OGC Web Services an introduction Ollie Raymond IUGS

OGC Web Services : an introduction Ollie Raymond IUGS Commission for the Management and Application of Geoscience Information (CGI) www. cgi-iugs. org

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

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. • http: //www. opengeospatial. org/

Open Geospatial Consortium (OGC) OGC standards include: • Protocols for delivering vector and raster spatial data o eg, Web Map Service (WMS), Web Feature Service (WFS), Web Coverage Service (WCS) • Markup languages for generic spatial data o e. g. , Geography Markup Language (GML), KML • Specific science domain markup languages o e. g. , Observations & Measurements (O&M), Water. ML, Ground. Water. ML, City. GML, Geo. Sci. ML

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 • http: //www. cgi-iugs. org/

Commission for the Management and Application of Geoscience Information (CGI) • CGI Council o global regional representatives • Working groups o Geo. Sci. ML Standards Working Group (with OGC) o Earth. Resource. ML Working Group o Geoscience Terminology Working Group o Geoscience Information in Africa (GIRAF) o 3 D Geoscience Data (informal group)

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

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

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

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

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

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

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

Client applications (web portals, desktop GIS, mobile devices, etc) OGC Web Service Standard e. g. , WMS, WFS Scientific Community Data Transfer Standard e. g. , Geo. Sci. ML, ERML, O&M Community-Agreed Standard Vocabularies mapping e. g. , http: //resource. geosciml. org mapping Spatial data stores Database (e. g. , Oracle, Post. Gres, Arc. GIS, Mapinfo)

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

Client applications (web portals, desktop GIS, mobile devices, etc) e. g. , Geo. Sci. ML WFS Standard web service Web Server application e. g. , Geo. Server, Arc. GIS Server, Deegree, Geo. Network OGC Web Service Standard e. g. , WMS, WFS Scientific Community Data Transfer Standard e. g. , Geo. Sci. ML, ERML, O&M Community-Agreed Standard Vocabularies e. g. , http: //resource. geosciml. org mapping Spatial data stores Database (e. g. , Oracle, Postgre. SQL, Arc. GIS, Map. Info)

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

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”

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 k ! c cli

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

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

OGC Web Services Standards Web Map Service - WMS • a WMS is identified by a URL “endpoint” • eg, http: //services. ga. gov. au/site_9/services/Geophysical_Grids/Map. Server/WMSServer • 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”

OGC Web Services Standards Web Map Service - WMS • standard WMS request parameters • added on to endpoint to make very long URLs • Get. Capabilities • http: //services. ga. gov. au/site_9/services/Geophysical_Grids/Map. Server/WMSServer? • request=Get. Capabilities& • service=WMS& • version=1. 3. 0 • A Get. Capabilities 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

OGC Web Services Standards Web Map Service - WMS • standard WMS request parameters • Get. Map – returns a map image to the client • http: //www. ga. gov. au/gis/services/earth_science/GA_Surface_Geology_of_Australia/Map. Serv er/WMSServer? • request=Get. Map& • service=WMS& • version=1. 3. 0& • bbox=-50, 110, -5, 155& • crs=EPSG: 4326& • width=700&height=700& • format=image/png& • layers=AUS_GA_2500 k_Misc. Lines& • styles=….

OGC Web Services Standards Web Map Service - WMS • standard WMS request parameters • Get. Feature. Info – returns attribute information about features at a location • http: //services. ga. gov. au/site_9/services/Scanned_250 k_Geological_Map_Index/Map. Server/ WMSServer? • request=Get. Feature. Info& • service=WMS& • version=1. 3. 0& • layers=Scanned_250 K_Geological_Map_Index& • query_layers=Scanned_250 K_Geological_Map_Index& • info_format=text/html& • bbox=16196985. 9104, -4439106. 78725, 16419624. 892, -4163881. 144& • crs=EPSG: 3857& • i=400&j=400&width=800&height=800

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

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

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 Get. Capabilities document • or symbolisation can be applied to a web service via an SLD sent from the client application

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, Arc. Map)

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 • Complex Features WFS • properties may be hierarchical, nested, with complex relations between features • ie, a relational database • properties may contain multiple values • no multiple property values • may contain more than one geometry type • spatial features formatted using GML • a single spatial geometry type • XML structure is typically controlled by a community schema • XML structure is typically not controlled by a community schema • eg, Geo. Sci. ML, Earth. Resource. ML

OGC Web Services Standards Web Feature Service - WFS • Simple Features • Complex Features Geologic. Unit lithology = ‘granite’ gsmlb: Geologic. Unit gsmlb: composition [1] gsmlb: Composition. Part gsmlb: material gsmlb: Rock. Material = ‘granite’ gsmlb: composition [2] gsmlb: Composition. Part gsmlb: material gsmlb: Rock. Material = ‘tonalite’

OGC Web Services Standards Web Feature Service - WFS • standard WFS request parameters • Get. Capabilties • • same function as for WMS Get. Feature • • http: //geossdi. dmp. wa. gov. au/services/wfs? request=Get. Feature& service=WFS& VERSION=1. 1. 0& maxfeatures=10& type. Name=gsml: Borehole& output. Format=gml 3

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 • Property. Is. Equal. To • Property. Is. Less. Than • Property. Is. Greater. Than • Property. Is. Like • And/Or • etc… • other functions… • Resource. Id • Sort. Property • etc…

<wfs: Get. Feature> <wfs: Query type. Names="Person"> QUERY: Find the last name of <wfs: Property. Name>last. Name</wfs: Property. Name> people who live between 1 and <fes: Filter> <fes: And> 100 Main Street, Canberra <fes: And> <fes: Property. Is. Greater. Than. Or. Equal. To> <fes: Value. Reference>Person/mail. Address/street. Number</fes: Value. Reference> <fes: Literal>1</fes: Literal> </fes: Property. Is. Greater. Than. Or. Equal. To> <fes: Property. Is. Less. Than. Or. Equal. To> <fes: Value. Reference>Person/mail. Address/street. Number</fes: Value. Reference> <fes: Literal>100</fes: Literal> </fes: Property. Is. Less. Than. Or. Equal. To> </fes: And> <fes: Property. Is. Equal. To> <fes: Value. Reference>Person/mail. Address/street. Name</fes: Value. Reference> <fes: Literal>Main Street</fes: Literal> </fes: Property. Is. Equal. To> <fes: Value. Reference>Person/mail. Address/city</fes: Value. Reference> <fes: Literal>Canberra</fes: Literal> </fes: Property. Is. Equal. To> </fes: And> </fes: Filter> </wfs: Query> </wfs: Get. Feature>

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 19115 Metadata standard is commonly used for spatial datasets some overlap with WFS and WMS Get. Capabilities • URL endpoint, and standard request parameters • • • Get. Capabilities Get. Records Describe. Record Harvest etc…

Application Schemas • A science community may define a standard schema to govern the structure of shared data (ie, an application schema) • Geo. Sci. ML, Earth. Resource. ML, Water. ML, City. GML, etc Step 1 – a data model, typically presented using UML • define features with descriptive properties and relationships • optional/mandatory properties, single/multiple relationships

Application Schemas Step 2 – encode the data model as an XML Application Schema markup language (. xsd) • e. g. , http: //schemas. geosciml. org/geosciml/4. 0/geo. Sci. MLBasic. xsd 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 Geo. Sci. ML) • 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

OGC, ISO, and CGI Application Schemas Geography Markup Language (GML – OGC & ISO 19136) • for encoding spatial features; 1 D, 2 D, 3 D 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

OGC, ISO, and CGI Application Schemas Geoscience Markup Language (Geo. Sci. ML – CGI & OGC “in press”) • geological features, geological time, and extends O&M for geological purposes Earth Resource Markup Language (Earth. Resource. ML – CGI) • for mineral occurrences, mines, and related activities Groundwater Markup Language (GWML – OGC) • extends Geo. Sci. ML and O&M to describe hydrogeological features and processes Full list of OGC application schema standards http: //www. opengeospatial. org/docs/is

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