Spatial Data Infrastructure involves data modeling, metadata, and web services for data access. Data modeling involves conceptualizing user needs, developing a data model, encoding the data, and publishing it. Metadata provides information about spatial data to improve discovery. Registry and discovery services allow querying metadata. Web services like WMS and WFS enable accessing and manipulating mapped features through standard interfaces.

1. Spatial Data Infrastructure
Data modelling and web services for data access
Jean-Christophe Desconnets
desconne@mpl.ird.fr

2. Outline
• Introduction
• Data Modelling
– Methodology
• Conceptualization
• Data Modelling
• Data Encoding
• Data Publication
• Metadata
– Concepts and role
– Metadata profile
• Registry and discovery service
• Web services for data access

3. Introduction
Organizational
components
Functional
components
Technical
components
Governance and monitoring
Users
Producers
Strategy/Objectives
Scope
Contents (spatial data)
SDI features
Implementation
Data
Services
Applications
Technical infrastructure

4. Data Modelling

5. Issues & purposes of data modelling
Main Issues
• SDI implies data exchanges. These data fulfill a need.
• Crucial to understand the need to define how to model the real world
features of interest
• To build interoperable SDI
– Technical interoperability
– Semantic interoperability (object vocabulary)
Data modelling purposes
To define a consensual data model (feature types & its properties, relations),
extendable based on user-needs and existing data

6. The differents steps for data modelling
The four main steps
• Step 1: Conceptualization of user-needs
– Capture use cases and user-needs
• Step 2: Data modelization
– From user-needs to feature types specification
• Step 3: Data Encoding
– From the data model to data format exchange
• Step 4: Data Publishing
– Originated Data vs. Harmonised Data

7. • Goal
– Identify the feature of interest for the SDI to
fullfill the user-needs
• Materials
– Based on survey of existing databases and
Standards to analyse and formalise
• Outcomes
– User-needs expressed by use cases (UML
formalism)
Conceptualization step
ISO 19101
Concept of features
& their properties
ISO 19109
The general features
model
Conceptualization
Analysis/Business model
Domain
understanding
& use cases

8. Conceptualization step
• Example with the use cases expressed for Protected Areas dataset in
INSPIRE Framework
Source: INSPIRE Data Specification on Protected Sites - Guidelines v3.0
Use case definition
‘A use case is initiated by a user with a particular goal in
mind, and completes successfully when that goal is
achieved. It describes the sequence of interactions between
actors and the system necessary to deliver the service that
satisfies the goal.’

9. Conceptualization step
• Example with the use cases expressed for Protected Areas dataset in
INSPIRE Framework
Source: INSPIRE Data Specification on Protected Sites - Guidelines v3.0
Narrative description

10. Data modelling
• Goal
– Define an application
schema based on user-needs
• Materials
– UML formalism to describe
formally the structure of
features & ISO, OGC
specifications (shared
concepts)
• Outcomes
– Guidelines of an application
schema
model
Conceptualization
UML meta model
concepts in conceptual
schema language
Guidelines to express
features and
application schema
Modelling
UML (ISO 19109)
Feature
type
definition
Appl.
schema
ISO 19000
standards
schema
Integrated inused in

11. Data modelling
Application schema definition
Describes, in a standard way, what information the service
will provide to the world.
It consists of a set of feature types with relationships
between them. Each feature type is defined using a set of
data types.
Application
schema
Data type
*
Feature type
*

12. Data modelling
• Example with the use cases expressed for Protected Areas dataset in
INSPIRE Framework:
Source: INSPIRE Data Specification on Protected Sites - Guidelines v3.0
• 3 application schemas proposed:
• Simple
• Full
• Natura2000 (European directive on Nature Conservation)

13. Data encoding
• Goal
– Convert the UML model to a
GML application schema
• Materials
• ISO 19136:2007 Geographic
information -- Geography Markup
Language (GML)
• Outcomes
– A GML application schema
Convert
Modelling
Concept of XML
schema as a schema
language (W3C)
How to express features
type and appl. schema
in GML
Encoding
GML (ISO 19136)
GML
feature
types
GML
appl.
schema
ISO, GML
& domain
types
librairies
Integrated inused in

14. Data encoding
GML: Geographic Markup Language
Defines an encoding of every required ISO standard by
providing an XML schema and defines mapping rules for
each feature types and data types of the general feature
models
• Example of a conversion of ProtectedArea UML Class to GML application
schema (NatureGIS project)

15. Data Publishing
• Goal
– Setting up on-line services to serve
harmonised data
• Materials
– OGC web services specifications
• Outcomes
– Implementation of a CSW/WFS
which serves metadata of data and
data (GML application schema) on
demand
Encoding
publish
Webservices handling
access, security, queries
and serves GML
Publish/Exchange
OGC WebServices
data
internet
Query exchange

16. Internal data model vs exposed feature types
• Exposed data features are the result of a ‘mapping’ of internal
data model to GML application model
– To expose only a subset or a view of internal data
• ‘Mapping’ called ‘data remodelling’ prodiving by ETL tool
• Remodelling data can be stored inside:
– File
– Database
– Or created on the fly

17. Internal data model vs exposed feature types
• Schema of simple ‘mapping’ on protectedArea FeatureType
Data store
CODE
N2000
NAME
Table NaturePark
NAME
EMAIL
Table CONTACT
WFS
Service
fid
siteName
Contact
Name
Email
Natura2000
FeatureType: ProtectedArea
<Mapping>

18. Metadata

19. What is metadata ?
‘Data about data’
Basically, structured information & description which make information
understandable & shareable for users over time
Provide
Description of characteristics of a set of data, such as the content, quality,
currency, access and availability,…
Used
By search engines to improve the matching between user queries and
description resources
For geographical dataset
Provide spatial components such as coordinate reference system, spatial
representation, spatial localisation

20. Why metadata ?
A key to true usability and interoperability in the GIS environnment
• For data provider
– Reduce the cost of losing information about spatial dataset
– Increase the usability and value of all datasets over time
– Protect GIS data investments in organisations by providing information about their
data holdings
• Arises from the increasing recognition of the benefits it provides as the use and
amounts of data increases

21. Metadata Standards
ISO 19115:2003 Geographic
Information - Metadata
ISO 19119:2005 -
Geographic Information -
Services

22. ISO/TS 19139:2007 - Geographic information - Metadata XML Schema Implementation
XML encoding of ISO 19115/119 and comprehensive implementation
specification for digital geographic datasets
Metadata Standards
ISO 19115-2:2005 -
Geographic Information -
Imagery

23. Metadata profiles
A subset of ISO Standard and extended elements, if necessary, based on
requirements of a user community
ISO Core
elements
standard
profile
Extended
elements

24. Illustration
• Illustration of WMS service capabilities, service metadata and data
metadata
OGC Services

25. Metadata tools
• Web text Editor to produce XML
• Harvest tool to retrieve metadata through Web service
capabilities or Web service CatalogGoal: produce a compliant XML ISO 19139 metadata recordsMetadata editor
Harvester

26. Registry and
Discovery service

27. Concept of Registry
Registry Web Service
– Interfaces for querying & managing a metadata repository
• Registry client
– Application used to query the registry and submit items to be registered
• Catalog
– Based on an information model at a high level of abstraction to
define type of objects stored in the registry and how they are
organised (ebRIM, UDDI)
‘The role of registry is to extract and index a subset of the information held
on metadata in a way that the records can be easily be found again on the
basis of specific criteria’

28. Concept of Registry
Data
Service
Interface
request response
Data content
& service
Service
metadata
Data
metadata
ISO 19119
ISO 19115
Metadata
Catalog
Registry
Registry
Interface
request response
Service
metadata
Data
metadata
publish

29. Discovery web service
• Based on OGC Catalog specifications
Describes several ‘binding protocols’
– Web profile (CS-W), CORBA, ….
• Purpose of CS-W
Describes the operations to request & answer messages that are common to
all web-based catalog services of spatial datasets
• Several application profiles
– AP ISO 19115: Catalog Service for the Web
– AP EbRIM: Web Registry Service
The gateway for access to service and data

30. Discovery service capabilities & example
CSW(T) Operation Description
GetCapabilities Common OGC mechanism by which the service is
described itself by metadata
GetRecords Principal query operation of the interface
allowing to obtain one or more item s from the
catalogue
GetRecordById Simple way toretrieve a record from a catalog by
its identifier
Harvest Operation to harvest item from one catalog to
another
Transaction Operation used to i nsert, update or delete an
item from a catalog
Main operations of CS-W

31. Discovery service capabilities & example
GetCapabilities
http://demo20…/WS/csw?REQUEST=GetCapabilities&SERVICE=CSW&VERSION=2.0.2
request
response

32. Multi-lingual discovery
Construct queries and retrieve results which may bear on multi-
lingual catalogs (metadata)
– On the catalog contents: internationalisation
• Encoding mechanism XML 19139 (code list, embedded translation,
etc.)
• Use of controlled vocabularies: Thesauri
– On discovery applications: construction and propagation
of multi-lingual requests
– Use of the URI of terminological concepts
– Service to access the vocabulary (Thesaurus web service)

33. Multi-lingual discovery
Requirements to build a multi-lingual request:
• Extended capabilities of CSW

34. Multi-lingual discovery
Requirements to build a multi-lingual request:
• MDweb search application: SKOS thesaurus GEMET
http://cronos.geomatys.com:8280/wts/WS/thesaurus?
keyword=site&request=getConceptsMatchingKeyword&search_mode=4&language=fr&outputforma
t=RDF
request
http://cronos.geomatys.com:8280/wts/WS/thesaurus?
keyword=are&request=getConceptsMatchingKeyword&search_mode=4&language=en&outputform
at=RDF
request

35. Multi-lingual discovery
Example of a multi-lingual query:
• Part of request sent to the remote CSW
In UI Search module:‘espace protégé’
request ( title:(espace prot?g? OR protected area OR
Schutzgebiet OR espacios protegidos OR area protetta OR ?reas
protegidas) OR resume:(espace prot?g? OR protected area OR
Schutzgebiet OR espacios protegidos OR area protetta OR ?reas
protegidas) OR keywords:(espace prot?g? OR protected area OR
Schutzgebiet OR espacios protegidos OR area protetta OR ?reas
protegidas) OR generalterms:(espace prot?g? OR protected area
OR Schutzgebiet OR espacios protegidos OR area protetta OR
?reas protegidas) )

36. NatureSDI architecture example
Thesaurus
REMODELED DATA
Thesauri WS
Catalogue
Catalogue
Nature SDI CSW
National CSW
CSW Broker WMS Broker WFS Broker Download
WFSWMS
WMS WFS
DATA PROVIDER SERVICES
GEOPORTAL
REMODELED DATA
External
Thesaurus

37. Thesaurus
REMODELED DATA
Thesauri WS
Catalogue
Catalogue
Nature SDI CSW
National CSW
CSW Broker WMS Broker WFS Broker Download
WFSWMS
WMS WFS
DATA PROVIDER SERVICES
GEOPORTAL
REMODELED DATA
External
Thesaurus
NatureSDI architecture example

38. Web services for
data access

39. Data services
• Issue
– Publishing for access to harmonised information for each node
of a SDI
• Purpose
– Implement data publishing solution based on OGC/ISO
standards
• WMS: Web Map Service
• WFS: Web Feature Service
• Associated specifications: Filter encoding, SLD, WMC, …

40. WMS: Web Map Service
• Is a service interface specification that:
– Enables the dynamic construction of a map as a picture or as a series of
graphics elements, or as a packaged set of geographic features data
– Answers basic queries about the contents of the map
– Can inform others programs about the maps it can produce and provides
metadata about served data
‘A Web Map Service (WMS) is a web interface that allows one to
publish and deploy maps on the Internet’

41. WMS: Web Map Service
• Main operations
– GetCapabilities: Obtains the capabilities of the server using service-level
metadata. This is a description of the description of WMS information
content, list of layers provided, their extent, CRS, style;
– GetMap: Obtains the map (raster data or image file) whose geographic and
dimensional parameters should be defined by the data service provider’s
WMS;
– GetFeatureInfo: Obtains information about particular features shown on the
image or raster file.

42. WMS: Web Map Service
• Overview

43. WMS: Web Map Service
• Illustrations
http://demo20…/WS/wms?SERVICE=WMS& REQUEST=GetCapabilities
request
response
response
http://demo20…/WS/wms?SERVICE=WMS&
REQUEST=GetMap&VERSION=1.1.1&FORMAT=image/png& LAYERS=BlueMarble&
SRS=EPSG:3395& BBOX=-20000000,-20000000,20000000,20000000& WIDTH=600&
HEIGHT=600
request
response

44. WMS: Web Map Service
• Example of WMS web client for oceanography application
– Based on MapFaces framework (Tightly coupled Ajax/JSF)

45. WFS: Web Feature Service
The Web Feature Service (WFS) is an OGC specification which provides an
interface for describing data manipulation operations (create, update,
delete, get features) on geographic features using the HTTP protocol. WFS
exposes the data as GML.
Two kinds of WFS:
• Basic: read-only operations (get features)
• Transactional: data management. Must be associated with user-access
control

46. WFS: Web Feature Service
• Main operations
– Transactional WFS
• Provides operations to manage (create, update & delete operations) the
data repository. The mains operations are: Transaction, LockFeature
– Basic WFS
• GetCapabilities: Specifically, WFS indicates which feature types it can be
served, what operations are supported, what metadata are associated;
• GetFeature: retrieve the content of a simple feature. The response is an
XML that must conform to the GML application schema as defiined. The
client should be able to specify which feature properties to fetch.
• DescribeFeatureType: describe the structure of any feature type in a
XML schema. The client can request the server to detail the feature types
that it supports and their properties.

47. WFS: Web Feature Service
• Overview

48. WFS: Web Feature Service
• Illustrations
Voir message de mathieu
bossaert

49. Associated OGC specifications
Many others OGC specifications used to support specific needs, some of
them:
• Data Query specifications
– OGC filter encoding: filter expression in XML encoding used to identify
a subset of features
Example :
Query: « seek the road features with roadtype being equal to 1 »
SQL: « select * from roads where roadtype=1; »
OGC Filter: <Filter>
<PropertyIsEqualTo>
<PropertyName>roadtype</ PropertyName>
<Literal>1<Literal>
</PropertyIsEqualTo>
</Filter>
• Style specification
– Style Legend Descriptor (SLD): XM-based styling language to define how to
write a style rule. This rule is send to a WMS in order to draw a map.
Example:

50. References
‘Nature-GIS Guidelines, Data Infrastructures for protected areas’, Office for
official publications of the European Communities, EUR 21594 EN, ISBN
92-894-9399-2, 2005.