Coordination of geographic information and geographic information systems Metadata

May 03COGISSlide 2

May 03COGISSlide 3 NSDI Easy available Optimal offer Favorable prices Transparency Impact Political 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.ch Network Technical infrastructure Standards Legal bases Strategy for distri- bution and pricing Metadata Basic Geo- information Education Training Research Basic Geo- services

May 03COGISSlide 4 National Spatial Data Infrastructure (NSDI) e-geo.ch Network Technical infrastructure Standards Legal bases Strategy for distri- bution and pricing Metadata Basic Geo- information Education Training Research Basic Geo- services Metadata is a part of the NSDI

May 03COGISSlide 5 geocat.ch –Concept –Timetable –Pilot application The metadata model for Switzerland –GeoMeta, the swiss profile of ISO –Our model-based approach –Our experiences with the implementation Catalog gateway protocol –Goals –Overview –Query language Outline

May 03COGISSlide 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.

May 03COGISSlide 7 geocat.ch concept (2) Source: GSDI Cookbook, Version 1.1

May 03COGISSlide 8 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 03COGISSlide 9 Schedule of geocat.ch ModelApplication June to December 2001 Study of ISO and proposal of a profile for Switzerland January to march 2002 Elicitation to 120 organisations, cantons and offices, 53 Reponses April 2002Workshop: 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 2002Collaboration with Eurogeographics December 2002Choice of the producer and begin of the application development May 2003Pilot application is available May 2003A new draft of a ISO profile for Switzerland June 2003 to ?Begin of a RFC (request for comments) and the standardisation process September 2003Catalog Gateway protocol will be defined December 2003Final application will be available

May 03COGISSlide 10 Pilot application geocat.ch

May 03COGISSlide 11 geocat.ch –Concept –Timetable –Pilot application The metadata model for Switzerland –GeoMeta, the swiss profile of ISO –Our model-based approach –Our experiences with the implementation Catalog gateway protocol –Goals –Overview –Query language Outline

May 03COGISSlide 12 GeoMeta the Swiss profile Based on ISO 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

May 03COGISSlide 13 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

May 03COGISSlide 14 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

May 03COGISSlide 15 From UML to XML-Schema External classes were moved into 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 03COGISSlide 16 Additional data type definition: Example

May 03COGISSlide 17 geocat.ch –Concept –Timetable –Pilot application The metadata model for Switzerland –GeoMeta, the swiss profile of ISO –Our model-based approach –Our experiences with the implementation Catalog gateway protocol –Goals –Overview –Query language Outline

May 03COGISSlide 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 03COGISSlide 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 03COGISSlide 20 The query language of the protocol Query languageDescriptionPrice of the implementation XQuerynew and still unstable specification for the query of XML structures too expensive for relational databases SQLStandard 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

May 03COGISSlide 21 The geocat.ch query language solution example

May 03COGISSlide 22 The ISO 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