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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

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June 9-11, 2004 • Carleton University • Ottawa • Canada

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  1. 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

  2. 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

  3. 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

  4. Infrastructure • Many pieces working independent of make, model • Open interface • Can communicate with other things • Transparent / Invisible • Cooperative • Distributed

  5. 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

  6. Web Services • Independent of • operating systems • programming languages • Organizations • How? • non-proprietary data / messaging standards • eXtensible Markup Language (XML)

  7. 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

  8. Web Services- Benefits • Lower software integration costs • Maintaining legacy systems • Using standards lowers IT costs of collaboration with external partners, vendors, clients

  9. Applications e.g., Transportation Planning, Climate Change Monitoring, Site Assessment Users Services e.g., Metadata Service, gazetteer service, Web Map Service Other Applications Data e.g., topographic, thematic, imagery, toponymy, metadata Web Services Architecture Approach For Example… A trip planning web site that calculates the best route between two cities uses Gazetteer service, Road network server, Web mapping service based on Geographical Names, Road network features Base maps

  10. 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

  11. WMS WFS WCS Web Map Context GML SLD Filter Catalog OGC Specifications • WCTS • Grid Coverages • Location Services • Simple Features • CORBA • SQL • OLE/COM

  12. 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

  13. Web Map Service (WMS) • Interoperable, ‘just-in-time’ approach to map delivery • Map compositing from multi-servers

  14. Web Mapping: Phase I • GeoGratis – http://geogratis.gc.ca/ • Toporama: http://toporama.cits.rncan.gc.ca/

  15. Interoperability • Common Standards • Services Web Mapping: Phase I • Interoperability • Common Standards • Services

  16. MapServer MapServer MapServer MapServer Web Browser Web Map Servers Viewer Client internet Web Mapping with WMS

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. Instance Document Data Instance Information Community Definition Application Schema GML Schemas Geometry Definitions Geography Markup Language (GML) As static data or through Service Instance

  25. Geography Markup Language (GML)

  26. Geography Markup Language (GML) • New features in version 3.0.0 • Topology • Temporal • Enhanced Geometry • Coverages • Units of Measure

  27. 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

  28. Styled Layer Descriptors (SLD)

  29. Styled Layer Descriptors (SLD) • Example of an SLD document: • http://cgdi-dev.geoconnections.org/prototypes/sld/gcdb.xml

  30. 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

  31. 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>

  32. 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.

  33. Web Mapping – Same data; multiple applications (OpenGIS Web Map Context Documents)

  34. 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

  35. 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

  36. 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

  37. 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

  38. 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

  39. June 9-11, 2004 • Carleton University • Ottawa • Canada

  40. 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

  41. 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

  42. 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

  43. 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

  44. 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

  45. Demo 2 (Jeff McKenna) June 9-11, 2004 • Carleton University • Ottawa • Canada

  46. 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

  47. OGC / Open Source Issues • General • “OGC Compliant” – be careful! • Namespaces in OGC XML-based documents June 9-11, 2004 • Carleton University • Ottawa • Canada

  48. 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

  49. 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

  50. 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 June 9-11, 2004 • Carleton University • Ottawa • Canada

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