spatial data infrastructure : issues and concepts

Spatial Data Infrastructure
Issues & Concepts
Jean-Christophe Desconnets
desconne@mpl.ird.fr

Change from specific information system…
Database
User
Buisiness
application
Non interoperable information system

To a distributed information system
user
Interoperables Information System
• normalized format
• Services, metadata
Internet

But …
The use of heterogeneous data, build with different :
• Acquisition protocol
• Coordinate reference system
• Accuracy
Geometric inconsistency

• Data model
• Legend and symbology
• In multi lingual and multi cultural vocabulary
Semantic inconsistency
And …

Concepts of Spatial Data
Infrastructure

What is SDI ?
« Spatial Data Infrastructure » (SDI) is used to encapsulate
the technologies, institutional arrangements, policies, that
facilitate the availability, access and effective usage of
geographical data ».
Based on a set of agreements on the technical, organisational
and legal issues to coordinate and administer SDI at the
differents levels (local > transnational)

Main Goal
• Provide
– access to harmonised geographic data for policy makers, planners
and managers, researchers, citizens and their organisations
– as means to respond in relevant and efficient way to
environmental questions (diagnosis, natural & industrial risks, ...)

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

Technical core components
• Content repositories
• Geographical data catalogues for viewing and manipulate :
– Data access
– Data/service query
– Gazetteer
– Portrayal
• Geo-processing services such as :
– coordinate transformation,
– image classification,
– Vectorial analysis
• User applications

Architecture reference model
Catalogues
Clients
Geo spatial
data
Geo spatial
data
Geo spatial
data
ServersDistributed
Content repositories
User applications
Metadata update
MiddleWare
services
Service chaining :
search, display,
access
Access to
transform data…
Metadata search &
retrieval for data
& services

Technical issues
• Adopt existing recognised standards in order to ensure
interoperability between components by developping and
providing interoperable geographic information services
• A common conceptual data model for transportation
networks, its encoding to provide data interoperable
according to standard methodologies.

What is a web service ?
• W3C defined as : «software applications identified by URI whose
interfaces and binding are capable of being defined, described and
discovered by XML artifacts and, support direct interactions with
others software applications using XML based messages via internet-
based protocols »
• Allow :
– To build highly distributed architecture. Each service is dedicated to a
specific task
– To access a set of well known services or a set of services that are
dynamically discovered and chained to solve a specific problem
• Geo-spatial web services deal with geographic information
– To provide access to geographical databases, perform queries, complex
computations and return geographical information. »

Web service Architecture
• Based upon interactions between 3 roles
Service
provider
User :
Service
requester
Registry:
Service
broker
Publish
Find
service
Bind
Service

What is interoperability ?
« the ability of disparate, heterogenous, distributed
computers, networks, operating systems and applications
to work together efficiently, without prior
communication, in order to exchange information in a
useful and meaningful manner »
Interoperability is the key to information sharing

Technical interoperability
Technical interoperability is the ability of different software systems
to communicate and interact through shared interfaces
At technical level, means building applications upon robust
industrial standards to provide an application with a well-
kown interfaces with robust semantic
such as OGC and ISO defined

Semantic interoperability
Semantic interoperability is the ability to search, find, access and use
geographic data produced at different times, by differents
organisations where differents naming shemes or differents reference
systems are used to describe features.
Depends largely on the use of standard naming schemes to
modelize and implement data
The main source of problem to share information
is the semantic heterogeneity frequently met in the same
community

International open
geographic standards
The toolbox for SDI

A toolbox to implement interoperability
Building on open standards provides interoperability
« Open standards are the results of consensus delivered by international
organisations and consortium, allow all actors in dedicated domains to
bring their experience to a global and semantic definition »
Main geographic standards as a framework to build interoperability :
– ISO standards : 19100 family (TC/211)
– OGC specifications
In conjonction with appropriate standards for underlying
technologies :
– W3C
– OMG

ISO
International Standard Organisation (ISO) is a world wide federation of
national standard bodies from 140 countries.
promote the development of the standardization to facilitate the international
exchanges.
Technical Comittee 211 (TC/211) aims to establish a structured set of
standards for information concerning objects, phenomena which are
directly/indirectly with associated to a location on the Earth
ISO standards may specify :
• Methods, tools and services for geographic data management (acquiring,
processing, analysing, accessing…) between different users, systems and
locations

ISO Standards
Most of them are involved in setting up of SDI :
Reference Model (ISO 19101) Conceptual Schema Language(ISO 19103)
Spatial Schema (ISO 19107) Temporal Schema (ISO 19107) ..
Metadata (ISO 19115) Services (ISO 19119) ISO 19110…
Profiles(ISO 19106) Rules for application schema (ISO 19109)
GML (ISO 1936) Metadata encoding (ISO 1939)

OGC
Open Geospatial Consortium (OGC), an international organisation, including
governemental, industrial and academic institutions, that focuses on
specifying interfaces for discover, access and use geographical data.
OGC specifications
are based on the need to seperate the interface of a system from its internal
working
give an interface model, not specific for a type of database or system
OGC/ISO relationships
• Work together to integrate and not duplicate the same specification in a way
to harmonise geographic information standards.
(OGC WMS specifications > ISO 19128 )

OGC specifications
The main specifications of OGC :
– Web Map Service (WMS) : operations to create and display map
– Web Feature Service (WFS) : operations for data manipulation on OGC
simple features
– Web Coverage Service (WCS) : extends WMS to allow access to
geographic «Coverages»
– Geographic Markup Language (GML) : XML encoding to transport &
store geographic information (geometry & properties)
– Catalogue Interface : interface that enables applications to perform
discover, browse and query operations against catalogs servers.
– Coordinate Transformation Service : for general positionning,
coordinate system and coordinate transformation

Others technical standards
Many non specific standards to geographic information are
involved in setting up a SDI.
• The World Wild Consortium (W3C) : develops technologies
(specifications, guidelines, software, …) to lead the web to its full potential.
Some of them :
– naming addressing technology URI/URL
– HTML, XHTML : language to publish content
– XML, XML schema : universal format to exchange information
– RDF, OWL as formal description of vocabulary/concepts to process
content of information through the web
• The Object Management Group (OMG) : not profit consortium that
produces and maintains computer industry specifications for enterprise
applications. The most important and more used :
– Unified Modelling language (UML) : helps to specify, visualize, and
document model (software, business data modelling). It’s helpful to
formalism and share concepts during a design step

Standards, software and interoperability
In distributed (service-oriented) architecture like a SDI, separate resources
don’t need to know how they each work
Need to have :
– Common ground to exchange messages without error or
misunderstanding
– Services interact with each other without encountering problems
bound to software solutions
Open standardised specifications is a way
to create this common ground

And data quality…
Inside a distributed system such as SDI is fundamental to use information to :
– Describe usability information
– Evaluate/test the data quality
Environmental information are collected at differents scales/units,
processed in numerous steps and various models. The result is :
– A propagation of error along the cycle of production
– A lake of information about accuracy

And data quality…
Nowadays, a gap between ISO 19113/19114 specifications (for
data producer) and users understanding
A Terminology more suitable must be develop to
integrate and use information about data quality

References
Gouvernance et pilotage
Utilisateurs
Producteurs
Stratégie / Objectifs
Données
Services
Applications
Infrastructure technique
• Nature-GIS Guidelines (2005) : Technical Guidelines for Spatial Data
Infrastructures for Protected Areas. Edited by Ioannis Kanellopoulos with the
contribution of Emmanuele Roccatagliata and Gorgio Saio. ISBN 92-894-9399-
2

spatial data infrastructure : issues and concepts

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