1. OGC Web Services : an introduction
Ollie Raymond
IUGS Commission for the Management and Application of Geoscience Information (CGI)

2. Overview An Introduction to OGC and CGI
Why do we need data transfer standards?
Types of OGC web services
Standards for symbolising and querying OGC web services
Science community data standards

3. Open Geospatial Consortium (OGC)
an international industry consortium of over 527 companies, government agencies and universities
a consensus process to develop publicly available interface standards
OGC Standards support interoperable solutions that spatially enable the Web, wireless and location-based services and mainstream IT
empower technology developers to make complex spatial information and services accessible and useful with all kinds of applications.

4. Open Geospatial Consortium (OGC)
OGC standards include:
Protocols for delivering vector and raster spatial data
eg, Web Map Service (WMS), Web Feature Service (WFS), Web Coverage Service (WCS)
Markup languages for generic spatial data
e.g., Geography Markup Language (GML), KML
Specific science domain markup languages
e.g., Observations & Measurements (O&M), WaterML, GroundWaterML, CityGML, GeoSciML

5. Commission for the Management and Application of Geoscience Information (CGI)
A commission of the International Union of Geological Sciences
CGI's mission is to foster the interoperability and exchange of geoscience information by:
active community leadership, collaboration, education, and
the development and promotion of geoscience information standards and best practice
works closely with OGC

6. Commission for the Management and Application of Geoscience Information (CGI)
CGI Council
global regional representatives
Working groups
GeoSciML Standards Working Group (with OGC)
EarthResourceML Working Group
Geoscience Terminology Working Group
Geoscience Information in Africa (GIRAF)
3D Geoscience Data (informal group)

7. Interoperability Simply put… “My stuff works with your stuff”
Sharing data in a way that many people can access data via the same methods, in the same format, with the same standard terminology from many different data sources
The Holy Grail of shared data providers

8. Why do we need data transfer standards?
ease and certainty of communication across borders
ability to easily combine standardised data from different sources
ability to repeat analyses on multiple datasets from different sources
productivity, repeatability, time saving for users and developers

9. File downloads in different formats
Client applications
(web portals, desktop GIS, mobile devices, etc)
CSV
SHP
GDB
File downloads in different formats
lithology = ‘granite’
age = ‘Archean’
rock_type = ‘Granite’
unit_age = ‘Archaean’
Different data structures
and terminology
LITH = ‘GRNT’
AGE = ‘ARCHEAN’
Database
Database
Database
Spatial data stores
(e.g., Oracle, PostGres, ArcGIS, Mapinfo)

10. ESRI MAPINFO An example from an Australian state border… Western
Northern
Territory
Label
Age
Description
ESRI MAPINFO

11. Client applications CSV SHP GDB lithology = ‘granite’ age = ‘Archean’
(web portals, desktop GIS, mobile devices, etc)
CSV
SHP
GDB
lithology = ‘granite’
age = ‘Archean’
rock_type = ‘Granite’
unit_age = ‘Archaean’
LITH = ‘GRNT’
AGE = ‘ARCHEAN’
Database
Database
Database
Spatial data stores
(e.g., Oracle, PostGres, ArcGIS, Mapinfo)

12. Client applications single format lithology = ‘granite’
(web portals, desktop GIS, mobile devices, etc)
single format
lithology = ‘granite’
age = ‘Archean’
Database
Database
Database
Spatial data stores
(e.g., Oracle, PostGres, ArcGIS, Mapinfo)

13. Standards-based web services
Client applications
(web portals, desktop GIS, mobile devices, etc)
single format
lithology = ‘granite’
age = ‘Archean’
Standards-based web services
Database
Database
Database
Spatial data stores
(e.g., Oracle, PostGres, ArcGIS, Mapinfo)

14. Client applications Spatial data stores
(web portals, desktop GIS, mobile devices, etc)
e.g., WMS, WFS
OGC Web Service Standard
mapping
e.g., GeoSciML, ERML, O&M
Scientific Community Data Transfer Standard
e.g.,
Community-Agreed Standard Vocabularies
Database
Database
Database
Spatial data stores
(e.g., Oracle, PostGres, ArcGIS, Mapinfo)

15. and others… Client applications Spatial data stores
(web portals, desktop GIS, mobile devices, etc)
and others…
Web Server application
Web Server application
Web Server application
OGC Web Service Standard
Scientific Community Data Transfer Standard
Community-Agreed Standard Vocabularies
mapping
mapping
mapping
Database
Database
Database
Spatial data stores
(e.g., Oracle, PostGres, ArcGIS, Mapinfo)

16. Client applications Spatial data stores
(web portals, desktop GIS, mobile devices, etc)
e.g., GeoSciML WFS
Standard web service
Web Server application
Web Server application
Web Server application
e.g., GeoServer, ArcGIS Server, Deegree, GeoNetwork
OGC Web Service Standard
e.g., WMS, WFS
Scientific Community Data Transfer Standard
e.g., GeoSciML, ERML, O&M
Community-Agreed Standard Vocabularies
e.g.,
mapping
mapping
mapping
Database
Database
Database
Spatial data stores
(e.g., Oracle, PostgreSQL, ArcGIS, MapInfo)

17. OGC Web Services Standards
Web Map Service - WMS
a WMS delivers an image (or map) of your data to the internet
eg, PNG, JPG

18. OGC Web Services Standards
Web Map Service - WMS
a WMS delivers an image (or map) of your data to the internet
eg, PNG, JPG
a WMS may contain many data types, or “feature layers”

19. OGC Web Services Standards
Web Map Service - WMS
a WMS image may be queried at a point to return attribute data about features at that location
click!

20. OGC Web Services Standards
Web Map Service - WMS
a WMS image may be queried at a point to return attribute data about features at that location
data for only one or a few features can be accessed at a time

21. OGC Web Services Standards
Web Map Service - WMS
WMS data layers may be styled to produce different images of the data

22. OGC Web Services Standards
Web Map Service - WMS
a WMS is identified by a URL “endpoint”
eg,
the endpoint URL on its own will not resolve in a normal web browser
an endpoint URL is a stub to which further standard parameters are added to create a WMS “request”

23. OGC Web Services Standards
Web Map Service - WMS
standard WMS request parameters
added on to endpoint to make very long URLs
GetCapabilities
request=GetCapabilities&
service=WMS&
version=1.3.0
A GetCapabilities document is XML-formatted metadata about the web service
service name, owner details, spatial extents
abstract, keywords
layer names and descriptions
supported spatial reference systems (projections) and image formats
layer symbolisation and legends

24. OGC Web Services Standards
Web Map Service - WMS
standard WMS request parameters
GetMap – returns a map image to the client
request=GetMap&
service=WMS&
version=1.3.0&
bbox=-50,110,-5,155&
crs=EPSG:4326&
width=700&height=700&
format=image/png&
layers=AUS_GA_2500k_MiscLines&
styles=….

25. OGC Web Services Standards
Web Map Service - WMS
standard WMS request parameters
GetFeatureInfo – returns attribute information about features at a location
request=GetFeatureInfo&
service=WMS&
version=1.3.0&
layers=Scanned_250K_Geological_Map_Index&
query_layers=Scanned_250K_Geological_Map_Index&
info_format=text/html&
bbox= , , , &
crs=EPSG:3857&
i=400&j=400&width=800&height=800

26. OGC Web Services Standards
Web Map Service - WMS
standard WMS request parameters
Styled Layer Descriptor (SLD)
used as additional parameters in a GetMap request
parameters to describe colours, line styles, markers, and patterns for vector data
parameters to describe colour ramps and categories for raster data

27. OGC Web Services Standards
Web Map Service - WMS
standard WMS request parameters
Styled Layer Descriptor (SLD)

28. OGC Web Services Standards
Web Map Service - WMS
standard WMS request parameters
Styled Layer Descriptor (SLD)
can incorporate a query filter into an SLD to symbolise features based on property values
symbolisation can be delivered by the service provider as part of the web service
multiple styles can be supplied for one WMS layer
the styles are advertised in the WMS GetCapabilities document
or symbolisation can be applied to a web service via an SLD sent from the client application

29. OGC Web Services Standards
Web Feature Service - WFS
XML-based markup text streamed to the internet
contains the real data, not a picture of it
no symbolisation is contained within a WFS
a client application is required to do the symbolisation (e.g., QGIS, ArcMap)

30. OGC Web Services Standards
Web Feature Service - WFS
Simple Features WFS
a flat list of properties (attributes)
ie, a spreadsheet or shapefile
simple XML property Xpaths
no hierarchical or nested structure
no multiple property values
spatial features formatted using GML
a single spatial geometry type
XML structure is typically not controlled by a community schema
Complex Features WFS
properties may be hierarchical, nested, with complex relations between features
ie, a relational database
properties may contain multiple values
may contain more than one geometry type
XML structure is typically controlled by a community schema
eg, GeoSciML, EarthResourceML

31. OGC Web Services Standards
Web Feature Service - WFS
Simple Features
GeologicUnit
lithology = ‘granite’
Complex Features
gsmlb:GeologicUnit
gsmlb:composition [1]
gsmlb:CompositionPart
gsmlb:material
gsmlb:RockMaterial = ‘granite’
gsmlb:composition [2]
gsmlb:RockMaterial = ‘tonalite’

32. OGC Web Services Standards
Web Feature Service - WFS
standard WFS request parameters
GetCapabilties
same function as for WMS
GetFeature
request=GetFeature&
service=WFS&
VERSION=1.1.0&
maxfeatures=10&
typeName=gsml:Borehole&
outputFormat=gml3

33. OGC Web Services Standards
Filter Encoding Standard - FES
an standard syntax to construct query expressions on web services
defines a standard set of query operators. e.g.,
Spatial Operators
BBOX
Intersects
Overlaps
Within
etc…
Comparison Operators
PropertyIsEqualTo
PropertyIsLessThan
PropertyIsGreaterThan
PropertyIsLike
And/Or
etc…
other functions…
ResourceId
SortProperty
etc…

34. <wfs:GetFeature> <wfs:Query typeNames="Person"> <wfs:PropertyName>lastName</wfs:PropertyName> <fes:Filter> <fes:And> <fes:And> <fes:PropertyIsGreaterThanOrEqualTo> <fes:ValueReference>Person/mailAddress/Address/streetNumber</fes:ValueReference> <fes:Literal>1</fes:Literal> </fes:PropertyIsGreaterThanOrEqualTo> <fes:PropertyIsLessThanOrEqualTo> <fes:ValueReference>Person/mailAddress/Address/streetNumber</fes:ValueReference> <fes:Literal>100</fes:Literal> </fes:PropertyIsLessThanOrEqualTo> </fes:And> <fes:And> <fes:PropertyIsEqualTo> <fes:ValueReference>Person/mailAddress/Address/streetName</fes:ValueReference> <fes:Literal>Main Street</fes:Literal> </fes:PropertyIsEqualTo> <fes:PropertyIsEqualTo> <fes:ValueReference>Person/mailAddress/Address/city</fes:ValueReference> <fes:Literal>Canberra</fes:Literal> </fes:PropertyIsEqualTo> </fes:And> </fes:And> </fes:Filter> </wfs:Query> </wfs:GetFeature>
QUERY: Find the last name of people who live between 1 and 100 Main Street, Canberra

35. OGC Web Services Standards
Catalog Service for the Web - WFS
used to publish and search collections of descriptive information (metadata) for datasets, services, and related information objects
similar to WFS, CSW publishes XML-encoded information
CSW records describe datasets, not individual features
ISO Metadata standard is commonly used for spatial datasets
some overlap with WFS and WMS GetCapabilities
URL endpoint, and standard request parameters
GetCapabilities
GetRecords
DescribeRecord
Harvest
etc…

36. Application Schemas
A science community may define a standard schema to govern the structure of shared data (ie, an application schema)
GeoSciML, EarthResourceML, WaterML, CityGML, etc
Step 1 – a data model, typically presented using UML
define features with descriptive properties and relationships
optional/mandatory properties, single/multiple relationships

37. Application Schemas
Step 2 – encode the data model as an XML Application Schema markup language (.xsd)
e.g.,
Step 3 – use the schema to validate WFS services to ensure that they conform to the structure dictated by the data model
Optional Step 4 – further Schematron (.sch) rules may be written to enforce extra constraints that are not specified by an Application Schema, for example:
define a “profile” of an App Schema (e.g. INSPIRE profile of GeoSciML)
extra business rules for a specific user community. e.g.,make an optional property mandatory, or
enforce the use of particular vocabularies to control data content

38. OGC, ISO, and CGI Application Schemas
Geography Markup Language (GML – OGC & ISO 19136)
for encoding spatial features; 1D, 2D, 3D shapes
Observations & Measurements (O&M – OGC & ISO 19156)
sampling features, and observations made on features
Metadata (ISO 19115)
for encoding metadata about geographic data and services
e.g., dataset identification, spatial and temporal information, data quality, and distribution methods of digital geographic data

39. OGC, ISO, and CGI Application Schemas
Geoscience Markup Language (GeoSciML – CGI & OGC “in press”)
geological features, geological time, and extends O&M for geological purposes
Earth Resource Markup Language (EarthResourceML – CGI)
for mineral occurrences, mines, and related activities
Groundwater Markup Language (GWML – OGC)
extends GeoSciML and O&M to describe hydrogeological features and processes
Full list of OGC application schema standards

40. Refreshment break
10: :30 am