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
June 9-11, 2004 • Carleton University • Ottawa • Canada
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
For Example…
Applications
Users
e.g., Transportation Planning,
Climate Change Monitoring,
Site Assessment
Services
Other
Applications
e.g., Metadata Service,
gazetteer service,
Web Map Service
Data
e.g., topographic,
thematic, imagery,
toponymy, metadata
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
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
Web Mapping: Phase I
GeoGratis – http://geogratis.gc.ca/
Toporama: http://toporama.cits.rncan.gc.ca/
Web Mapping: Phase I
•Interoperability
•Common Standards
•Services
Web Mapping with WMS
Map
Server
Viewer Client
Web Browser
Web Map Servers
internet
Map
Server
Map
Server
Map
Server
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/cubeser
v.cgi?datastore=CEOWARE2&version=1.0.0&service=WF
S&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/cubeser
v.cgi?datastore=CEOWARE2&version=1.0.0&service=WF
S&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/cubeser
v.cgi?datastore=CEOWARE2&version=1.0.0&service=WF
S&request=GetFeature&typename=EOS_DATA_GATEWA
YS
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)
Data Instance
Instance
Document
Information
Community
Definition
Application
Schema
Geometry
Definitions
GML
Schemas
As static data or
through
Service Instance
Geography Markup Language
(GML)
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)
Styled Layer Descriptors (SLD)
• Example of an SLD document:
• http://cgdidev.geoconnections.org/prototypes/sld/gcd
b.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?datastor
e=CEOWARE2&version=1.0.0&service=WFS&request=GetFeature&typ
ename=EOS_DATA_GATEWAYS&filter=<Filter><PropertyIsEqualTo><
PropertyName>ORGID></PropertyName><Literal>CCRS</Literal></Pr
opertyIsEqualTo></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.
Web Mapping – Same data;
multiple applications (OpenGIS
Web Map Context Documents)
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,SLD
Filter,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,WCAS
WFS-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
June
9-11, 2004 • Carleton
University • Ottawa • Canada
OpenMap
http://openmap.bbn.com/
GeoTools
http://www.geotools.org/
GML,SLD,Grid Coverages,WCTS,Filter
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
• Demo 2 (Jeff McKenna)
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
June
9-11, 2004 • Carleton University • Ottawa • Canada
Descargar

OGC in Open Source Products