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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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Exploiting geo-data

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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

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