibility• One Source• Up-to-date Data• Data Management Issues• Less:
– Local storage space– redundant data
• How?– Web Services
Web Services
• Independent of– operating systems– programming languages– Organizations
• How?– non-proprietary data / messaging
standards• eXtensible Markup Language (XML)
Web Services
• Until recently everyone is developing in their own little world (metadata => data => applications)
• From functionality to interoperability• Internet is driving these changes: no net,
then little reason to interoperate• Being “open” is a strong selling point
– E.g. VCR cassettes: VHS vs. BETA– E.g. mix and match your home stereo
system components
Web Services- Benefits
• Lower software integration costs
• Maintaining legacy systems
• Using standards lowers IT costs of
collaboration with external partners,
vendors, clients
Web Services Architecture Approach
Applicationse.g., Transportation Planning, Climate Change Monitoring,
Site Assessment
Servicese.g., Metadata Service,
gazetteer service,Web Map Service
Datae.g., topographic, thematic, imagery,
toponymy, metadata
Users
OtherApplications
For Example…
A trip planning web site that calculates the best route between two cities
usesGazetteer service,Road network server,Web mapping service
based onGeographical Names,Road network featuresBase maps
OpenGIS Consortium
• Standards body for geospatial processing over the Internet– Free, public specification– Rapid specification development using
• Technology integration experimentation• Develop and spec in parallel• Testbeds
– Sponsor requirements– Industry participation
OGC Specifications
• WMS• WFS• WCS• Web Map Context• GML• SLD• Filter• Catalog
• WCTS• Grid Coverages• Location Services• Simple Features
– CORBA– SQL– OLE/COM
Web Map Service (WMS)
• Provides images of map data defined by a geographic / spatial component
• Provides point based query functionality
• Interoperable means of map compositing
Web Map Service (WMS)
• Interoperable, ‘just-in-time’ approach to map delivery
• Map compositing from multi-servers
GeoGratis – http://geogratis.gc.ca/
Web Mapping: Phase I
Toporama: http://toporama.cits.rncan.gc.ca/
Web Mapping: Phase I
•Interoperability•Common Standards•Services
•Interoperability•Common Standards•Services
Web Browser
Viewer Client
MapServer
MapServer
MapServer
MapServer
inte
rnet
Web Map Servers
Web Mapping with WMS
Web Map Service (WMS)
• Provides images of map data defined by a geographic / spatial component
• Provides point based query functionality• OGC adopted specification
– 1999: Version 1.0.0– 2001: Version 1.1.0– 2002: Version 1.1.1
• CGDI endorsed specification
Web Map Service (WMS)
• HTTP-based communication– HTTP GET or POST mechanism
• Operations• GetCapabilities• GetMap• GetFeatureInfo (optional)
– Operation keywords are case-insensitive– Operation values are case-sensitive
Web Feature Service (WFS)
• Feature level access to spatial data– Finer grained access and query
• Spatial and non-spatial query capability– Attribute and / or geometry
• Returns GML– Can further transform with XSLT to SVG, style with
SLD, etc.
• Transactional capability– INSERT, UPDATE, DELETE, LOCK, …
• Security considerations
Web Feature Service (WFS)
• GetCapabilities– Provides XML ‘Capabilities’ or service functionality
metadata, and feature metadata– Parameters
• Version (version of specification)• Service (multiple services may exist from this service, e.g.
WMS, WFS, WCS)• Request (GetCapabilities)
http://ceoware2.ccrs.nrcan.gc.ca/cubewerx/cwwfs/cubeserv.cgi?datastore=CEOWARE2&version=1.0.0&service=WFS&request=GetCapabilities
Web Feature Service (WFS)
• DescribeFeatureType– Provides schema information about a feature type
(fieldnames, data types)– Parameters
• Version (version of specification)• Service (multiple services may exist from this service, e.g.
WMS, WFS, WCS)• Request (DescribeFeatureType)• Typename (name of feature type)http://ceoware2.ccrs.nrcan.gc.ca/cubewerx/cwwfs/
cubeserv.cgi?datastore=CEOWARE2&version=1.0.0&service=WFS&request=DescribeFeatureType&typename=EOS_DATA_GATEWAYS
Web Feature Service (WFS)
• GetFeature– Provides query interface of data– Parameters
• Version (version of specification)• Service (multiple services may exist from this service, e.g.
WMS, WFS, WCS)• Request (GetFeature)• Typename (name of feature type)• Filter (more on this later)http://ceoware2.ccrs.nrcan.gc.ca/cubewerx/cwwfs/
cubeserv.cgi?datastore=CEOWARE2&version=1.0.0&service=WFS&request=GetFeature&typename=EOS_DATA_GATEWAYS
Geography Markup Language (GML)
• XML encoding of geospatial information– XML dialect
• Basic application framework for handling geospatial information
• Enables complex features & feature associations between data
• Human-readable• Can be processed by many XML tools in various
development environments
Geography Markup Language (GML)
GMLSchemas
GeometryDefinitions
ApplicationSchema
InformationCommunityDefinition
InstanceDocument
Data InstanceAs static data or
throughService Instance
Geography Markup Language (GML)
• New features in version 3.0.0– Topology– Temporal– Enhanced Geometry– Coverages– Units of Measure
Styled Layer Descriptors (SLD)
• Symbolization to map data• Styling• Addresses lack of symbolization within
current and past OGC services• Cartographic design of GeoData• Augments OpenGIS specifications
– Can custom style WMS content– Can custom style WFS content
Styled Layer Descriptors (SLD)
• Example of an SLD document:
• http://cgdi-dev.geoconnections.org/prototypes/sld/gcdb.xml
Filter Encoding
• XML Definition of data query language for online services– GML used for geometry querying semantics– Used as filter grammar for OpenGIS WFS– Stand alone specification
• Can be applied to any service as a query approach
Filter Encoding
• Example:<Filter>
<PropertyIsEqualTo><PropertyName>ORGID></PropertyName><Literal>CCRS</Literal>
</PropertyIsEqualTo></Filter>
• Used in OGC WFS– http://ceoware2.ccrs.nrcan.gc.ca/cubewerx/cwwfs/cubeserv.cgi?
datastore=CEOWARE2&version=1.0.0&service=WFS&request=GetFeature&typename=EOS_DATA_GATEWAYS&filter=<Filter><PropertyIsEqualTo><PropertyName>ORGID></PropertyName><Literal>CCRS</Literal></PropertyIsEqualTo></Filter>
OpenGIS Web Map Context Documents - Overview
• ‘bookmarkable’ XML encoding of state of a web mapping application
• Analogous to ‘project’ files in most popular GIS software packages
• Enables sharing of application scenarios, demonstrative presentations, etc.
June 9-11, 2004 • Carleton University • Ottawa • Canada
Semantic Interoperability• Ability to share meaning rather than simply
exchange data• Semantic heterogeneity:
– Same ‘symbol’/term different meaning– Different terms similar meaning
• OGC currently proposes consensus approach to dealing with semantic heterogeneity
• Moving towards the use of formal Ontologies
June 9-11, 2004 • Carleton University • Ottawa • Canada
Tools– Glossaries and data dictionaries– Thesauri and Taxonomies– Metadata, XML Schemas & Data Models (i.e.
ISO 19115, GML, UML)– Formal ontologies and inference: Description
logics (DAML+OIL) <-open standard
June 9-11, 2004 • Carleton University • Ottawa • Canada
• Interoperability Overview
• Benefits of OGC in the Organization
• Examples / Demos
• OGC / Open Source Issues
• Comments/Questions/Discussion
June 9-11, 2004 • Carleton University • Ottawa • Canada
• No reinventing the wheel
• Plug-and-Play with other standards-based systems
• Multi Vendor Interoperability
• Underlying system could change – interface remains standards-based– Less impact on end clients– Not tied to specific solutions
June 9-11, 2004 • Carleton University • Ottawa • Canada
• Interoperability Overview
• Benefits of OGC in the Organization
• Examples / Demos
• OGC / Open Source Issues
• Comments/Questions/Discussion
June 9-11, 2004 • Carleton University • Ottawa • Canada
Product URL OGC Specification(s)
UMN MapServer http://mapserver.gis.umn.edu/ WMS,WFS,Context,SLDFilter,GML
PostGIS http://postgis.refractions.net/ Simple Features for SQL
MapBuilder http://mapbuilder.sourceforge.net/ WMS,Context
deegree http://deegree.sourceforge.net/ WMS,WFS,WCS,WCASWFS-G,WTS,WCTS
GeoServer http://geoserver.sourceforge.net/ WFS-T
maplab http://www.maptools.org/maplab/index.phtml WMS
Chameleon http://www.maptools.org/chameleon/index.phtml WMS,Context,WFS
inlineWMS http://sourceforge.net/projects/inlinewms WMS
JUMP http://www.vividsolutions.com/jump/ GML
GEOS http://geos.refractions.net/ Simple Features for SQL
gml4j http://gml4j.sourceforge.net/ GML
MySQL Spatial http://www.mysql.com/ OGC Geometry Model
MapSurfer http://mapsurfer.sourceforge.net/ WMS
PyOGCLib http://pyogclib.sourceforge.net/ WMS
QuickWMS http://www.inovagis.org/quickwms/ WMS
Studio http://www.maptools.org/studio/ SLD,Context,WMS
OpenMap http://openmap.bbn.com/
GeoTools http://www.geotools.org/ GML,SLD,Grid Coverages,WCTS,Filter
June 9-11, 2004 • Carleton University • Ottawa • Canada
Demo 1: application framework based on OGC standards and Open Source.
Open Source GIS products used:
• UMN Mapserver• Chameleon and PHP/Mapscript• OGR (as a PHP module)• Deegree WCaS (Web Catalog Server)
June 9-11, 2004 • Carleton University • Ottawa • Canada
Application function: find services
Uses: • OGC Web Services Stateless Catalog Profile
0.0.6 (WCAS)• ISO19119 datamodel
June 9-11, 2004 • Carleton University • Ottawa • Canada
Application function: find layers
Uses: • OGC Web Services Stateless Catalog Profile
0.0.6 (WCAS)• ISO19115 datamodel• Layers are coupled to services in the ISO19119
datamodel, so an extra request is necessary to find the service on which the layer is available
June 9-11, 2004 • Carleton University • Ottawa • Canada
Application function: querybuilder
Flow:• Perform DescribeLayer request on SLD WMS• Perform DescribeFeatureType on associated
WFS to get list of columns• Use SLD + Filter to highlight features on map
June 9-11, 2004 • Carleton University • Ottawa • Canada
Application function: download shapefile
Flow:• Perform DescribeLayer request on SLD WMS• Perform GetFeature with BBOX Filter on
associated WFS using AOI defined in application• Use OGR to convert GML to shapefile
June 9-11, 2004 • Carleton University • Ottawa • Canada
• Interoperability Overview
• Benefits of OGC in the Organization
• Examples / Demos
• OGC / Open Source Issues
• Comments/Questions/Discussion
June 9-11, 2004 • Carleton University • Ottawa • Canada
OGC / Open Source Issues
• General– “OGC Compliant” – be careful!– Namespaces in OGC XML-based documents
June 9-11, 2004 • Carleton University • Ottawa • Canada
OGC / Open Source Issues
• General– XML (GML) is very expressive yet very
verbose -> performance problems– Researchers working on ‘feature streaming’ to
deal with this issue (not yet in OGC process)– Applicability of specs in functional
applications: bridging the gap– slow emergence of specs
June 9-11, 2004 • Carleton University • Ottawa • Canada
OGC / Open Source Issues
• Semantic– Current consensus approach may limit use
outside of simple domains (i.e. where concensus cannot be achieved)
– OGC is not the only standard -> ISO, FGDC, Domain specific, W3C -> requires a ‘reference ontology’ to mediate between standards
June 9-11, 2004 • Carleton University • Ottawa • Canada
Comments/Questions/Discussion
Thanks!
Tom Kralidis (tom.kralidis at ec.gc.ca)
Jeff McKenna (mckenna at dmsolutions.ca)
Peter Pulsifer (pulsifer at magma.ca)
Bart van den Eijnden (bart at geodan.nl)
June 9-11, 2004 • Carleton University • Ottawa • Canada