In this paper we present LocLinkVis (Locate-Link-Visualize); a system which
supports exploratory information access to a document collection based on
geo-referencing and visualization. It uses a gazetteer which contains
representations of places ranging from countries to buildings, and that is used
to recognize toponyms, disambiguate them into places, and to visualize the
resulting spatial footprints.Comment: SEM'1

Claros, Rosa Merino

Kamps, Jaap

Olieman, Alex

English

arXiv

In this paper we present LocLinkVis (Locate-Link-Visualize); a system which supports exploratory information access to a document collection based on geo-referencing and visualization. It uses a gazetteer which contains representations of places ranging from countries to buildings, and that is used to recognize toponyms, disambiguate them into places, and to visualize the resulting spatial footprints

Olieman, A.

Kamps, J.

Merino Claros, R.

International Migration, Integration and Social Cohesion online publications

UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl)UvA-DARE (Digital Academic Repository)LocLinkVis: A Geographic Information Retrieval-Based System for Large-ScaleExploratory SearchOlieman, A.; Kamps, J.; Merino Claros, R.Publication date2015Document VersionFinal published versionPublished inPosters&Demos@SEMANTiCS 2015 : Posters&Demos@SEMANTiCS 2015 and DSci15WorkshopLink to publicationCitation for published version (APA):Olieman, A., Kamps, J., & Merino Claros, R. (2015). LocLinkVis: A Geographic InformationRetrieval-Based System for Large-Scale Exploratory Search. In A. Filipowska, R. Verborgh, &A. Polleres (Eds.), Posters&Demos@SEMANTiCS 2015 : Posters&Demos@SEMANTiCS2015 and DSci15 Workshop: Joint Proceedings of the Posters and Demos Track of 11thInternational Conference on Semantic Systems - SEMANTiCS2015 and 1st Workshop onData Science: Methods, Technology and Applications (DSci15), co-located with the 11thInternational Conference on Semantic Systems - SEMANTiCS2015 : Vienna, Austria,September 15-17, 2015 (pp. 30-33). (CEUR Workshop Proceedings; Vol. 1481). CEUR-WS.http://ceur-ws.org/Vol-1481/paper9.pdfGeneral rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s)and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an opencontent license (like Creative Commons).Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, pleaselet the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the materialinaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letterto: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. Youwill be contacted as soon as possible.Download date:10 Mar 2023LocLinkVis: a Geographic Information Retrieval-BasedSystem for Large-Scale Exploratory SearchAlex OliemanUniversity of Amsterdamolieman@uva.nlJaap KampsUniversity of Amsterdamkamps@uva.nlRosa Merino ClarosUniversity of Amsterdamr.merinoclaros@uva.nlABSTRACTIn this paper we present LocLinkVis (Locate-Link-Visualize);a system which supports exploratory information access toa document collection based on geo-referencing and visual-ization. It uses a gazetteer which contains representations ofplaces ranging from countries to buildings, and that is usedto recognize toponyms, disambiguate them into places, andto visualize the resulting spatial footprints.KeywordsGeographic Information Retrieval, Exploratory Search, Geo-Referencing, Interactive Visualization, OpenStreetMap1. INTRODUCTIONThe present day Web search interaction model of typing asimple keyword query and glancing over a list of 10 blue linkshas not satisfied the needs of (re)searchers who deal withlarge (thematic) collections. In the cultural heritage andlegal domains, for instance, information needs that cannotbe answered by any single document, but require comparingseveral documents or an overview of documents that satisfythe query, are quite common.One important direction for improving access to sufficientlylarge collections, such as those curated by archives and li-braries, is geo-referencing: linking information to geographi-cal location [3]. Links from documents to geospatial entitiescan be indexed by a search system, allowing users to freelyexplore the geographical aspect of the collection, or to viewthe results of a thematic query on a map. This is an impor-tant next step in making digital cultural heritage collectionsmore accessible to scholars in various branches of the hu-manities [7]. Furthermore, the most common types of inter-action that today’s users have with digital maps, pan andzoom, translate exceptionally well to existing exploratorysearch strategies: shift and narrow [5].Existing Geographic Information Retrieval (GIR) systemsdesigned for archives, however, are limited by their represen-tation of locations. These systems represent place as point(i.e. a single latitude-longitude pair) [2, 3], which uncontest-edly simplifies the technical requirements of the system, butalso limits the possibilities for the meaningful visualizationof document results. We argue that there is more to visualiz-ing a mentioned location than a single point. Qualitatively,it can make a big difference whether someone speaks abouta country, region, municipality, metropolis, highway, town,square, street, school, restaurant, or monument. How canthis difference be shown in the visualization? We proposea deceptively simple answer to this question: by displayingthe same geometry that is used to represent these locationson a map.In this paper we present LocLinkVis; a system which sup-ports exploratory information access to a document collec-tion based on geo-referencing and visualization. It uses agazetteer which contains representations of places rangingfrom countries to buildings, and which is used to recognizetoponyms, disambiguate them into places, and to visualizethe resulting spatial footprints. OpenStreetMap1 (OSM) isthe only data source that is needed to fill the gazetteer.Our current LocLinkVis prototype covers the Netherlandsand neighboring regions, but it can easily be populated byarbitrary subsets of OSM data (which has planet-wide cov-erage2). The current prototype runs comfortably on a com-modity laptop, but would benefit from more powerful hard-ware if it were to provide global coverage. For the document-side of the system our proof-of-concept focuses on existingdigital collections of parliamentary proceedings from Canada,the Netherlands, and the United Kingdom. The currentLocLinkVis prototype is limited to a Dutch gazetteer andcorpus, but will soon be expanded with the Canadian andUK corpora to match the coverage of the general Political-Mashup3 search engine.2. SYSTEM ARCHITECTUREThe systems design of LocLinkVis originates from the fol-lowing requirements. The system should efficiently:1. detect toponyms ranging from countries to buildings;2. disambiguate which geographical features the toponymsrefer to;3. build an index of documents by the locations theymention;4. use a map interface’s viewport and zoom level as queryparameters;5. visualize results on a map, at a suitable level of ab-straction.Figure 1 shows the components of the resulting system, andwhich communication occurs between them. The numbers1http://www.openstreetmap.org/2See https://tyrasd.github.io/osm-node-density/forOSM’s coverage in 20143http://search.politicalmashup.nl30Figure 1: Schematic overview of LocLinkVis’ system architecture.in this schematic indicate which requirement is satisfied in(or between) which part(s) of the system.The gazetteer builder takes OSM data as input, in theform of efficient binary dumps as well as incremental XMLupdates. Its primary purpose is to transform OSM’s nor-malized (i.e. with internal references) Node, Way, and Rela-tion instances to denormalized GeoJSON4 features. ThisJSON-based format for geospatial data structures is bet-ter suited towards retrieving and rendering spatial data,whereas OSM’s data schema favors editing it. Second, whilethe OSM data is being imported, instances of the same geo-graphical type (e.g. city or road) that share a toponym andgeometrically intersect, are merged into a single gazetteerfeature. OSM contains data at fine level of granularity, e.g.to indicate that a particular road section goes through a tun-nel. Our aim is to simplify (the side-effects of) such detailswhen they are undesirable for spatial document search.Our gazetteer, like its paper media predecessors, providesan easily searchable list of toponyms, each accompaniedby facts about its location amongst other aspects. Mod-ern gazetteers, such as the Getty Thesaurus of GeographicNames5, commonly represent the location of places as co-ordinate pairs. With thanks to the OSM contributors, wecan now provide detailed geometries for the features in ourgazetteer. Besides the data that is copied and denormalizedfrom OSM, we add to each feature the identifiers of the OSMinstances it was derived from, and build an index of featuresby all their known names (including historic toponyms).Toponym detection entails identifying which tokens froman input document refer to a place. LocLinkVis takes alexicon-based approach in which all known toponyms fromthe gazetteer are encoded into a finite state automaton bythe Aho-Corasick algorithm [1]. This allows for efficient4http://geojson.org/geojson-spec.html5http://www.getty.edu/research/tools/vocabularies/tgn/string matching between an input document and a large setof toponyms. At this stage the detected phrases are candi-date toponyms, which may or may not refer to a gazetteerfeature.NIL detection is the process by which candidate toponymsmay be identified as not-referring to any location that is rep-resented in the gazetteer. We opted for a corpus-independentapproach, which starts by counting the frequency with whichtoponyms from the gazetteer are mentioned in a Wiktionary6dump of the desired language. Wiktionary, for this purpose,serves as a compact, but high-coverage, cross section of lex-ical forms within a language. Possible toponyms that arementioned frequently, it seems safe to assume, refer eitherto well-known places or are homographs of common wordsor other names. LocLinkVis uses Support Vector Machinesthat have been trained on a small number of training ex-amples to make this distinction. Besides Wiktionary oc-currence, the feature space that is used for classification in-cludes variables obtained from SPARQL queries to DBpedia,as well as queries to the gazetteer.Location type classification takes the lexical context ofmentioned toponyms into account for disambiguation. Itcomputes for any toponym (not limited to our gazetteer)the probabilities that it refers to an instance of the typesCountry, Province, (body of) Water, Municipality, Neigh-borhood, Road, and Building. It does so on the basis of awindow of five tokens preceding and following the toponymin question. Numerical tokens are replaced by a normalizedform. The same is done for other toponyms within the to-ken window in the training examples, and for unambiguoustoponyms in unseen input. LocLinkVis offers the choice be-tween a Naive Bayes and a Maximum Entropy classifier, anduses between 25 and 85 training examples per class.Spatial analysis is useful to operationalize Tobler’s “firstlaw of geography,” that “everything is related to everything6https://www.wiktionary.org/31Figure 2: Slippy map with highlighted places that are mentioned in context of the Rotterdam harbor.Figure 3: Timeline widget showing the number of results for current Dutch government parties, with aselection of the period 1978-1987.else, but near things are more related than distant things.”[4] By taking into account the spatial distance between can-didate entities, we investigate the hypothesis that nearerfeatures are more frequently mentioned together than dis-tant features. A relatedness measure such as distance canbe used with existing methods to collectively rank candidateentities [6]. We employ a graph-based method, using ran-dom walkers to traverse a fully-connected weighted graph offeatures, to rank candidates. The next step, at the time ofwriting, is to explore how to integrate the spatial and lexicalparts of our disambiguation approach.The geo-demo user interface (UI), available athttp://geodemo.politicalmashup.nl, allows users to in-teractively validate our geo-referencing approach. Using thisUI, arbitrary text can be submitted to the geospatial webserver to view the intermediate results at each stage of thegeo-referencing process. It shows which toponyms have beendetected, which are thought not to be represented in thegazetteer, and the (detailed) output of location type clas-sification and spatial analysis for all candidate features. Aslippy map7 covers the screen, with input fields and geo-referencing details being available from an expandable menu.7http://wiki.openstreetmap.org/wiki/Slippy_MapThe search engine provides indexed access to one or moredocument collections. In our particular case these are cor-pora of national parliamentary proceedings in the rich Po-liticalMashup XML format, but plain text documents wouldalso be sufficient. In order to enrich a document with geospa-tial annotations, the text it contains is submitted to thegeospatial web server, which returns annotations of the form<Feature URI, Span, Confidence, Bounding Box>.A geospatial index ensures that the search engine can bequeried with an arbitrary bounding box, and return docu-ments from which any of the annotated locations intersectwith the bounding box. If the documents also feature a tem-poral property (e.g. creation date or period of activity), itcan enable further meaningful filtering of the results.LocLinkVis’ search UI is described in the following section.3. SEARCH UI DESIGNThe main aim of our search UI is to provide an interac-tive geospatial overview of document results. In contrastto traditional GIR systems, which have focused on associat-ing documents with a single location (often in the form ofa point), this UI displays all places that are mentioned inthe documents (see Figure 2), and with the same fidelity towhich they are rendered on the background map. To assistin searching document collections with an interesting tem-32poral aspect, we have added a timeline widget which furtherfilters the result set.The timeline widget, see Figure 3, shows the number ofplaces that are mentioned in the result set and intersectwith the map viewport. A categorical variable (i.e. facet)can be used to break the total frequency down into resultcategories. The user may make a selection on this timeline,which acts as a temporal filter within the larger query. Ad-ditionally, besides manual adjustment of the selected timeperiod, controls are provided which enable moving windowplayback which shows the dynamic of how often places werementioned through time.By these means the search UI provides a bidirectional bind-ing between the spatial and temporal aspects for the explo-ration of a search result set. When a user interacts withthe slippy map (i.e. by panning and zooming), the chart inthe timeline widget is updated to reflect the new viewport.Vice versa, when a time period is selected or adjusted, thesearch result set is (re-)filtered and the highlighted locationson the map are updated accordingly. This enables the userto seamlessly move between shift and narrow search strate-gies, as well as between the spatial and temporal dimensionsof the result space.The search UI is under active (iterative) development at thetime of writing. Hence, our prototype at http://geosearch.politicalmashup.nl will be changed periodically and maynot always be available. We are, for instance, currently ex-perimenting with the placement of result snippets in theinterface. When a user clicks a highlighted location, docu-ment results from a query could either be displayed on ornear the clicked location, or be shown within a fixed screenarea.4. CONCLUSION AND OUTLOOKIn this paper a novel GIR-based system was presented thatsupports exploratory information access to a document col-lection by means of geo-referencing and interactive visualiza-tion. LocLinkVis distinguishes itself from existing systemsthat have similar goals by working with a broader range oflocation types, and by representing a location’s geometrywith the same fidelity as to which it is rendered on Open-StreetMap. It also features a UI which allows the user toseamlessly move between the shift and narrow search strate-gies, as well as between the spatial and temporal dimensionsof the result space.This work is situated in the context of a project which aimsto improve (exploratory) information access to parliamen-tary proceedings and related cultural heritage collections.We are working towards a living lab with high-quality, reli-able prototype systems and ubiquitous interaction logging.This approach allows us to use a combination of (remote)laboratory experiments and analysis of in-the-wild usage toinvestigate how we can best assist historians, political scien-tists, journalists, and media scholars in their complex searchand sensemaking activities.Our current effort to provide accurate results for histori-cal collections mainly consists of collecting historical placenames from OSM, e.g. to compensate for spelling variantsin older texts. The gazetteer, however, does not yet containinformation about during which time period a place wasknown by a particular name, and only contains the mostrecent geometric representation that is available. This canlead to a distorted picture e.g. when borders have changedmuch, or when a monument has not always been in itspresent-day location. At least for Dutch municipalities theinformation needed to display the historical situation accu-rately is available [8], and we plan to adapt the gazetteerbuilder to incorporate it.Acknowledgements This research was supported by theNetherlands Organization for Scientific Research (ExPoSeproject, NWO CI # 314.99.108; DiLiPaD project, NWODigging into Data # 600.006.014). We would like to thankthe anonymous reviewers of this paper for their useful re-marks.5. REFERENCES[1] A. V. Aho and M. J. Corasick. Efficient stringmatching: an aid to bibliographic search.Communications of the ACM, 18:333–340, 1975.[2] L. Borin, D. Dannells, and L.-J. Olsson. Geographicvisualization of place names in Swedish literary texts.Literary and Linguistic Computing, 29(3):400–404, May2014.[3] P. Clough, J. Tang, M. M. Hall, and A. Warner.Linking archival data to location: a case study at theUK National Archives. Aslib Proceedings,63(2/3):127–147, 2011.[4] H. J. Miller. Tobler’s First Law and Spatial Analysis.Annals of the Association of American Geographers,94(2):284–289, 2004.[5] K. Samp, C. Bezuit, and J. Schneider. Unifying theShift and Narrow Strategies in Focus + ContextExploratory Search. In Proc. of SIGDOC 2014,Colorado Springs, CO, USA, 2014. ACM.[6] W. Shen, J. Wang, and J. Han. Entity Linking with aKnowledge Base: Issues, Techniques, and Solutions.IEEE Transactions on Knowledge and DataEngineering, 4347(2):443–460, 2014.[7] R. Simon, E. Barker, L. Isaksen, andP. de Soto Cañamares. Linking early geospatialdocuments, one place at a time: Annotation ofgeographic documents with recogito. e-Perimetron,10(2):49–59, 2015.[8] I. Zandhuis, M. den Engelse, and E. Mac Gillavry.Dutch historical toponyms in the Semantic Web. InProc. Workshop Population Reconstruction, 2014.33

LocLinkVis: A Geographic Information Retrieval-Based System for Large-Scale Exploratory Search

UvA-DARE is a service provided by the library of the University of Amsterdam (http://dare.uva.nl)
UvA-DARE (Digital Academic Repository)
LocLinkVis: A Geographic Information Retrieval-Based System for Large-Scale Exploratory
Search
Olieman, A.; Kamps, J.; Merino Claros, R.
Published in:
CEUR Workshop Proceedings
Link to publication
Citation for published version (APA):
Olieman, A., Kamps, J., & Merino Claros, R. (2015). LocLinkVis: A Geographic Information Retrieval-Based
System for Large-Scale Exploratory Search. CEUR Workshop Proceedings, 1481, 30-33. http://ceur-ws.org/Vol-
1481/paper9.pdf
General rights
It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s),
other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons).
Disclaimer/Complaints regulations
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating
your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask
the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam,
The Netherlands. You will be contacted as soon as possible.
Download date: 05 Feb 2021
LocLinkVis: a Geographic Information Retrieval-Based
System for Large-Scale Exploratory Search
Alex Olieman
University of Amsterdam
olieman@uva.nl
Jaap Kamps
University of Amsterdam
kamps@uva.nl
Rosa Merino Claros
University of Amsterdam
r.merinoclaros@uva.nl
ABSTRACT
In this paper we present LocLinkVis (Locate-Link-Visualize);
a system which supports exploratory information access to
a document collection based on geo-referencing and visual-
ization. It uses a gazetteer which contains representations of
places ranging from countries to buildings, and that is used
to recognize toponyms, disambiguate them into places, and
to visualize the resulting spatial footprints.
Keywords
Geographic Information Retrieval, Exploratory Search, Geo-
Referencing, Interactive Visualization, OpenStreetMap
1. INTRODUCTION
The present day Web search interaction model of typing a
simple keyword query and glancing over a list of 10 blue links
has not satisfied the needs of (re)searchers who deal with
large (thematic) collections. In the cultural heritage and
legal domains, for instance, information needs that cannot
be answered by any single document, but require comparing
several documents or an overview of documents that satisfy
the query, are quite common.
One important direction for improving access to sufficiently
large collections, such as those curated by archives and li-
braries, is geo-referencing: linking information to geographi-
cal location [3]. Links from documents to geospatial entities
can be indexed by a search system, allowing users to freely
explore the geographical aspect of the collection, or to view
the results of a thematic query on a map. This is an impor-
tant next step in making digital cultural heritage collections
more accessible to scholars in various branches of the hu-
manities [7]. Furthermore, the most common types of inter-
action that today’s users have with digital maps, pan and
zoom, translate exceptionally well to existing exploratory
search strategies: shift and narrow [5].
Existing Geographic Information Retrieval (GIR) systems
designed for archives, however, are limited by their represen-
tation of locations. These systems represent place as point
(i.e. a single latitude-longitude pair) [2, 3], which uncontest-
edly simplifies the technical requirements of the system, but
also limits the possibilities for the meaningful visualization
of document results. We argue that there is more to visualiz-
ing a mentioned location than a single point. Qualitatively,
it can make a big difference whether someone speaks about
a country, region, municipality, metropolis, highway, town,
square, street, school, restaurant, or monument. How can
this difference be shown in the visualization? We propose
a deceptively simple answer to this question: by displaying
the same geometry that is used to represent these locations
on a map.
In this paper we present LocLinkVis; a system which sup-
ports exploratory information access to a document collec-
tion based on geo-referencing and visualization. It uses a
gazetteer which contains representations of places ranging
from countries to buildings, and which is used to recognize
toponyms, disambiguate them into places, and to visualize
the resulting spatial footprints. OpenStreetMap1 (OSM) is
the only data source that is needed to fill the gazetteer.
Our current LocLinkVis prototype covers the Netherlands
and neighboring regions, but it can easily be populated by
arbitrary subsets of OSM data (which has planet-wide cov-
erage2). The current prototype runs comfortably on a com-
modity laptop, but would benefit from more powerful hard-
ware if it were to provide global coverage. For the document-
side of the system our proof-of-concept focuses on existing
digital collections of parliamentary proceedings from Canada,
the Netherlands, and the United Kingdom. The current
LocLinkVis prototype is limited to a Dutch gazetteer and
corpus, but will soon be expanded with the Canadian and
UK corpora to match the coverage of the general Political-
Mashup3 search engine.
2. SYSTEM ARCHITECTURE
The systems design of LocLinkVis originates from the fol-
lowing requirements. The system should efficiently:
1. detect toponyms ranging from countries to buildings;
2. disambiguate which geographical features the toponyms
refer to;
3. build an index of documents by the locations they
mention;
4. use a map interface’s viewport and zoom level as query
parameters;
5. visualize results on a map, at a suitable level of ab-
straction.
Figure 1 shows the components of the resulting system, and
which communication occurs between them. The numbers
1http://www.openstreetmap.org/
2See https://tyrasd.github.io/osm-node-density/for
OSM’s coverage in 2014
3http://search.politicalmashup.nl
30
Figure 1: Schematic overview of LocLinkVis’ system architecture.
in this schematic indicate which requirement is satisfied in
(or between) which part(s) of the system.
The gazetteer builder takes OSM data as input, in the
form of efficient binary dumps as well as incremental XML
updates. Its primary purpose is to transform OSM’s nor-
malized (i.e. with internal references) Node, Way, and Rela-
tion instances to denormalized GeoJSON4 features. This
JSON-based format for geospatial data structures is bet-
ter suited towards retrieving and rendering spatial data,
whereas OSM’s data schema favors editing it. Second, while
the OSM data is being imported, instances of the same geo-
graphical type (e.g. city or road) that share a toponym and
geometrically intersect, are merged into a single gazetteer
feature. OSM contains data at fine level of granularity, e.g.
to indicate that a particular road section goes through a tun-
nel. Our aim is to simplify (the side-effects of) such details
when they are undesirable for spatial document search.
Our gazetteer, like its paper media predecessors, provides
an easily searchable list of toponyms, each accompanied
by facts about its location amongst other aspects. Mod-
ern gazetteers, such as the Getty Thesaurus of Geographic
Names5, commonly represent the location of places as co-
ordinate pairs. With thanks to the OSM contributors, we
can now provide detailed geometries for the features in our
gazetteer. Besides the data that is copied and denormalized
from OSM, we add to each feature the identifiers of the OSM
instances it was derived from, and build an index of features
by all their known names (including historic toponyms).
Toponym detection entails identifying which tokens from
an input document refer to a place. LocLinkVis takes a
lexicon-based approach in which all known toponyms from
the gazetteer are encoded into a finite state automaton by
the Aho-Corasick algorithm [1]. This allows for efficient
4http://geojson.org/geojson-spec.html
5http://www.getty.edu/research/tools/vocabularies/
tgn/
string matching between an input document and a large set
of toponyms. At this stage the detected phrases are candi-
date toponyms, which may or may not refer to a gazetteer
feature.
NIL detection is the process by which candidate toponyms
may be identified as not-referring to any location that is rep-
resented in the gazetteer. We opted for a corpus-independent
approach, which starts by counting the frequency with which
toponyms from the gazetteer are mentioned in a Wiktionary6
dump of the desired language. Wiktionary, for this purpose,
serves as a compact, but high-coverage, cross section of lex-
ical forms within a language. Possible toponyms that are
mentioned frequently, it seems safe to assume, refer either
to well-known places or are homographs of common words
or other names. LocLinkVis uses Support Vector Machines
that have been trained on a small number of training ex-
amples to make this distinction. Besides Wiktionary oc-
currence, the feature space that is used for classification in-
cludes variables obtained from SPARQL queries to DBpedia,
as well as queries to the gazetteer.
Location type classification takes the lexical context of
mentioned toponyms into account for disambiguation. It
computes for any toponym (not limited to our gazetteer)
the probabilities that it refers to an instance of the types
Country, Province, (body of) Water, Municipality, Neigh-
borhood, Road, and Building. It does so on the basis of a
window of five tokens preceding and following the toponym
in question. Numerical tokens are replaced by a normalized
form. The same is done for other toponyms within the to-
ken window in the training examples, and for unambiguous
toponyms in unseen input. LocLinkVis offers the choice be-
tween a Naive Bayes and a Maximum Entropy classifier, and
uses between 25 and 85 training examples per class.
Spatial analysis is useful to operationalize Tobler’s “first
law of geography,” that “everything is related to everything
6https://www.wiktionary.org/
31
Figure 2: Slippy map with highlighted places that are mentioned in context of the Rotterdam harbor.
Figure 3: Timeline widget showing the number of results for current Dutch government parties, with a
selection of the period 1978-1987.
else, but near things are more related than distant things.”
[4] By taking into account the spatial distance between can-
didate entities, we investigate the hypothesis that nearer
features are more frequently mentioned together than dis-
tant features. A relatedness measure such as distance can
be used with existing methods to collectively rank candidate
entities [6]. We employ a graph-based method, using ran-
dom walkers to traverse a fully-connected weighted graph of
features, to rank candidates. The next step, at the time of
writing, is to explore how to integrate the spatial and lexical
parts of our disambiguation approach.
The geo-demo user interface (UI), available at
http://geodemo.politicalmashup.nl, allows users to in-
teractively validate our geo-referencing approach. Using this
UI, arbitrary text can be submitted to the geospatial web
server to view the intermediate results at each stage of the
geo-referencing process. It shows which toponyms have been
detected, which are thought not to be represented in the
gazetteer, and the (detailed) output of location type clas-
sification and spatial analysis for all candidate features. A
slippy map7 covers the screen, with input fields and geo-
referencing details being available from an expandable menu.
7http://wiki.openstreetmap.org/wiki/Slippy_Map
The search engine provides indexed access to one or more
document collections. In our particular case these are cor-
pora of national parliamentary proceedings in the rich Po-
liticalMashup XML format, but plain text documents would
also be sufficient. In order to enrich a document with geospa-
tial annotations, the text it contains is submitted to the
geospatial web server, which returns annotations of the form
<Feature URI, Span, Confidence, Bounding Box>.
A geospatial index ensures that the search engine can be
queried with an arbitrary bounding box, and return docu-
ments from which any of the annotated locations intersect
with the bounding box. If the documents also feature a tem-
poral property (e.g. creation date or period of activity), it
can enable further meaningful filtering of the results.
LocLinkVis’ search UI is described in the following section.
3. SEARCH UI DESIGN
The main aim of our search UI is to provide an interac-
tive geospatial overview of document results. In contrast
to traditional GIR systems, which have focused on associat-
ing documents with a single location (often in the form of
a point), this UI displays all places that are mentioned in
the documents (see Figure 2), and with the same fidelity to
which they are rendered on the background map. To assist
in searching document collections with an interesting tem-
32
poral aspect, we have added a timeline widget which further
filters the result set.
The timeline widget, see Figure 3, shows the number of
places that are mentioned in the result set and intersect
with the map viewport. A categorical variable (i.e. facet)
can be used to break the total frequency down into result
categories. The user may make a selection on this timeline,
which acts as a temporal filter within the larger query. Ad-
ditionally, besides manual adjustment of the selected time
period, controls are provided which enable moving window
playback which shows the dynamic of how often places were
mentioned through time.
By these means the search UI provides a bidirectional bind-
ing between the spatial and temporal aspects for the explo-
ration of a search result set. When a user interacts with
the slippy map (i.e. by panning and zooming), the chart in
the timeline widget is updated to reflect the new viewport.
Vice versa, when a time period is selected or adjusted, the
search result set is (re-)filtered and the highlighted locations
on the map are updated accordingly. This enables the user
to seamlessly move between shift and narrow search strate-
gies, as well as between the spatial and temporal dimensions
of the result space.
The search UI is under active (iterative) development at the
time of writing. Hence, our prototype at http://geosearch.
politicalmashup.nl will be changed periodically and may
not always be available. We are, for instance, currently ex-
perimenting with the placement of result snippets in the
interface. When a user clicks a highlighted location, docu-
ment results from a query could either be displayed on or
near the clicked location, or be shown within a fixed screen
area.
4. CONCLUSION AND OUTLOOK
In this paper a novel GIR-based system was presented that
supports exploratory information access to a document col-
lection by means of geo-referencing and interactive visualiza-
tion. LocLinkVis distinguishes itself from existing systems
that have similar goals by working with a broader range of
location types, and by representing a location’s geometry
with the same fidelity as to which it is rendered on Open-
StreetMap. It also features a UI which allows the user to
seamlessly move between the shift and narrow search strate-
gies, as well as between the spatial and temporal dimensions
of the result space.
This work is situated in the context of a project which aims
to improve (exploratory) information access to parliamen-
tary proceedings and related cultural heritage collections.
We are working towards a living lab with high-quality, reli-
able prototype systems and ubiquitous interaction logging.
This approach allows us to use a combination of (remote)
laboratory experiments and analysis of in-the-wild usage to
investigate how we can best assist historians, political scien-
tists, journalists, and media scholars in their complex search
and sensemaking activities.
Our current effort to provide accurate results for histori-
cal collections mainly consists of collecting historical place
names from OSM, e.g. to compensate for spelling variants
in older texts. The gazetteer, however, does not yet contain
information about during which time period a place was
known by a particular name, and only contains the most
recent geometric representation that is available. This can
lead to a distorted picture e.g. when borders have changed
much, or when a monument has not always been in its
present-day location. At least for Dutch municipalities the
information needed to display the historical situation accu-
rately is available [8], and we plan to adapt the gazetteer
builder to incorporate it.
Acknowledgements This research was supported by the
Netherlands Organization for Scientific Research (ExPoSe
project, NWO CI # 314.99.108; DiLiPaD project, NWO
Digging into Data # 600.006.014). We would like to thank
the anonymous reviewers of this paper for their useful re-
marks.
5. REFERENCES
[1] A. V. Aho and M. J. Corasick. Efficient string
matching: an aid to bibliographic search.
Communications of the ACM, 18:333–340, 1975.
[2] L. Borin, D. Dannells, and L.-J. Olsson. Geographic
visualization of place names in Swedish literary texts.
Literary and Linguistic Computing, 29(3):400–404, May
2014.
[3] P. Clough, J. Tang, M. M. Hall, and A. Warner.
Linking archival data to location: a case study at the
UK National Archives. Aslib Proceedings,
63(2/3):127–147, 2011.
[4] H. J. Miller. Tobler’s First Law and Spatial Analysis.
Annals of the Association of American Geographers,
94(2):284–289, 2004.
[5] K. Samp, C. Bezuit, and J. Schneider. Unifying the
Shift and Narrow Strategies in Focus + Context
Exploratory Search. In Proc. of SIGDOC 2014,
Colorado Springs, CO, USA, 2014. ACM.
[6] W. Shen, J. Wang, and J. Han. Entity Linking with a
Knowledge Base: Issues, Techniques, and Solutions.
IEEE Transactions on Knowledge and Data
Engineering, 4347(2):443–460, 2014.
[7] R. Simon, E. Barker, L. Isaksen, and
P. de Soto Cañamares. Linking early geospatial
documents, one place at a time: Annotation of
geographic documents with recogito. e-Perimetron,
10(2):49–59, 2015.
[8] I. Zandhuis, M. den Engelse, and E. Mac Gillavry.
Dutch historical toponyms in the Semantic Web. In
Proc. Workshop Population Reconstruction, 2014.
33


UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl)UvA-DARE (Digital Academic Repository)LocLinkVis: A Geographic Information Retrieval-Based System for Large-ScaleExploratory SearchOlieman, A.; Kamps, J.; Merino Claros, R.Publication date2015Document VersionFinal published versionPublished inPosters&Demos@SEMANTiCS 2015 : Posters&Demos@SEMANTiCS 2015 and DSci15WorkshopLink to publicationCitation for published version (APA):Olieman, A., Kamps, J., & Merino Claros, R. (2015). LocLinkVis: A Geographic InformationRetrieval-Based System for Large-Scale Exploratory Search. In A. Filipowska, R. Verborgh, &A. Polleres (Eds.), Posters&Demos@SEMANTiCS 2015 : Posters&Demos@SEMANTiCS2015 and DSci15 Workshop: Joint Proceedings of the Posters and Demos Track of 11thInternational Conference on Semantic Systems - SEMANTiCS2015 and 1st Workshop onData Science: Methods, Technology and Applications (DSci15), co-located with the 11thInternational Conference on Semantic Systems - SEMANTiCS2015 : Vienna, Austria,September 15-17, 2015 (pp. 30-33). (CEUR Workshop Proceedings; Vol. 1481). CEUR-WS.http://ceur-ws.org/Vol-1481/paper9.pdfGeneral rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s)and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an opencontent license (like Creative Commons).Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, pleaselet the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the materialinaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letterto: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. Youwill be contacted as soon as possible.Download date:11 Feb 2023LocLinkVis: a Geographic Information Retrieval-BasedSystem for Large-Scale Exploratory SearchAlex OliemanUniversity of Amsterdamolieman@uva.nlJaap KampsUniversity of Amsterdamkamps@uva.nlRosa Merino ClarosUniversity of Amsterdamr.merinoclaros@uva.nlABSTRACTIn this paper we present LocLinkVis (Locate-Link-Visualize);a system which supports exploratory information access toa document collection based on geo-referencing and visual-ization. It uses a gazetteer which contains representations ofplaces ranging from countries to buildings, and that is usedto recognize toponyms, disambiguate them into places, andto visualize the resulting spatial footprints.KeywordsGeographic Information Retrieval, Exploratory Search, Geo-Referencing, Interactive Visualization, OpenStreetMap1. INTRODUCTIONThe present day Web search interaction model of typing asimple keyword query and glancing over a list of 10 blue linkshas not satisfied the needs of (re)searchers who deal withlarge (thematic) collections. In the cultural heritage andlegal domains, for instance, information needs that cannotbe answered by any single document, but require comparingseveral documents or an overview of documents that satisfythe query, are quite common.One important direction for improving access to sufficientlylarge collections, such as those curated by archives and li-braries, is geo-referencing: linking information to geographi-cal location [3]. Links from documents to geospatial entitiescan be indexed by a search system, allowing users to freelyexplore the geographical aspect of the collection, or to viewthe results of a thematic query on a map. This is an impor-tant next step in making digital cultural heritage collectionsmore accessible to scholars in various branches of the hu-manities [7]. Furthermore, the most common types of inter-action that today’s users have with digital maps, pan andzoom, translate exceptionally well to existing exploratorysearch strategies: shift and narrow [5].Existing Geographic Information Retrieval (GIR) systemsdesigned for archives, however, are limited by their represen-tation of locations. These systems represent place as point(i.e. a single latitude-longitude pair) [2, 3], which uncontest-edly simplifies the technical requirements of the system, butalso limits the possibilities for the meaningful visualizationof document results. We argue that there is more to visualiz-ing a mentioned location than a single point. Qualitatively,it can make a big difference whether someone speaks abouta country, region, municipality, metropolis, highway, town,square, street, school, restaurant, or monument. How canthis difference be shown in the visualization? We proposea deceptively simple answer to this question: by displayingthe same geometry that is used to represent these locationson a map.In this paper we present LocLinkVis; a system which sup-ports exploratory information access to a document collec-tion based on geo-referencing and visualization. It uses agazetteer which contains representations of places rangingfrom countries to buildings, and which is used to recognizetoponyms, disambiguate them into places, and to visualizethe resulting spatial footprints. OpenStreetMap1 (OSM) isthe only data source that is needed to fill the gazetteer.Our current LocLinkVis prototype covers the Netherlandsand neighboring regions, but it can easily be populated byarbitrary subsets of OSM data (which has planet-wide cov-erage2). The current prototype runs comfortably on a com-modity laptop, but would benefit from more powerful hard-ware if it were to provide global coverage. For the document-side of the system our proof-of-concept focuses on existingdigital collections of parliamentary proceedings from Canada,the Netherlands, and the United Kingdom. The currentLocLinkVis prototype is limited to a Dutch gazetteer andcorpus, but will soon be expanded with the Canadian andUK corpora to match the coverage of the general Political-Mashup3 search engine.2. SYSTEM ARCHITECTUREThe systems design of LocLinkVis originates from the fol-lowing requirements. The system should efficiently:1. detect toponyms ranging from countries to buildings;2. disambiguate which geographical features the toponymsrefer to;3. build an index of documents by the locations theymention;4. use a map interface’s viewport and zoom level as queryparameters;5. visualize results on a map, at a suitable level of ab-straction.Figure 1 shows the components of the resulting system, andwhich communication occurs between them. The numbers1http://www.openstreetmap.org/2See https://tyrasd.github.io/osm-node-density/forOSM’s coverage in 20143http://search.politicalmashup.nl30Figure 1: Schematic overview of LocLinkVis’ system architecture.in this schematic indicate which requirement is satisfied in(or between) which part(s) of the system.The gazetteer builder takes OSM data as input, in theform of efficient binary dumps as well as incremental XMLupdates. Its primary purpose is to transform OSM’s nor-malized (i.e. with internal references) Node, Way, and Rela-tion instances to denormalized GeoJSON4 features. ThisJSON-based format for geospatial data structures is bet-ter suited towards retrieving and rendering spatial data,whereas OSM’s data schema favors editing it. Second, whilethe OSM data is being imported, instances of the same geo-graphical type (e.g. city or road) that share a toponym andgeometrically intersect, are merged into a single gazetteerfeature. OSM contains data at fine level of granularity, e.g.to indicate that a particular road section goes through a tun-nel. Our aim is to simplify (the side-effects of) such detailswhen they are undesirable for spatial document search.Our gazetteer, like its paper media predecessors, providesan easily searchable list of toponyms, each accompaniedby facts about its location amongst other aspects. Mod-ern gazetteers, such as the Getty Thesaurus of GeographicNames5, commonly represent the location of places as co-ordinate pairs. With thanks to the OSM contributors, wecan now provide detailed geometries for the features in ourgazetteer. Besides the data that is copied and denormalizedfrom OSM, we add to each feature the identifiers of the OSMinstances it was derived from, and build an index of featuresby all their known names (including historic toponyms).Toponym detection entails identifying which tokens froman input document refer to a place. LocLinkVis takes alexicon-based approach in which all known toponyms fromthe gazetteer are encoded into a finite state automaton bythe Aho-Corasick algorithm [1]. This allows for efficient4http://geojson.org/geojson-spec.html5http://www.getty.edu/research/tools/vocabularies/tgn/string matching between an input document and a large setof toponyms. At this stage the detected phrases are candi-date toponyms, which may or may not refer to a gazetteerfeature.NIL detection is the process by which candidate toponymsmay be identified as not-referring to any location that is rep-resented in the gazetteer. We opted for a corpus-independentapproach, which starts by counting the frequency with whichtoponyms from the gazetteer are mentioned in a Wiktionary6dump of the desired language. Wiktionary, for this purpose,serves as a compact, but high-coverage, cross section of lex-ical forms within a language. Possible toponyms that arementioned frequently, it seems safe to assume, refer eitherto well-known places or are homographs of common wordsor other names. LocLinkVis uses Support Vector Machinesthat have been trained on a small number of training ex-amples to make this distinction. Besides Wiktionary oc-currence, the feature space that is used for classification in-cludes variables obtained from SPARQL queries to DBpedia,as well as queries to the gazetteer.Location type classification takes the lexical context ofmentioned toponyms into account for disambiguation. Itcomputes for any toponym (not limited to our gazetteer)the probabilities that it refers to an instance of the typesCountry, Province, (body of) Water, Municipality, Neigh-borhood, Road, and Building. It does so on the basis of awindow of five tokens preceding and following the toponymin question. Numerical tokens are replaced by a normalizedform. The same is done for other toponyms within the to-ken window in the training examples, and for unambiguoustoponyms in unseen input. LocLinkVis offers the choice be-tween a Naive Bayes and a Maximum Entropy classifier, anduses between 25 and 85 training examples per class.Spatial analysis is useful to operationalize Tobler’s “firstlaw of geography,” that “everything is related to everything6https://www.wiktionary.org/31Figure 2: Slippy map with highlighted places that are mentioned in context of the Rotterdam harbor.Figure 3: Timeline widget showing the number of results for current Dutch government parties, with aselection of the period 1978-1987.else, but near things are more related than distant things.”[4] By taking into account the spatial distance between can-didate entities, we investigate the hypothesis that nearerfeatures are more frequently mentioned together than dis-tant features. A relatedness measure such as distance canbe used with existing methods to collectively rank candidateentities [6]. We employ a graph-based method, using ran-dom walkers to traverse a fully-connected weighted graph offeatures, to rank candidates. The next step, at the time ofwriting, is to explore how to integrate the spatial and lexicalparts of our disambiguation approach.The geo-demo user interface (UI), available athttp://geodemo.politicalmashup.nl, allows users to in-teractively validate our geo-referencing approach. Using thisUI, arbitrary text can be submitted to the geospatial webserver to view the intermediate results at each stage of thegeo-referencing process. It shows which toponyms have beendetected, which are thought not to be represented in thegazetteer, and the (detailed) output of location type clas-sification and spatial analysis for all candidate features. Aslippy map7 covers the screen, with input fields and geo-referencing details being available from an expandable menu.7http://wiki.openstreetmap.org/wiki/Slippy_MapThe search engine provides indexed access to one or moredocument collections. In our particular case these are cor-pora of national parliamentary proceedings in the rich Po-liticalMashup XML format, but plain text documents wouldalso be sufficient. In order to enrich a document with geospa-tial annotations, the text it contains is submitted to thegeospatial web server, which returns annotations of the form<Feature URI, Span, Confidence, Bounding Box>.A geospatial index ensures that the search engine can bequeried with an arbitrary bounding box, and return docu-ments from which any of the annotated locations intersectwith the bounding box. If the documents also feature a tem-poral property (e.g. creation date or period of activity), itcan enable further meaningful filtering of the results.LocLinkVis’ search UI is described in the following section.3. SEARCH UI DESIGNThe main aim of our search UI is to provide an interac-tive geospatial overview of document results. In contrastto traditional GIR systems, which have focused on associat-ing documents with a single location (often in the form ofa point), this UI displays all places that are mentioned inthe documents (see Figure 2), and with the same fidelity towhich they are rendered on the background map. To assistin searching document collections with an interesting tem-32poral aspect, we have added a timeline widget which furtherfilters the result set.The timeline widget, see Figure 3, shows the number ofplaces that are mentioned in the result set and intersectwith the map viewport. A categorical variable (i.e. facet)can be used to break the total frequency down into resultcategories. The user may make a selection on this timeline,which acts as a temporal filter within the larger query. Ad-ditionally, besides manual adjustment of the selected timeperiod, controls are provided which enable moving windowplayback which shows the dynamic of how often places werementioned through time.By these means the search UI provides a bidirectional bind-ing between the spatial and temporal aspects for the explo-ration of a search result set. When a user interacts withthe slippy map (i.e. by panning and zooming), the chart inthe timeline widget is updated to reflect the new viewport.Vice versa, when a time period is selected or adjusted, thesearch result set is (re-)filtered and the highlighted locationson the map are updated accordingly. This enables the userto seamlessly move between shift and narrow search strate-gies, as well as between the spatial and temporal dimensionsof the result space.The search UI is under active (iterative) development at thetime of writing. Hence, our prototype at http://geosearch.politicalmashup.nl will be changed periodically and maynot always be available. We are, for instance, currently ex-perimenting with the placement of result snippets in theinterface. When a user clicks a highlighted location, docu-ment results from a query could either be displayed on ornear the clicked location, or be shown within a fixed screenarea.4. CONCLUSION AND OUTLOOKIn this paper a novel GIR-based system was presented thatsupports exploratory information access to a document col-lection by means of geo-referencing and interactive visualiza-tion. LocLinkVis distinguishes itself from existing systemsthat have similar goals by working with a broader range oflocation types, and by representing a location’s geometrywith the same fidelity as to which it is rendered on Open-StreetMap. It also features a UI which allows the user toseamlessly move between the shift and narrow search strate-gies, as well as between the spatial and temporal dimensionsof the result space.This work is situated in the context of a project which aimsto improve (exploratory) information access to parliamen-tary proceedings and related cultural heritage collections.We are working towards a living lab with high-quality, reli-able prototype systems and ubiquitous interaction logging.This approach allows us to use a combination of (remote)laboratory experiments and analysis of in-the-wild usage toinvestigate how we can best assist historians, political scien-tists, journalists, and media scholars in their complex searchand sensemaking activities.Our current effort to provide accurate results for histori-cal collections mainly consists of collecting historical placenames from OSM, e.g. to compensate for spelling variantsin older texts. The gazetteer, however, does not yet containinformation about during which time period a place wasknown by a particular name, and only contains the mostrecent geometric representation that is available. This canlead to a distorted picture e.g. when borders have changedmuch, or when a monument has not always been in itspresent-day location. At least for Dutch municipalities theinformation needed to display the historical situation accu-rately is available [8], and we plan to adapt the gazetteerbuilder to incorporate it.Acknowledgements This research was supported by theNetherlands Organization for Scientific Research (ExPoSeproject, NWO CI # 314.99.108; DiLiPaD project, NWODigging into Data # 600.006.014). We would like to thankthe anonymous reviewers of this paper for their useful re-marks.5. REFERENCES[1] A. V. Aho and M. J. Corasick. Efficient stringmatching: an aid to bibliographic search.Communications of the ACM, 18:333–340, 1975.[2] L. Borin, D. Dannells, and L.-J. Olsson. Geographicvisualization of place names in Swedish literary texts.Literary and Linguistic Computing, 29(3):400–404, May2014.[3] P. Clough, J. Tang, M. M. Hall, and A. Warner.Linking archival data to location: a case study at theUK National Archives. Aslib Proceedings,63(2/3):127–147, 2011.[4] H. J. Miller. Tobler’s First Law and Spatial Analysis.Annals of the Association of American Geographers,94(2):284–289, 2004.[5] K. Samp, C. Bezuit, and J. Schneider. Unifying theShift and Narrow Strategies in Focus + ContextExploratory Search. In Proc. of SIGDOC 2014,Colorado Springs, CO, USA, 2014. ACM.[6] W. Shen, J. Wang, and J. Han. Entity Linking with aKnowledge Base: Issues, Techniques, and Solutions.IEEE Transactions on Knowledge and DataEngineering, 4347(2):443–460, 2014.[7] R. Simon, E. Barker, L. Isaksen, andP. de Soto Cañamares. Linking early geospatialdocuments, one place at a time: Annotation ofgeographic documents with recogito. e-Perimetron,10(2):49–59, 2015.[8] I. Zandhuis, M. den Engelse, and E. Mac Gillavry.Dutch historical toponyms in the Semantic Web. InProc. Workshop Population Reconstruction, 2014.33

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