The metadata crisis: Can geographic information be made more usable?
Coordination of geographic information and geographic information systems Metadata.
Transcript of Coordination of geographic information and geographic information systems Metadata.
Coordination of geographic information and geographic information systems
Metadata
May 03COGIS Slide 2
www.e-geo.ch
May 03COGIS Slide 3
NSDI
Easy availableOptimal offer
Favorable pricesTransparency
ImpactPolitical economical profit
added value for:• public sector (Federal, Cantons, Communes)• organizations (private sector, science etc.)• General public
wider use
National Spatial Data Infrastructure (NSDI)
e-geo.chNetwork
Technicalinfrastructure
StandardsLegalbases
Strategy for distri-bution and pricing
MetadataBasic Geo-information
EducationTraining
Research
Basic Geo-services
May 03COGIS Slide 4
National Spatial Data Infrastructure (NSDI)
e-geo.chNetwork
Technicalinfrastructure
StandardsLegalbases
Strategy for distri-bution and pricing
MetadataBasic Geo-information
EducationTraining
Research
Basic Geo-services
Metadata is a part of the NSDI
May 03COGIS Slide 5
• geocat.ch– Concept– Timetable– Pilot application
• The metadata model for Switzerland– GeoMeta, the swiss profile of ISO 19115– Our model-based approach– Our experiences with the implementation
• Catalog gateway protocol– Goals– Overview– Query language
Outline
May 03COGIS Slide 6
geocat.ch concept (1)
• The geocat.ch project wants to set up a metadata catalogue for GI
• Geocat.ch will permit to add, edit, manage and to search for metadata on the Internet
• It will be realised as a framework of distributed metadata and applications in a federated and heterogeneous infrastructure.
Service de découverte geocat.ch
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geocat.ch concept (2)
User Interface /Discovery Service
CatalogGateway
Directory ofServers
(Registriy)
Metadata Spatial Data
catalogadministrator gateway
manager
useruses
maintains
complies
managesmanages
has reference to
posts a query to
searches multiple
deliever entries of
CatalogServer(s)
metadatacontributor
Source: GSDI Cookbook, Version 1.1
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geocat.ch concept (3)
2 type of database are connected:– One central database: the geocat.ch database, which is accessible
to the geocat.ch search application – Distributed databases, which are connected to the Catalog
Gateway of the geocat.ch search application
3 partnership possibilities exist for the producer of data:– Partner A: they manage their metadata directly in the central
database – Partner B: they manage their metadata in their own database. To
make their metadata accessible to the geocat.ch search application, they use the import/export tool to put them in the central database.
– Partner C: they manage their metadata in their own database. The metadata is accessible, because the database is connected to the Catalog Gateway
May 03COGIS Slide 9
Schedule of geocat.ch
Model Application
June to December 2001
Study of ISO 19115 and proposal of a profile for Switzerland
January to march 2002
Elicitation to 120 organisations, cantons and offices, 53 Reponses
April 2002 Workshop: presentation of the results of the elicitation
March to august 2002
A requirements specification is made with a group of 20 people (cantons, offices, organisation)
November 2002 Collaboration with Eurogeographics
December 2002 Choice of the producer and begin of the application development
May 2003 Pilot application is available
May 2003 A new draft of a ISO 19115 profile for Switzerland
June 2003 to ? Begin of a RFC (request for comments) and the standardisation process
September 2003 Catalog Gateway protocol will be defined
December 2003 Final application will be available
May 03COGIS Slide 10
Pilot application geocat.ch
May 03COGIS Slide 11
• geocat.ch– Concept– Timetable– Pilot application
• The metadata model for Switzerland– GeoMeta, the swiss profile of ISO 19115– Our model-based approach– Our experiences with the implementation
• Catalog gateway protocol– Goals– Overview– Query language
Outline
May 03COGIS Slide 12
GeoMeta the Swiss profile
• Based on ISO 19115• Additional requirements were derived from an analysis of
existing data catalogs (SIK-GIS and CDS)• ISO Standard covered most of these requirements• Swiss profile as presented at the workshop on May 22, 2002 in
Bangkok:– legal information is an additional metadata component– Multilingual support is essential (should be normative in
ISO 19115)– Several components and classes are not needed
• Since Bangkok workshop:– Model revised with the results from the elicitation and the
FDIS version
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Experience with implementation of GeoMeta (I)
ISO approach of Profiles– Profiles are reductions of a
general model– This approach proved to be not
feasible in our case– Local models are not necessary
based on common model
Swiss approach– Comprehensive Swiss profile is an
extension of the core profile– All additional models are derived
from the same base model
Comprehensive
CoreLocal
metadatamodel
Core
Comprehensive
Localmetadatamodel
Localmetadatamodel
Localmetadatamodel
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Experience with implementation of GeoMeta (II)
Responsible party can not be modeled as data type.– A specific party is responsible for several datasets– It can have different roles– Should only be stored and maintained once
Streetmap: MD_Identification
Rivermap: MD_Identification
Basemap-Metadata: MD_MetadataBasemap: MD_Identification
John: CI_ResponsibleParty
Individual Name: John DavisOrganisation Name: SwissTopo
Mary: CI_ResponsibleParty
Individual Name: Mary MillerOrganisation Name: Navtec
role: pointOfContactrole: custodian
role: distributerContact
role: owner
role: owner
May 03COGIS Slide 15
From UML to XML-Schema
• External classes were moved into 19115 package• All other packages were deleted• Multiplicity removed from attribute name and defined as a
tagged value• Data types reviewed and stereotype changed where needed to
fit the semantics predefined by UML• Export from Rational Rose to XMI• Import into UML/INTERLIS-Editor• Additional data type definitions• Export to XML-Schema
May 03COGIS Slide 16
Additional data type definition: Example
May 03COGIS Slide 17
• geocat.ch– Concept– Timetable– Pilot application
• The metadata model for Switzerland– GeoMeta, the swiss profile of ISO 19115– Our model-based approach– Our experiences with the implementation
• Catalog gateway protocol– Goals– Overview– Query language
Outline
May 03COGIS Slide 18
Goals of the protocol
• A catalog gateway protocol needs to be defined :– to manage a connection between the gateway application
(client) and an external server;– to be able to send a query from the client to the server;– for the client to be able to receive query results from the server.
• This query mechanism must be :– independent of the platform/system/vendor of both the client and
the server;– independent of the programming language used on either side;– independent of the network protocol used between the client and
the server;• The protocol must support multiple languages and spatial query
criteria • The protocol must be relatively cheap to implement
May 03COGIS Slide 19
Overview of the protocol
geocat.ch Server
OverviewQuery
OverviewAnswer
DetailQuery
DetailAnswer
• The OpenGIS Catalog Service and the Z39.50 protocols were considered to be too general for a cost effective implementation.
• SOAP (Simple Object Access Protocol) was chosen. It’s an XML based wrapping structure, like the postal services which use an envelope for letters that contain questions and answers.
May 03COGIS Slide 20
The query language of the protocol
Query language Description Price of the implementation
XQuery new and still unstable specification for the query of XML structures
too expensive for relational databases
SQL Standard query language for relational databases (suggested by the OpenGIS Catalog Service specifications)
too expensive for XML structures
geocat.ch solution
Only the needed functions exist
The query attributes are predefined
Cheap for the relational databases and the XML structures
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The geocat.ch query language solution example
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• The ISO 19115 standard covered most of our requirements
• A model-based approach : Comprehensive Swiss profile is an extension of the core profile
• To realise a framework of distributed metadata and applications in a federated and heterogeneous infrastructure, a catalog gateway protocol is necessary
Conclusion