LinkedGeoData and GeoKnow

LinkedGeoData and GeoKnow
Claus Stadler

Jens Lehmann

2013-09-19

Stadler, Lehmann (Univ. Leipzig)


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Outline
1

Motivation for LinkedGeoData

2

OpenStreetMap

3

LinkedGeoData Architecture

4

Sparqlify and Tag Mappings

5

Access and Statistics

6

Use Cases

7

GeoKnow Project Overview

8

GeoKnow Achievements



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Outline
1


2

OpenStreetMap

3


4


5


6

Use Cases

7


8




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Motivation

Ease

information integration

tasks that require

spatial knowledge,

such as

Oerings of bakeries next door
Map of distributed branches of a company
Historical sights along a bicycle track
LOD cloud contains data sets with spatial features
e.g. Geonames, DBpedia, US census, EuroStat
But: they are restricted to popular or large entities like countries,
famous places etc. or specic regions
Therefore

they lack


buildings, roads, mailboxes, etc.


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Outline
1


2

OpenStreetMap

3


4


5


6

Use Cases

7


8




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OpenStreetMap - Datamodel
Basic entities are:

Latitude, Longitude.
Sequence of nodes.
Relations Associations between any number of nodes, ways and
relations. Every member in a relation plays a certain role.
Each entity may be described with tags (= key-value pairs)
Nodes
Ways

A way is

closed if the ID of the last referenced node equals that of the

rst one.
Whether a closed way denotes a linear ring or a polygon (i.e. whether
the enclosed area is part of the respective OSM entity) depends on the
tags.



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Example: Leipzig's Zoo



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Comparison: Leipzig's Zoo (OpenStreetMap)



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Comparison: Leipzig's Zoo (GoogleMaps)



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Outline
1


2

OpenStreetMap

3


4


5


6

Use Cases

7


8




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LGD Architecture



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Tag Mappings

Key-value pairs will be assigned to
RDF ressources
Each pair

(k , v )

can be annotated with

datatypes, language tags, classes
Mappings are themselves tables
Example table:

k

lgd_map_literal

name
name:en
alt_label
note
...


property

rdfs:label
rdfs:label
skos:altLabel
rdfs:comment
...


lang
en
...

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View Denition

RDF mapping of the data from a
PostgreSQL database

Create View lgd_nodes As
Construct {
?n a lgdm:Node .
?n geom:geometry ?g .
?g ogc:asWKT ?o .
}
With
?n = uri(lgd:node, ?id)
?g = uri(lgd-geom:node, ?id)
?o = typedLiteral(?geom, ogc:wktLiteral)
From
nodes



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Sparqlify

SPARQL-SQL Rewriter

Rewrites SPARQL Queries according
to the view denition
Platform module oers SPARQL
Endpoint and Linked Data interface
https:
//github.com/AKSW/Sparqlify



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Rest-API

Oers REST methods for frequent
queries
Based on SPARQL (Virtuoso) endpoint



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Downloads

RDF dataset for download

Generated using

Construct { ?s ?p ?o }

http:
//downloads.linkedgeodata.org



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Outline
1


2

OpenStreetMap

3


4


5


6

Use Cases

7


8




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SML Mapping Examples

The following slides demonstrate how to map relational data to RDF
with the Sparqlication Mapping Language (SML).
Thereby, these prexes are used:

prex

rdfs
ogc
geom
lgd
lgd-geom

IRI

Prexes

http://www.w3.org/2000/01/rdf-schema#
http://www.opengis.net/ont/geosparql#
http://geovocab.org/geometry#
http://linkedgeodata.org/triplify/
http://linkedgeodata.org/geometry/



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SML - Mapping Example I: The Goal (1/4)
Input Table

id
1
2

How to map tables to RDF?

nodes

How to introduce the
commonly used
distinction in GIS between
feature and geometry?

geom

POINT(0 0)
POINT(1 1)

Aimed for RDF Output

@prefix rdfs: http://www.w3.org/2000/01/rdf-schema# .
...
lgd:node1 geom:geometry lgd-geom:node1 .
lgd-geom:node1 ogc:asWKT POINT(0 0)^^ogc:wktLiteral .



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SML - Mapping Example I: SML Syntax Outline (2/4)
Input Table

id
1
2

nodes

geom

POINT(0 0)
POINT(1 1)

Create View myNodesView As
Construct {
...
}
With
...
From
...


...



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SML - Mapping Example I: Construct and From (3/4)
Input Table

id
1
2

nodes

geom

POINT(0 0)
POINT(1 1)

Construct {
?g ogc:asWKT ?o
}
With
...
From
nodes


...


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SML - Mapping Example I: Complete! (4/4)
Input Table

id
1
2

nodes

geom

POINT(0 0)
POINT(1 1)

Construct {
?g ogc:asWKT ?o
}
With
?n = uri(lgd:node, ?id)
?g = uri(lgd-geom:node, ?id)
?o = typedLiteral(?geom,
ogc:wktLiteral)
From
nodes


...


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SML Mapping Examples

A more complex example, which demonstrates the use of an SQL
mapping table and an SQL helper view.



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SML - Mapping Example II: The Goal (1/8)
Input Table

id
1
1
1
1
1

node_tags

k

name
name:en
amenity
addr:street
addr:city

v

Universitaet Leipzig
University of Leipzig
university
Augustusplatz
Leipzig


@prefix lgd: http://linkedgeodata.org/triplify/ .
lgd:node1 rdfs:label Universitaet Leipzig .
lgd:node1 rdfs:label University of Leipzig@en .



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SML - Mapping Example II: Source Data (2/8)

OSM Table

id
1
1
1
1
1

node_tags

k

name
name:en
amenity
addr:street
addr:city

v

university
Augustusplatz
Leipzig



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SML - Mapping Example II: Mapping Table (3/8)

OSM Table

id
1
1
1
1
1

node_tags

k

name
name:en
amenity
addr:street
addr:city

RDF Mapping Table

v

university
Augustusplatz
Leipzig


k

lgd_map_literal

name
name:en
alt_label
note
...


property

rdfs:label
rdfs:label
skos:altLabel
rdfs:comment
...

lang
en
...

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SML - Mapping Example II: Helper View (4/8)
OSM Table

id

node_tags

1
1
1
1
1

k

name
name:en
amenity
addr:street
addr:city

RDF Mapping Table

v

university
Augustusplatz
Leipzig

k

lgd_map_literal

name
name:en
alt_label
note
...

property

rdfs:label
rdfs:label
skos:altLabel
rdfs:comment
...

lang
en
...

Helper View

lgd_node_tags_literal

id

1
1
...

property

rdfs:label
rdfs:label
...

v

...

lang
en
...

SELECT id, property, v, lang FROM node_tags, lgd_map_literal
WHERE node_tags.k

=

lgd_map_literal.k



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SML - Mapping Example II: SML View (5/8)

Logical Table

id

1
1
...

SML View


property

rdfs:label
rdfs:label
...

v

Univ. L.
Univ. of L.
...


lang
en
...

Create View lgd_node_tags_text As
Construct {


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Logical Table

id

1
1
...

SML View


property

rdfs:label
rdfs:label
...

v

Univ. L.
Univ. of L.
...


lang
en
...

Construct {
?s ?p ?o .
}
With
...
From


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Logical Table

id

1
1
...

SML View


property

rdfs:label
rdfs:label
...

v

Univ. L.
Univ. of L.
...


lang
en
...

Construct {
?s ?p ?o .
}
With
?s = uri(lgd:node, ?id)
?p = uri(?property)
?o = plainLiteral(?v, ?lang)
From


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Logical Table

SML View

+

Construct {
?s ?p ?o .
}
With
?s = uri(lgd:node, ?id)
?p = uri(?property)
?o = plainLiteral(?v, ?lang)
From

id

1
1
...


property

rdfs:label
rdfs:label
...

v

Univ. L.
Univ. of L.
...

lang
en
...

Resulting RDF

@prefix lgd: http://linkedgeodata.org/triplify/ .
lgd:node1 rdfs:label Universitaet Leipzig .
lgd:node1 rdfs:label University of Leipzig@en .



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Further Tag Mappings
decide datatype based on key:
lgd_map_dataype

k

seats
unisex

datatype
integer
boolean

decide property: based on key:
lgd_map_property

k

website

property

foaf:homepage

decide predicate and object based on key (e.g. class assertion):
lgd_map_resource_k

k

highway

property
rdf:type

object

lgdo:HighwayThing

decide predicate and object based on key and value:
lgd_map_resource_kv

k

waterway

v

river

property
rdf:type


object

lgdo:River


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LGD Edit Tool
Automatic heuristics for mappings
+ Multi user tag mapping web application for manual renements



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Ontology

Lightweight: taxonomy + domain/range axioms
1200+ classes
Enriched

classes and properties

with

multilingual labels

from

TranslateWiki

http://translatewiki.net
Imported

icons

for

90 classes

from the

freely available

icon

collection from the SJJB Management

http://www.sjjb.co.uk/mapicons/



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Outline
1


2

OpenStreetMap

3


4


5


6

Use Cases

7


8




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Resources

Sparqlify
http://sparqlify.org

LinkedGeoData
http://linkedgeodata.org

Tag Mappings
https://github.com/GeoKnow/LinkedGeoData/blob/master/linkedgeodata-core/src/main/resources/
org/aksw/linkedgeodata/sql/Mappings.sql

SML View Denitions
https://github.com/GeoKnow/LinkedGeoData/blob/master/linkedgeodata-core/src/main/resources/
org/aksw/linkedgeodata/sml/LinkedGeoData-Triplify-IndividualViews.sml



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Statistics (15 August 2013)
Complete OSM planet le corresponds to

∼

20.000.000.000 triples

Virtual access via Sparqlify
Full download: ca. 120 GB bz2 compressed (ca. 2.5 TB uncompressed)
2.7 MB ontology
Downloads for important fragments available (no roads etc.):

292.780.188 Triples

153.613.243 triples of Nodes
139.166.945 triples of Ways
Relations not yet available for download

Among them
532.812 PlaceOfWorship
82.788 RailwayStation
72.091 Toilets
71.613 Town
19.937 City



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Access
Materialized Sparql Endpoint

(based on Virtuoso DB, download

datasets loaded)

http://linkedgeodata.org/sparql
http://linkedgeodata.org/snorql

Virtual Sparql Endpoint

(based on Sparqlify, access to 20B triples,

limited SPARQL 1.0 support)

http://linkedgeodata.org/vsparql
http://linkedgeodata.org/vsnorql

Rest Interface (based on the Virtual Sparql Endpoint)
Supports limited queries (e.g. circular/rectangular area, ltering by
labels)
Downloads
http://downloads.linkedgeodata.org

Monthly updates on the above datasets envisioned


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Outline
1


2

OpenStreetMap

3


4


5


6

Use Cases

7


8




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Use Cases Augmented Reality



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Use Cases Generic Browsing



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Use Cases Generic Browsing



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App Generation



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Event Management



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Outline
1


2

OpenStreetMap

3


4


5


6

Use Cases

7


8




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Project Overview



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Outline
1


2

OpenStreetMap

3


4


5


6

Use Cases

7


8




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Achievements - Linked Data Stack
Many SW tools support one or
more life-cycle stages

Linked Data Stack (http:

Interlinking
/ Fusing

//stack.linkeddata.org)

Manual
revision/
Authoring

provides a consolidated
repository of such tools
Each tool is a

Debian

package

Classification/
Enrichment

Linked Data
Lifecycle

Storage/
Querying

Lightweight integration between

Quality
Analysis

tools via common vocabularies
and SPARQL

Evolution /
Repair

Extraction

Demonstrator interfaces for

Search/
Browsing/
Exploration

showing tools in combination
Developed by LOD2 and
GeoKnow


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Achievements - Benchmarking
Intensive work on benchmarking geospatial systems
Slippy map benchmark for standard web map applications and other
benchmarks to follow
State of the Art Analysis for Triple Stores performed (Virtuoso,
uSeekM, Parliament, AllegroGraph, OWLIM-SE, Strabon + Oracle
Spatial 11g, PostGIS as reference) using fragments of OSM and
Ordnance Survey data
High deviation in performance and supported functionality between
geospatial triple stores
GeoSPARQL compliance not achieved yet
More specic results to be published throughout the project . . .



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Achievements - Sparqlify

SPARQL-SQL rewriter
Rewrites a SPARQL query to a

single

SQL query allowing the

underlying database to perform optimizations
Improved extensibility of Sparqlify's model of the underlying database:
Custom SQL functions can now be programatically declared.
Web interface with syntax highlighting and live data generation for
easy mapping creation
Many bug xes, new optimizations (SQL, LEFT JOIN, ORDER BY)



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Achievements - LinkedGeoData
LinkedGeoData conversion simplied to a set of SQL les and
Sparqlify Mapping Denitions
Monthy dumps now working and automatically scheduled

1 2

LinkedGeoData and Sparqlify are available as Debian Packages!

1
2

https://github.com/AKSW/Sparqlify
https://github.com/GeoKnow/LinkedGeoData



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Achievements - TripleGeo

Converts shapeles /spatial DBMS output to RDF



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Achievements - Linking
Orthodromic distance only supported by LIMES and SILK
Linking algorithm ORCHID for geospatial data
Reduces number of comparisons
For DBpedia (threshold in kilometres):

Runtime (ms)

107

106
ORCHID
SILK

105

104

0.1

0.2

0.5

1

Threshold

Linking papers at ESWC'13 (linking + cloud, best paper award) and
ISWC'13 (ORCHID algorithm)


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Achievements - Facete
Generic faceted browser for HTTP SPARQL endpoints
Nested facets and client side pagination without pre-processing
Tested with up 10K spatial objects

→

Goal is to work with

DBpedia/LGD



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The End

Claus Stadler
cstadler@informatik.uni-leipzig.de
AKSW/Uni Leipzig

Jens Lehmann
lehmann@informatik.uni-leipzig.de
AKSW/Uni Leipzig

Geo

Know
http://geoknow.eu



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