OGC in Open Source Products

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 gt data gt
  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
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
OGC Specifications

• WMS
• WFS
• WCS
• Web Map Context
• GML
• SLD
• Filter
• Catalog

• 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
Web Mapping Phase I

• Interoperability
• Common Standards
• Services

16
Web Mapping with WMS
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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

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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/cu
  beserv.cgi?datastoreCEOWARE2version1.0.0servic
  eWFSrequestGetCapabilities

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/cu
  beserv.cgi?datastoreCEOWARE2version1.0.0servic
  eWFSrequestDescribeFeatureTypetypenameEOS_DAT
  A_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/cu
  beserv.cgi?datastoreCEOWARE2version1.0.0servic
  eWFSrequestGetFeaturetypenameEOS_DATA_GATEWAY
  S

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
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)
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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
• ltFiltergt
• ltPropertyIsEqualTogt
• ltPropertyNamegtORGIDgtlt/PropertyNamegt
• ltLiteralgtCCRSlt/Literalgt
• lt/PropertyIsEqualTogt
• lt/Filtergt
• Used in OGC WFS
• http//ceoware2.ccrs.nrcan.gc.ca/cubewerx/cwwfs/cu
  beserv.cgi?datastoreCEOWARE2version1.0.0servic
  eWFSrequestGetFeaturetypenameEOS_DATA_GATEWAY
  SfilterltFiltergtltPropertyIsEqualTogtltPropertyNamegt
  ORGIDgtlt/PropertyNamegtltLiteralgtCCRSlt/Literalgtlt/Prop
  ertyIsEqualTogtlt/Filtergt

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.

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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 (DAMLOIL) lt-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 -gt
  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 -gt ISO, FGDC, Domain
  specific, W3C -gt 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