The emerge of Semantic Geoportals
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Transcript of The emerge of Semantic Geoportals
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The emerge of Semantic Geoportals
Athanasis Nikolaos
Konstantinos Kalabokidis
Vaitis Michail
Soulakellis Nikolaos
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Agenda
• Web portals and geo-portals• The Semantic Web• The emerge of semantic geo-portals• Related work• Summary & future work
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The World Wide Web today
• html
• web browsers
• hyperlinks
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Web Portals
Web Portal: A single point of access to information - a library of categorized and personalized content rich organization
of information
personalized content (customization)
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Geo-portals
Geo-portals: online access to collections of geospatial data
rich organization of information
rich organization of spatial information
interactive GIS mapping
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How geo-portals work
• Information providers: publishing GIS data and services
• Geo-portal: provides the rich organization of GIS data through its GUI
• GIS user community: searches the portal and exploits data of interest
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The role of metadata in geoportals
• Information providers publish metadata (descriptions about the data they want to share)
• The (catalog) geo-portal organizes the metadata in metadata records
• Users search the metadata records and
exploit data Or view metadata records
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publishing metadataSubmit metadata
through GUI
Metadata harvesting
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Geospatial metadata standards
• American Standard:– CSDGM (Content Standard for Digital Geospatial Metadata)
• European Standard:– CEN/TC287 (European Committee for Standardization )
• EN ISO 19115:2005
Metadata =
Identification_Information +
{Data_Quality_Information} +
{Spatial_Data_Organization_Information} +
{Spatial_Reference_Information} +
{Entity_and_Attribute_Information} +
{Distribution_Information}
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Current implications
• Lack of a uniform framework for describing geographic metadata– Deficiency to integrate / publishing metadata in geo-portals
• Current standards are unable to capture the data semantics they describe
• Semantic heterogeneity– Semantic conflicts in modeling - terminology (i.e. homonyms,
synonyms)– Insufficiency of XML (GML) to solve semantic discrepancies
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The Semantic Web• rich semantic organization
– ontologies (description schemata)
• RDFS, OWL
– resource descriptions
• RDF
• navigation based on conceptual relationships – semantic hyperlinks
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…and the geospatial Semantic Web• Development of spatial
ontologies and with a formal semantics
• Classification of geo-data under the appropriate classes of the ontologies
• Processing of geospatial queries against these semantic ontologies
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title
Metadata catalogs of a Semantic Geo- Portal in RDF
belongsToThemeEnumeration live data
Downloadabledocuments
ArcIMS service
Documents
Static documents
Map File
downloadablecontent
“….”
“…”
“…”
“…”
“vector”
publisher
description
on-linelinkage
spatial info
Metadatarecord
Feature serviceImage service
relatedcontent
serverURLString
title String
String
String
String
Enumeration
publisher
description
on-linelinkage
spatial info
&r1
&r2
&r3
relatedcontent
r1: www.geoportal.com/services/r1
downloadablecontent &r4
r2: www.geoportal.com/maps/r2
r3: www.geoportal.com/r3
r4: www.geoportal.com/download/r4
belongsToTheme
Natural Disasters
serverURL
“…”belongsToTheme
Natural Disasters
serverURL
“…”
Stringfile size
“…”
file size
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• Semantic navigation through– hierarchies of classes/properties– concept relationships– resources relationships
• semantic querying– data/schema querying– filtering conditions
• representation of geo-data– Mapping – Live data maps (Web Map Service- WMS)
• Publishing/representation of metadata according to spatial ontologies
Requirements for semantic geo-portals
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• expresses the semantic meaning of the geospatial resources using RDFS ontologies and RDF resource descriptions
• exploits a declarative query language (RQL) to resource descriptions
– filtering – on demand construction of RQL queries
• according to user navigation in the schema/data
Our solution
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Examples:• Find all image services about natural disasters as
well as related documents about them:
• Find the descriptions of the Map Files that you can download:
Our solution [cont]
select X1,X2
from {X1;Image_Service}related_content{X2;Documents},
{X1;Image_Service}belongsToTheme{X3}
where X3 = “Natural Disasters”
select W from
{;Map_Files}downloadable_content{X2;Downloadable_Documents},
{;Metadata_record}description{W}
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– Uses open source map tools• MapTools (image server)• WMS (GIS services)• php + apache (web server)
– Provides customization capabilities through the portlet framework of Jetspeed
Our solution [cont]
portlets: pluggable,
reusable components
of portal
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Related work
Semantic portals: ICS-FORTH Portal http://139.91.183.30:8999/
RQLdemo
geo-portals: Geospatial-One-Stop
http://gos2.geodata.gov/
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Summary
• Portals, geo-portals, metadata catalogs
• The current organization in geo-portal’s metadata catalogs is unable to capture the semantics of the data being described
• Semantic geo-portals: • organize their resources according to geospatial ontologies• exploit semantic query languages (RQL) to provide access to
information resources corresponding to the user’s navigation paths.
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Future Work
• Development of the appropriate geo-ontologies
• Design of the geo-portal system