=Paper= {{Paper |id=None |storemode=property |title=Interacting with the Web of Data through a Web of Inter-connected Lenses |pdfUrl=https://ceur-ws.org/Vol-937/ldow2012-paper-12.pdf |volume=Vol-937 |dblpUrl=https://dblp.org/rec/conf/www/PopovSCHS12 }} ==Interacting with the Web of Data through a Web of Inter-connected Lenses== https://ceur-ws.org/Vol-937/ldow2012-paper-12.pdf
          Interacting with the Web of Data through a Web of
                       Inter-connected Lenses
                                 ∗
                  Igor Popov                          m.c. schraefel                  Gianluca Correndo
           School of Electronics and            School of Electronics and           School of Electronics and
               Computer Science                     Computer Science                    Computer Science
           University of Southampton            University of Southampton           University of Southampton
          SO17 1BJ, Southampton, UK            SO17 1BJ, Southampton, UK           SO17 1BJ, Southampton, UK
          ip2g09@ecs.soton.ac.uk   mc@ecs.soton.ac.uk     gc3@ecs.soton.ac.uk
                            Wendy Hall           Nigel Shadbolt
                              School of Electronics and           School of Electronics and
                                  Computer Science                    Computer Science
                              University of Southampton           University of Southampton
                             SO17 1BJ, Southampton, UK           SO17 1BJ, Southampton, UK
                               wh@ecs.soton.ac.uk                 nrs@ecs.soton.ac.uk

ABSTRACT                                                         Design, Human Factors.
As a medium of structured information available on the
Web, Linked Data is still hard to access for most end users.     Keywords
Current solutions facilitating end user access to Linked Data
                                                                 End-user Interaction, Linked Data, User Interface
are either thought the use of data-mapping approaches, which
allow configureable interfaces to be quickly deployed over
pre-selected aggregations of Linked Data, or enable users        1.   INTRODUCTION
themselves to browse the Web of Data through the use of          End users engage in data-centric activities on the Web on
generic data browsers. While the first approach is useful and    a daily basis. Every time we view our news feeds on a so-
promotes surfacing and easy repurposing of structured data       cial networking site or browse shopping items on a online
it does little to promote the use of linkages to other, remote   commerce site, we are offered tools to browse, filter and find
datasets. The second approach is much less useable for end       the data we need. Much of these data-centric interactions
users, however enables them to experience browsing a inter-      and tools, however, are limiting in one fundamental way -
connected Web of Data. In this paper we present mash-            they confine us to browse and explore the only the data for
point, a framework that aims to provide a middle ground          which the tool was designed, denying the opportunity to re-
between both approaches. The approach treats data-centric        focus and find associated data on other web sites offering
applications as high-level lenses over the data, and allows      related data. One of the advocated advantages of linking
selections of data to be pivoted between applications thus       data is that links that exist between remote datasets can be
facilitating navigation. The paper presents an initial proto-    leveraged to effortlessly integrate and navigate to associated
type and discusses both implications and challenges in terms     data in remote datasets. Despite this vision, we yet to expe-
of interaction and technology.                                   rience interfaces where simple interactions allow end users
                                                                 to and navigate and find related data outside the current
Categories and Subject Descriptors                               dataset, in essence denying them to truly experience a Web
H5.2 [Information Interfaces and Presentation]: User             of Data.
Interfaces—Graphical user interfaces (GUI); H5.4 [Information
Interfaces and Presentation]: Hypertext/Hypermedia—           Currently, three approaches are adopted to surface and allow
User issues                                                   casual end users to interact with and explore Linked Data.
                                                              The first approach is the obvious one - creating a tailored
                                                              interface over pre-selected portions of Linked Data. The sec-
General Terms                                                 ond approach is a generalisation of the first - through the use
∗Corresponding author.                                        of data-mapping tools that allow developers to easily set up
                                                              and configure visually rich exploration interfaces over Linked
                                                              Data without too much programming. For example, Exhibit
                                                              [7] enables developers to create a powerful data exploration
                                                              interface without any knowledge of database technology or
                                                              programming, while mSpace [14] allows installation and con-
                                                              figuration of a scalable faceted browser over a SPARQL end-
                                                              point though an installation wizard. While both of the afore
                                                              mentioned approaches promote the use and repurposing of
Copyright is held by the author/owner(s).                     structured data, they rarely promote to users the linkages
LDOW2012, April 16, 2012, Lyon, France.                       that exist to various other datasets on the Web of Data. In
effect, once deployed they create their own data silo - use-
ful for exploring the data over which the interface acts as a               Countries                           Currency
lens, but unable to relate to data in other, remote datasets.
The third approach lets users explore and aggregate arbi-                     USA                                      USD
trary data through the use of generic data browsers, which
                                                                             Ecuador
offer browsing the Web of Data as a analogy of browsing the
Web of Documents. For example, the Tabulator [3] allows                        UK
users to browse graphs of RDF1 , specify arbitrary selections                                                          GBP
of the data and analyse the selected data through inputing
                                                                            Germany
them in a variety of widgets such as charts, maps and time-
lines. Generic data browsers consume and present the data                    Austria                                   Euro
on demand and do not require any configuration. However,
since RDF does not prescribe any representational informa-                   France
tion, generic data browsers often resort to generic represen-
tations - a one size fits all interface for data. Additionally
the interaction and navigation in a generic browser is closely                Current view                      Refocused view
associated with the underlying RDF model, which often is
too fine grained for the casual user and requires transfor-                                  Set-oreiented operation
mations or finding suitable representations before it can be
used to solve a particular information need. For such rea-
                                                                  Figure 1: Abstract representation of a set-oriented
sons, generic data browsers are often too complex for casual
                                                                  operation.
Web users - users that are used to visually rich and custom
made interfaces.
                                                                  /facet [5] already provide ways to quickly deploy interfaces
A trade off of is evident when accessing Linked Data us-
                                                                  over structured data. Most of these tools, however, offer
ing data-mapping approaches on the one hand and generic
                                                                  deploying data exploration interfaces over relatively simple
tools on the other. I the first case we sacrifice navigability
                                                                  collections of data; for example a collection of set of re-
through Linked Data as a unified, inter-connected resource
                                                                  sources (e.g. a collection of countries) and several facets
and be satisfied with islands of applications over limited data
                                                                  for which can be visualised and used for filtering. Naviga-
sources unable to interact with each other. If we use more
                                                                  tion and exploration of data from complex graphs, however,
generic solutions, however, we risk poor usability and expe-
                                                                  requires more advance interactions. Browsers such as Par-
rience will thwart large numbers of users from experiencing
                                                                  allax [6], Humboldt [9], Explorator [1] and gFacet [4] intro-
and gathering information from a integrated Web of Data.
                                                                  duce the notion of pivoting and set-oriented browsing. Set-
In this paper we present our approach to reconcile these vi-
                                                                  oriented browsing is a natural generalisation of the Web’s
sions by offering a middle ground between both approaches.
                                                                  one-to-one browsing paradigm to a many-to-many brows-
We propose a framework that allows data-centric interfaces
                                                                  ing method since manipulating data often requires dealing
to be linked based on equivalent identifiers in their respec-
                                                                  with multiple items simultaneously and common semanti-
tive data sources, enable them to express their state based
                                                                  cally typed links offer a consistent way of refocusing with
on these identifiers, and allow these identifiers to be passed
                                                                  multiple items. Figure 1 displays in abstract the concept of
as input from one application to another as a way of enabling
                                                                  set-oriented browsing. The majority of set-oriented browsers
navigation. In effect, our framework views applications as
                                                                  offer a user interface to explore and query graph data; addi-
a higher level lenses or views over graphs of data on the
                                                                  tionally browsers such as Parallax and Tabulator allow users
Web. The framework potentially unlocks novel interaction
                                                                  to select data from the explored graph and visualise the re-
possibilities and allows for citizen end users to experience an
                                                                  sults as maps, charts, timelines and calendar views.
unbounded Web of Data.

This paper is structured as follows. In the following section     2.1   Issues with Existing Approaches
we briefly discuss related work and discuss challenges facing     As we noted in the introduction, data-mapping approaches
existing approaches. In Section 3 we present mashpoint 2 , a      offer useful and usable interfaces for interacting with data
framework for using data-centric applications as lenses over      but limit the interaction to the data for which the interfaces
the Web; we discuss how users interact with multiple appli-       are intended for; generic data browsers on the other hand,
cations to explore and solve data-intensive needs. In Section     which are capable of browsing and exploring arbitrary data
4, we discuss implementation details. Section 5, discusses        from graphs, have not as yet been widely adopted. In the
the implications both from an interaction perspective and         following we offer several reasons for their low adoption.
socio-technical perspective. Finally we conclude in Section
6 and discuss future work.
                                                                  Dealing with Fine-grained Data. Often times the data
2.     RELATED WORK                                               that the data browser exposes is much too granular for end
As discussed in the introduction of this paper, a number          users, often requiring them to do complex transformations
of tools, such as Exhibit and Dido [7, 8], mSpace [13], and       or many selections before they can complete a information
                                                                  related task. For example, a simple question of viewing a
1
    http://www.w3.org/RDF/                                        visualisation of countries GDP/per capita on a map will re-
2
    http://www.mashpoint.net/                                     quire multiple steps to complete. Normally, a user would
have first to explore the graph and find resources of ”Coun-      3.   MASHPOINT: USING
tries” that will probably be associated with properties such           INTER-CONNECTED DATA-CENTRIC
as latitude, longitude, GDP and population. Then, a user
would have to find and specify which properties will be used           APPLICATIONS AS LENSES
to query. Moreover, GDP per capita might not be avail-            In this Section we describe mashpoint 4 our prototype frame-
able, so a user would have to combine the overall GDP and         work for using and navigating through higher level abstrac-
population data before the data can be used in, for exam-         tions or lenses over data. The basic premise of the mashpoint
ple, a chart visualisation widget. Eventually, the user can       framework is that when data is viewed or interacted with by
reach the desired result, however the process can be long         end users, it should always be represented within a certain
and error prone. For the majority of end users, these inter-      context. Data-centric applications are perfect examples of
actions are often too complex and time consuming. More-           data viewed in context and therefore considered as lens over
over, browsers rarely capture this transformation from data       some data in the mashpoint framework. A data-centric ap-
to usable knowledge done by users and miss the opportunity        plication is any application that is powered by and offers
of offering previous results as a suggested lens to new users     some interaction over some data. For example an Exhibit
in the browser3 .                                                 is a typical data-centric application. With mashpoint our
                                                                  goal is to enable users to select specific data through the
                                                                  interactions offered in one application and pivot (i.e. exe-
Information Overload. Even with a good exploration tool           cute a set-oriented operation with that selection) to another
that abstracts machine-readable data and allows users to          application that can accept that data as input and provide
perform various queries, graphs of data can still be diffi-       new information corresponding to the selection done in the
cult to explore. They can hold enormous amounts of data,          previous application. In such a way we achieve set-oriented
thus frequently requiring users to find and filter to a small     navigation through graph data. Figure 2 depicts this in-
                                                                  teraction technique between two mashpoint enabled appli-
portion of the dataset. Additionally, when engaged in an
exploratory search - search where users have no concrete in-      cations. In the example, the first application5 (Figure 2a)
formation goal but rather engage in exploration - they can        shows a simple data-centric application which allows users
find it difficult to figure out which properties would make       to explore data about countries GDP/per capita and pop-
sense to combine, visualise, or which properties would make       ulation information by allowing the data to be filtered by
good facets for filtering. The authors of BrowseRDF [10]          ”Income level” or ”Region”. For example, selecting ”Low
were the first to take note of this issue by trying out an au-    income” from in the first application will filter and show
tomatic way of detecting useful facets. They acknowledge,         low income countries to users. A user can then click on
however, that automatic approaches are limited and that           the mashpoint button (Figure 2b), which pops up a window
                                                                  and offers other applications that can take and offer new
additional knowledge about the ontology is required. While
in the future data-centric browsers could analyse graphs of       insights regarding the selected data in the first application.
data and offer recommended views based on established on-         For example, a user may want to view CIA factbook data
tologies we believe that such capabilities are not feasible in    about the ”Low income” countries and choses to open that
the foreseeable future.                                           application6 (Figure 2c). The CIA factbook application has
                                                                  various data about countries. For example, the user can
                                                                  view information about countries birth-rate vs. death-rate
                                                                  and filter the existing selection on different facets. Note that
Representation. Unlike the Web, where each page is care-          the items that are shown in the new application reflect the
fully crafted for human consumption, a Web of RDF data is         items chosen in the previous application.
purposely devoid of any presentational content as a adher-
ence to the principle of separation of content from presenta-     As part of the development of this framework, we started
tion. Therefore responsibility is transferred to the browser to   adapting and linking existing data-centric applications on
figure out how to represent data when the data is fetched.
                                                                  the Web. Figure 3, shows three other applications that we
Generic browsers currently only base their representations        adapted and linked up using our framework. The first one7
and browsing models on the triple data model of RDF, and          (Figure 3a) is a simple Exhibit showing images of world cur-
this is often reflected in browsers by employing generic rep-     rencies, and the currency code. The second application8
resentations, using simple heuristics to display data (e.g.
                                                                  (Figure 3b) is a simple exploration application which allows
searching for rdfs:label to display a resource), or provid-       users to view and browse countries flags depicted on a map.
ing navigation using the links only between neighbouring          The third application9 (Figure 3c) is an existing application
resources (those who share a link) in the graph. Additional       we found on the Web10 that we integrated into our frame-
representational knowledge such as lenses [11] can improve        work.
data representation, however crafting lenses without any
knowledge of the context in which they will be used in the        In the following we describe several examples how combin-
generic browser is a challenge. Moreover, it is unclear who       ing and navigating with different selections in the data can
should bear the effort of providing lenses for generic browsers
- the publisher of the data or the browser consuming the          4
                                                                     http://www.mashpoint.net
data, and what is the immediate benefit of providing repre-       5
                                                                     http://mashpoint.net/demoapps/countriesincome/index.html
sentations of the data as lenses as opposed to just building       6
                                                                     http://mashpoint.net/demoapps/birthratevsdeathrate/index.html
a custom made web site to display a publishers data.               7
                                                                     http://mashpoint.net/demoapps/currencycodes/index.html
                                                                   8
                                                                     http://mashpoint.net/demoapps/flagsonamap/index.html
3                                                                  9
  Parallax [6] allows users to export live views of the data         http://mashpoint.net/demoapps/mapmigrations/index.html
                                                                  10
and embed them in blogs and web pages.                               http://migrationsmap.net/
                     a    Select or Filter items


      Countries income per capita                                 Countries birth rate vs. death rate




                                                                                                                    c
                                                                                                        Pivot with selected items
                                                                                                         on selected application
             b

     Choose from applications
      that can take selected
          items as input



                         Figure 2: A pivoting operations between two applications in mashpoint.


produce some interesting insights into the data:                       South-east Asia.

                                                                    • Continuing from the previous example, once viewed ge-
   • In the previous example we used an application that              ographically, a user can chose to view additional data
     showed World Bank data about GDP/per capita (Fig-                about the selected ”Low income” countries by pivoting
     ure 2a). A user can browse the data in that application          to the CIA Factbook application (Figure 3b) and ex-
     using the facets that are provided, however, the appli-          plore data about birth rates and death rates for the
     cation provides only a single representation of the data.        selected, low income countries. The user decides to
     A user may wish to view countries on a map in order              compare these with high income countries so he/she
     to see how countries of different income groups are              repeats the same navigation, only this time starting
     distributed geographically (for example, which conti-            with a high income countries in the first application.
     nents contain ”Low income” countries?). Using current            The user can then conclude that there is great diver-
     tools on the Web, a user would be required to copy and           sity in both birth rates and death rates in low income
     paste each country in another application (e.g. Google           countries as opposed to high income countries where
     Maps) to answer this question. Using mashpoint, how-             death rates are fairly consistent, and birth-rates expe-
     ever, the user can take any selection of the data and            rience small variations.
     find applications that are able to provide geographic
     information and representations about the data. For            • Similarly to the previous example, a user might chose
     example, after filtering to ”Low income” countries the           to view migration patterns and instead of grouping
     user can open the mashpoint dialog and select the                countries by income levels he/she might be interested
     Flags on a map application (Figure 3a), which can dis-           in a particular geographic region. For example, piv-
     play the current selection of countries on a map as little       oting from Middle-eastern countries in (Figure 2a) to
     flag markers on a map. Immediately it is revealed that           the Map Migrations app (Figure 3c) can reveal to the
     out of the all the low income countries only a single one        user that people from those countries typically migrate
     (Haiti) is in the Americas, while the rest of the low in-        to countries in the same region and to countries of the
     come countries are in sub-saharan Africa, Central and            Western Europe and Northern America.
    a    Currency codes                                                                             b    Flags on a map




                                    c    Migrations map


                       Figure 3: Example applications linked with the mashpoint framework.


   • A user is planing a trip across Europe, traveling to mul-     4.    IMPLEMENTATION
     tiple European countries. The user is aware that some         This Section describes the implementation details of mash-
     European countries share a single currency however            point. Our investigation into designing mashpoint began
     needs information about each of the countries he/she          with the simple interaction challenge by asking ”Why are
     is traveling to. Deciding that the best way to quickly        generic data browsers unusable?” and ”How do we solve
     select the countries of interest is to use a map, the         these problems, and where can we gain in usability with-
     user selects the countries of interest on the Flags on        out sacrificing browsing and navigating capability?”. While
     a map application (Figure 3a). By selecting the Cur-          the implementation of mashpoint were guided by these prin-
     rency codes application (Figure 3b) the user is able to       ciples, we tried to implement mashpoint so that the barrier
     pivot with the current selection of countries, obtain-        for entry for linking application to the framework would be
     ing the corresponding currencies of each country. This        minimal.
     saves the user time since the alternative would be to
     look up each country and integrate the information            The implementation consists of three parts: (1) the appli-
     manually.                                                     cations themselves, which need to be data-centric in nature
                                                                   and be built with certain requirements, (2) a discovery ser-
If we examine carefully the above examples, an interesting         vice that allows applications to look up other applications
observation can be made from each example. Each applica-           so that the user can pivot between them and (3) a means
tion by itself offers very limited capabilities to interact over   of communication between the applications and discovery
that data. By enabling selections of data to be pivoted or         service. In the following we discuss each part in detail.
shifted to other applications, we not only aid in the discov-
ery of new information, which is one of the advocated uses         4.1   Applications
of Linked Data, but additionally allow users to interact with      In order to enable pivoting between applications, they need
the newly found information in a way that is tailored for the      to be designed according to some specifications and rules.
specific data to be displayed.                                     Our choice of specifications was motivated by a desire to
make the integration of new and existing data-centric ap-               a
plications as painless as possible i.e. not to impose any un-
necessary learning curves or restrict developers to use any           http://application.com/#?mashpoint=uri1
particular technology. Thus to link an application to mash-
point, it needs to have the following properties:
                                                                       b
                                                                      http://application.com/#?mashpoint=uri1,uri2

   • Offer Data-centric features. Each application in
     mashpoint needs allow interaction over data with iden-
     tifiable resources. An application can hold multiple
                                                                        c
     collections of identifiable resources - for example be
                                                                      http://application.com/#?mashpoint=uri1,uri2|uri3
     about People, Countries, Events etc. An Exhibit like
     the one in Figure 2c is a typical example of a data pow-
     ered application that offers browsing over data about
     countries. In the data of this particular Exhibit, each
     country is an identifiable real-world object.               Figure 4: Preserving the state in a mashpoint-linked
                                                                 application.
   • Use of URIs. While the data underlying the appli-
     cation does not necessarily need to be in RDF, an URI
                                                                 instantiation of mashpoint we rely on Freebase11 as a ser-
     needs to be present for each identifiable resource of the
                                                                 vice to which data used in applications need to be recon-
     data. In our examples, since the data is about coun-
                                                                 ciled. Note that we have chosen Freebase for convenience
     tries, each Country needs to be be associated with an
                                                                 reasons - Freebase and the support offered in Google Refine
     URI. The use of URIs is also needed in order to be
                                                                 offers tools to quickly reconcile12 arbitrary data with Free-
     able to save the state of the application. We discuss
                                                                 base concepts. While the data in the applications need to
     how to preserve the applications state in the next two
                                                                 be reconciled against Freebase, it does not preclude using
     points.
                                                                 other data sources that already use established URIs. For
                                                                 example applications consuming Open Linked Data can use
   • Be able to select multiple resources. An applica-
                                                                 resources such as sameas.org13 to either reconcile their data
     tion in this framework should typically enable selection
                                                                 to Freebase or even use the service in real time (although
     of resources in order to be able to pivot with arbitrary
                                                                 the former is probably the preferred solution because of op-
     selections of data. Selections of the data can can be
                                                                 timisation issues). In essence, it does not particularly mat-
     provided in multiple ways. For example, items can be
                                                                 ter which URIs we offer as reconciliation, since the frame-
     selected thought filtering by providing various facets
                                                                 work requires just reconciliation of identifiers. Moreover,
     over the data and/or allow arbitrary items to be se-
                                                                 the architecture could also be redesigned in a different way
     lected. This selection of items will then be passed on
                                                                 - it could allow applications to use whatever URIs they see
     as input to another application. Whenever an appli-
                                                                 fit and try to reconcile them and do discovery in real time
     cation changes its focus, the state of the application
                                                                 through the use services such as sameAs.org. To illustrate
     should be made explicit in the URL of the application.
                                                                 this we have already connected Visor14 [12] a end-user tool
     In mashpoint we require each application to list the
                                                                 for exploring DBPedia [2] data to the mashpoint framework.
     current resources in view through a mashpoint param-
                                                                 At this point of time, however, a priori reconciliation pro-
     eter in the URL. Figure 4 depicts the saving of state
                                                                 vides a more optimised solution to the co-reference problem
     in each application. Figure 4a for example depicts an
                                                                 in our case.
     application showing a single resource and a mashpoint
     that denotes this state. Similarly, Figure 4b shows the
     interface on a state with two resources. The state can      4.2         Discovery Service
     also group a list of resources (Figure 4c) in order to      In order to be able to find applications which can be used to
     reflect certain collections of resources e.g. a interface   pivot from the current application we implemented a discov-
     that displays data about both ”Countries” and ”Cur-         ery service for mashpoint-enabled applications. The discov-
     rencies”.                                                   ery service is a repository that simply keeps a record about
                                                                 which URI identifiers can be represented in which applica-
   • Be able to represent multiple resources on in-              tions. Applications therefore need to register themselves in
     put. Application should be able to take any arbi-           the discovery service and ”subscribe” their URI identifiers.
     trary selection of URL identifiers that represent the       Registering with a set of URIs means that an application
     resources of the application and be able to show some       can represent and show data about any subset of the iden-
     representation of that data that reflects the selected      tifiers it is subscribed to. Once registered, each application
     items i.e. be able to arbitrarily retrieve any state of     can communicate with the discovery service to find other
     the application.                                            applications that can take the current selection (represented
                                                                 through the URIs in its state) as input. Figure 5 depicts
                                                                 11
                                                                    http://www.freebase.com
The choice of URIs is also an important factor in the cur-       12
                                                                    http://code.google.com/p/google-
rent implementation of the framework. In order to enable          refine/wiki/ReconciliationServiceApi
                                                                 13
pivoting between applications we need identical identifiers         http://sameas.org/
                                                                 14
across all mashpoint enabled applications. In our current           http://visor.psi.enakting.org/
this architecture. For clarity, URI identifiers are represented   an application may want to offer users pivoting to only a
with dots, squares and triangles to denote different groups of    certain, predefined set of applications. Therefore the pub-
URIs found across different applications. For example Ap-         lisher of the application can discover those applications once,
plication 1 is registered with the dot identifiers which means    and include them as regular links in the application. This
it can take any subset of these identifiers as input. Applica-    removes the need for a third party discovery service, how-
tion 2 can either take the any subset of dot identifiers but it   ever it is now up to the publisher to keep the links to the
can also take any subset of square identifiers as input. Sim-     other applications consistent with the current state of the
ilarly Application 3 can take subsets of square and triangle      application.
identifiers. These groups of URI identifiers are assigned by
the application registering to the discovery service.             5.    DISCUSSION
                                                                  In this Section we discuss open issues, challenges and impli-
                                                                  cations in adopting mashpoint as a framework.

                              Discovery service                   5.1    Interaction Challenges
                                                                  A number of interaction challenges need to be investigated
                                          App 2                   and addressed in order to mitigate any usability issues. First,
                              App 1
                                                                  unlike a generic browser where data is viewed, browsed and
                                                                  manipulated within the context of a single application, mash-
                                                  App 3           point proposes an approach to data browsing where views of
        1
                                                                  the data are provided by distributed applications that can be
 Send URIs in                                                     contributed by many publishers. Evaluating how well users
                                   Recieve apps that              can combine and pivot data between different applications
 current view                                                 2
                                  can represent URIs              in order to solve data-centric tasks remains to be explored
                                                                  and evaluated.

                                                                  Another issue is the implementation of the set-oriented op-
                                                                  erations in mashpoint. In the current implementation, when
                                                                  the discovery service is queried with a set of URIs, every ap-
                                                                  plication that can represent some subset of these URIs is
                                                                  retrieved. For example, if an applications state is currently
                 App 1                App 2               App 3   focused on three countries e.g. France, Germany, and Brazil,
                                                                  and another application can show data only about European
                                                                  countries, that application will also be retrieved when ap-
                                                                  plications will be requested for those three countries, even
                                                                  though it will only be able to show information on two out
                                                                  of the three countries. This means that in some cases not
                          3    Pivot to other apps                all URIs will be able to be represented in the application to
                                                                  which the user will pivot. Such information needs to be sur-
                                                                  faced to the user, or ideally, enable users to filter and browse
Figure 5: Architecture of the mashpoint framework.                particular types of applications according to the content or
                                                                  size of the subset they can take as input.
4.3    Pivoting Across Applications
In order to enable pivoting across applications, they need to     Another problem that might hinder usability is the lack
communicate and request information based on the current          of context between pivoting steps in applications. Some-
state of the application. Each application therefore commu-       times the data in two linked applications will follow a one-
nicates its state to the discovery service i.e. it sends the      to-one mapping e.g. two applications both showing data
URIs that currently represent the data which is viewed in         about countries. This corresponds as navigation through
the application, and retrieves back a list of applications that   resources that are linked through a owl:sameas relation. As
are able to receive those URIs as input.                          we’ve seen in our examples, however, pivoting can take place
                                                                  between applications that contain data on diverse topics,
In order to facilitate this communication, each application       for example pivoting from an application about ”Countries”
in mashpoint incorporates a small JavaScript widget that          to an application about ”Currencies”. This corresponds to
is able to parse the URL for the URI identifiers and send         navigating through resources with arbitrary links between
them to the mashpoint discovery service (Figure 5-1) The          them and often times the relationships between them will
discovery service then retrieves which applications can take      be many-to-many. In our example, the application show-
the URIs as input and sends them as a response with their         ing currency data might not explicitly state which countries
states reflecting the identifiers in the request (Figure 5-2).    are using that currency. Thus a user would find it difficult
The widget in each application is a third party code that         figuring out which country shown in the first application
adds a mashpoint button, facilities the communication with        corresponds to which currency in the second one. Several
the discovery service and pops up the dialog that suggests        solutions to this problem are possible. First, either publish-
appropriate applications to users. We note that the discov-       ing practices will compound users to normally include labels
ery mechanism and widget may be omitted from an appli-            or representations of the items of input, or second, the state
cation. For example, cases may exist where a publisher of         of an application encoded in the URL can include additional
contextual information that will be sent alongside the URIs.                          is useful by itself. As a publishing recommendation mash-
At present, however, this remains future work.                                        point acts in a very similar way. Applications can be viewed
                                                                                      as contributions which are useful by themselves - they allow
                                                                                      some value over the data they were initially designed for. By
5.2    Social Contribution Factor                                                     linking them up, and enabling pivoting to other data-centric
                                                                                      applications, the original application can only increase the
                                                                                      value of the original application. In fact, this attribute may
                                                                                      provide incentive for publishers of data-centric applications
                                                                                      on the Web to link their data using frameworks such as
                                                                                      mashpoint.


                                              Application 2
                                                                                      5.3   Low Barrier for Entry
                                                                                      Although none of the applications we have presented in this
                      Application 3                                                   paper directly operates over live Linked Data, or directly
                                                                                      use RDF data directly (although we extracted some of the
                                                                         Area size    data from Linked Data sources), we believe this fact to be
                 Image_file                                                           an added strength to the framework, since it only lowers the
                                                                                      barrier for linking new applications - it does not mandate or
                                                                         Population
                                                                                      impose any particular data model on the user. This is not
                                                              areaSize
      Currency
                    image                                                             to say that the applications using this framework cannot
       code
                                                                            GDP       use standard data-models such as RDF. In fact, as the title
                                                           popSize
          currency code                                                               our our paper suggests, we view the applications as high-
                                                           hasGDP
                                                                                      level lenses over graphs of data, as depicted in Figure 6.
                     Currency                  Countries
                                                                                      In Figure 6 we can see the connections between the data
                                hasCurrency                                           items used by the mashpoint-enabled applications earlier.
                                                           birthRate                  The applications encapsulate views over the data, and the
                                                           deathRate     Birth Rate
                                                                                      relationships between the data are just hidden within the
                                                                                      individual applications. Thus applications are can chose to
                                                                                      use either RDF or any other data model and pivoting takes
                                                                            Death
                                                                                      place where these lenses overlap.
                                                                            Rate



                                        Application 1
                                                                                      5.4   Incentives for Publishing and Linking
                                                                                      During the last 2 years, the Linked Data community has
                                                                                      been advocating data publishing using Linked Data stan-
                                                                                      dards, and has promoted the use of these standards as a
                                                                                      quality indicator for data available on the Web15 . However,
                                                                                      the benefits of publishing Linked Data and linking to other
                                                                                      remote data sources remain elusive for most data publishers
                                                                                      and consumers outside the community. Often the results
                                                                                      are data repositories that are rarely used and provide sparse
Figure 6: Model of data and it’s relationships en-                                    linkages to other remote datasets. This lack of immediate
capsualted .                                                                          value for the effort of converting ones data as Linked Data
                                                                                      can thwart many potential adopters of these technologies.
                                                                                      With mashpoint we hope to target this problem, particularly
By design, mashpoint sets forward a paradigm that has in-                             in providing incentives for linking data. As we already men-
herently a social factor of contribution, which is similar to                         tioned, publishers of data-centric applications would only
the social nature of publishing and linking in the original                           increase the value of their applications by allowing users to
Web. The reason why applying data mapping tools such as                               find useful, related data without changing the original ap-
Exhibit [7] have seen much wider acceptance than generic                              plication. By requiring publishers to reconcile their data
browsers such as Tabulator [3] is because a publisher of an                           we already promote the use of URIs in their datasets, while
Exhibit [7] can control the look and feel of the data and im-                         showing the immediate benefit of being able to pivot and
mediately see value of providing a rich data-centric interface                        suggest related data to the users of the application.
over data. The original Web followed a similar pattern; a
published Web site offered a custom made document and a
presence on the Web - linking to other web sites only im-
                                                                                      6.    CONCLUSION
proved the quality of the web site by providing connivence of                         In this paper we presented mashpoint, a framework which
finding relating information. For example a web page about                            aims to promote the value of a Web of Linked Data by en-
events in Southampton is by itself a useful contribution to                           abling interactions that take advantage of links between re-
the Web, and the publisher can increase the value of informa-                         mote datasets while remaining usable and familiar as brows-
tion by providing links to other pages (e.g. the Wikipedia                            ing the Web itself. As a publishing framework, we view
page for Southampton or other related web pages offering                              mashpoint as an extension to the current landscape of tools
events information about Southampton). However it is im-                              15
                                                                                       http://inkdroid.org/journal/2010/06/04/the-5-stars-of-
portant to note that even without the links, the web site                             open-linked-data/
providing end user access access to the Web of Data (Figure                                    2010), volume 6088 of LNCS, pages 288–302,
7). While we’ve communicated the overall idea of having                                        Berlin/Heidelberg, 2010. Springer.
data-centric applications serve as lenses over Linked Data,                                [5] M. Hildebrand, J. van Ossenbruggen, and
the work presented here is still work in progress and many                                     L. Hardman. /facet: A browser for heterogeneous
open challenges remain. Our future work include evaluating                                     semantic web repositories. In International Semantic
the initial prototype with users allowing them to complete                                     Web Conference, pages 272–285, 2006.
data-intensive task by navigating thorough a Web of tens                                   [6] D. Huynh and D. Karger. Parallax and Companion:
of mashpoint-linked applications. We believe that the study                                    Set-based Browsing for the Data Web. 2009.
will provide many insights into the overall design and im-                                 [7] D. F. Huynh, D. R. Karger, and R. C. Miller. Exhibit:
plementation of the framework. If mashpoint achieves wide                                      lightweight structured data publishing. In WWW ’07:
adoption, our long term plan will be to study the ecology of                                   Proceedings of the 16th international conference on
inter-linked applications it will create.                                                      World Wide Web, pages 737–746, New York, NY,
                                                                                               USA, 2007. ACM.
                        Configureable Simple,                                              [8] D. R. Karger, S. Ostler, and R. Lee. The web page as
                        Data Exploration Tools                                                 a wysiwyg end-user customizable database-backed
                     (Exhibit, mSpace, \facet etc.)
                                                                                               information management application. In UIST ’09,
 Usability




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7.           ACKNOWLEDGMENTS                                                                   C. Harris, and M. Wilson. The evolving mspace
This work was supported by the EnAKTing project, funded                                        platform: leveraging the semantic web on the trail of
by EPSRC project number EI/G008493/1. Many thanks                                              the memex. In HYPERTEXT ’05: Proceedings of the
to Manuel Salvadores for providing useful feedback for this                                    sixteenth ACM conference on Hypertext and
work.                                                                                          hypermedia, pages 174–183, New York, NY, USA,
                                                                                               2005. ACM.
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