=Paper= {{Paper |id=Vol-1824/mepdaw_paper_6 |storemode=property |title=Temporal Evolution of Entity Relatedness using Wikipedia and DBpedia |pdfUrl=https://ceur-ws.org/Vol-1824/mepdaw_paper_6.pdf |volume=Vol-1824 |authors=Narumol Prangnawarat,Conor Hayes |dblpUrl=https://dblp.org/rec/conf/esws/PrangnawaratH17 }} ==Temporal Evolution of Entity Relatedness using Wikipedia and DBpedia== https://ceur-ws.org/Vol-1824/mepdaw_paper_6.pdf
Temporal Evolution of Entity Relatedness using
          Wikipedia and DBpedia

                    Narumol Prangnawarat and Conor Hayes

      Insight Centre for Data Analytics, National University of Ireland, Galway
            {narumol.prangnawarat,conor.hayes}@insight-centre.org



       Abstract. Entity relatedness is a task that is required in many appli-
       cations such as entity disambiguation and clustering. Although there are
       many works on entity relatedness, most of them do not consider temporal
       aspects and thus, it is unclear how entity relatedness changes over time.
       This paper attempts to address this gap by showing how entity related-
       ness develops over time with graph-based approaches using Wikipedia
       and DBpedia as well as how transient links and stable links, by which
       is meant links that do not persist over different times and links that
       persist over time respectively, affect the relatedness of the entities. We
       show that different versions of the knowledge base at different times give
       different accuracy on the KORE dataset, and show how using multiple
       versions of the knowledge base through time can increase the accuracy
       of entity relatedness over a version of the knowledge graph from a single
       time point.


1     Introduction

Many researches have made use of Wikipedia and DBpedia for relatedness and
similarity tasks. However, most approaches use only the current information
but not temporal information. For example, the entities Mobile and Camera
may have been less related in the past but may be more related at present.
This work shows how semantic relatedness develops over time using graph-based
approaches over the Wikipedia network as well as how transient links, links that
do not persist over different times, and stable links, links that persist over time,
affect the relatedness of the entities.
    We hypothesise that using graph-based approaches on the Wikipedia network
provides higher accuracy in term of relatedness score to the ground truth data
in comparison to text-based approaches. We take each Wikipedia article as an
entity, for example, the article on Semantic similarity 1 corresponds to the entity
Semantic similarity. Although the term article and entity may be referred to
interchangeably in this work, article refers to Wikipedia article and entity refers
to a single concept in the semantic network. Wikipedia users provide Wikipedia
page links within articles, so we can make use of the provided links as entities. We
assume that entities which are closely related to an entity, a Wikipedia article in
1
    https://en.wikipedia.org/wiki/Semantic_similarity
this case, are mentioned in that Wikipedia article. Hence, closely related entities
share the same adjacent nodes in the Wikipedia article link network. We make
use of the temporal Wikipedia article link network to demonstrate the evolution
of entity relatedness and how transient or stable links affect the relatedness of
the entities. We analyse different models of aggregated graphs, which integrate
networks at various times into the same graph as well as time-varying graphs
which are the series of the networks at each time step.
    We first show that the proposed graph-based approach outperforms the text-
based approach in terms of the accuracy of relatedness score. Then, we present
our proposed similarity method, which outperforms the baseline graph-based
similarity methods in term of relatedness score accuracy over various different
network models. We also show the evolution of relatedness as well as how tran-
sient links and stable links effect the relatedness using graph-based similarity.


2     Related Works
2.1   Semantic Relatedness
Semantic relatedness works have been carried out for words (natural language
texts such as common nouns and verbs) and entities (concepts in semantic net-
works such as companies, people and places). The approaches used for semantic
relatedness includes corpus-based or text-based approaches as well as structure-
based or graph-based approaches. Wikipedia and DBpedia have been widely
used as resources to find semantic relatedness. However, most approaches use
only the current information without temporal aspects. One of the well known
system is WikiRelated [13] introduced by Strube and Ponzetto. WikiRelated
use the structure of Wikipedia links and categories to compute the relatedness
between concepts.
    Gabrilovich and Markovitch proposed Explicit Semantic Analysis (ESA) [5]
to compute semantic relatedness of natural language texts using high-dimensional
vectors of concepts derived from Wikipedia. DiSER [1], presented by Aggarwal
and Buitelaar, improves ESA by using annotated entities in Wikipedia.
    Leal et al. [9] proposed a novel approach for computing semantic relatedness
as a measure of proximity using paths on DBpedia graph. Hulpus et al. [8]
provided a path-based semantic relatedness using DBpedia and Freebase as well
as presenting the use in word and entity disambiguation.
    Radinsky et al. proposed a new semantic relatedness model, Temporal Se-
mantic Analysis (TSA) [12]. TSA computes relatedness between concepts by
analysing the time series between words and find the correlation over time. Al-
though this work make use of the temporal aspect to find relatedness between
words, it does not show how the relatedness evolve over time.

2.2   Time-aware Wikipedia
There have been a number of works in the area of time-aware Wikipedia anal-
ysis. The authors have primarily focused on content and statistical analysis.
WikiChanges [10] presents a Wikipedia article’s revision timeline in real time as
a web application. The application presents the number of article edits over time
in day and month granularity. The authors also provide the extension script for
embedding a revision activity to Wikipedia. Ceroni et. al. [4] introduced a tempo-
ral aspect for capturing entity evolution in Wikipedia. They provided time-based
framework for temporal information retrieval in Wikipedia as well as statistical
analysis such as the number of daily edits, Wikipedia pages having edits and top
Wikipedia pages that has been changed over time. Whiting et. al. [15] presented
Wikipedia temporal characteristics, such as topic coverage, time expressions,
temporal links, page edit frequency and page views, to find how the knowledge
can be exploited in time-aware research. However, in-degree and out-degree are
the only networks properties that are discussed in the paper.
    Recent research from Bairi et. al. [2] presents statistics of categories and
articles, such as the number of articles, the number of links and the number
of categories, comparing between the Wikipedia instance in October 2012 and
the Wikipedia instance in June 2014. The authors also analysed the Wikipedia
category hierarchy as a graph and provided statistics of the category graph such
as number of cycles and and the cycle length of the two Wikipedia instances.
Contropedia [3] identifies when and which topics have been most controversial
in Wikipedia article using Wikipedia links as the representation of the topics.
However, the approach also focus on the content changed in the article.

 Our work make use of the changes in Wikipedia to analyse evolution of entity
relatedness. We show how entity relatedness develops over time using graph
based approaches over Wikipedia network as well as how transient links and
stable links affect the relatedness of the entities.


3     Dataset
The Wikipedia data can be downloaded from the Wikimedia download page2 ,
where dumps are extracted twice a month. A major limitation of data availability
from Wikipedia dumps is that the oldest available Wikipedia dump at the time
of our experiment was from 20 August 2016.
    We treat each Wikipedia article as an entity. Each Wikipedia article has user
provided Wikipedia article links which link to the corresponding Wikipedia arti-
cles. We extract Wikipedia links within Wikipedia articles from each Wikipedia
dump. Figure 1 shows an example of a part of Wikipedia article link network
of the DBpedia article3 . The part of DBpedia article contains links to Database,
Structured content, Wikipedia, World Wide Web, Semantic Query, Tim Berners-
Lee, Dataset, and Linked Data. The article links of all articles in Wikipedia con-
struct the full Wikipedia article link network.
    As the oldest Wikipedia dumps available for download on Wikimedia Down-
loads page is Wikipedia dump on 20 August 2016 at the time we conduct this
2
    https://dumps.wikimedia.org/
3
    https://en.wikipedia.org/wiki/DBpedia
Fig. 1: An example of a part of Wikipedia article link network or the DBpedia
article



experiment, in order to get older Wikipedia link data, we obtained data from
DBpedia4 which is an open knowledge base extracted from Wikipedia and other
Wikimedia projects. We use the page links datasets which are the relation-
ship of article links within each article, the same information as the Wikipedia
links we extracted from Wikipedia. Each DBpedia concept corresponds to a
Wikipedia article. For example, the DBpedia concept http://dbpedia.org/
resource/Semantic_similarity corresponds to the article Semantic similar-
ity 5 . We refer to both the Semantic similarity article and the DBpedia concept
http://dbpedia.org/resource/Semantic_similarity as the entity Seman-
tic similarity. We make use of page links dataset from DBpedia to construct a
series of Wikipedia article link networks for each year from 2007 to 2016. The
DBpedia versions used are shown in Table 1.


4     Methodology

We take each Wikipedia article as an entity. We assume that entities which are
closely related to an entity, a Wikipedia article in this case, are mentioned in that
Wikipedia article. Hence, closely related entities share the same adjacent nodes
in the Wikipedia article link network. However, there might be some articles that
link to a lot of the articles that might not be semantically related. For example,
the main page, which is the landing page for featured articles and news, is not
semantically related to the articles it links to. On the other hand, articles that
do not have many links to other pages might have more semantically relation
to their links. Because of this reason, we apply weights to the relationships to
penalise the articles that link to many other unrelated articles.
4
    http://wiki.dbpedia.org
5
    https://en.wikipedia.org/wiki/Semantic_similarity
                             Table 1: DBpedia versions
                 Dataset      DBpedia version Wikipedia Dumps
                 DBpedia 2016 DBpedia 2016-04 Mar-2016/Apr-2016
                 DBpedia 2015 DBpedia 2015-04 Feb-2015/Mar-2015
                 DBpedia 2014 DBpedia 2014    02-May-2014
                 DBpedia 2013 DBpedia 3.9     03-Apr-2013
                 DBpedia 2012 DBpedia 3.8     01-Jun-2012
                 DBpedia 2011 DBpedia 3.7     22-Jul-2011
                 DBpedia 2010 DBpedia 3.6     11-Oct-2010
                 DBpedia 2009 DBpedia 3.4     20-Sep-2009
                 DBpedia 2008 DBpedia 3.2     08-Oct-2008
                 DBpedia 2007 DBpedia 3.0rc   23-Oct-2007



    First, we introduce different models we used to represent Wikipedia article
link networks. Then, we explain our approach we used to find relatedness over
the proposed models.

4.1   Models
To reflect how relatedness changes over time, we represent temporal information
from Wikipedia article link networks in two different ways. One is as time-
varying graphs which are a series of Wikipedia article link snapshots at each time
step. We use each version of datasets to construct a network as each snapshot.
Another is as an aggregated graph, which aggregates all networks at each time
step together with time information as weights.

Time-Varying Graphs Given an article a for a corresponding entity, the series
of networks GaS at the set of time T = {1, .., n} is constructed as a set of time
step graphs {Ga1 , Ga2 , ..., Gan }. Each graph Gat = (Vta , Eta ) represents a snapshot
of the 2-hop ego network of the article links around an entity a at the time t,
where Vta is a set of nodes where each node represents a Wikipedia entities that
have links with a or have links with the nodes that are adjacent to a at time t and
Eta is a set of edges where each edge eijt is an internal link between Wikipedia
entities i and j at time t. In other words, v ∈ Vta if at time t, eavt ∈ Eta or
eabt ∈ Eta ∧ ebvt ∈ Eta . Figure 2 demonstrate the example of a 2-hop ego network
around the entity a at time t. We construct a series of 2-hop ego networks of
Wikipedia article links over time around each seed entity that we are interested
in.

Aggregated Graphs We create different models of aggregated graphs as fol-
lows.

Intersection model
Given a Wikipedia article a for a corresponding entity, GaI = (VIa , EIa ), VIa is a
   Fig. 2: An example of a 2-hop ego networks around the entity a at time t



set of nodes where each node represents a Wikipedia article that have links with
a or have links with the nodes that are adjacent to a at all time points and EIa is
a set of edges where each edge eij is an internal link between Wikipedia entities
i and j which appear at all time. In other words, v ∈ VIa if v ∈ V1a ∩ V2a ∩ ... ∩ Vna
and eij ∈ EIa if e ∈ E1a ∩ E2a ∩ ... ∩ Ena for [1..n] ∈ T .

Union model
Given a Wikipedia article a for a corresponding entity, GaU = (VUa , EUa ), VUa a set
of nodes where each node represents a Wikipedia article that have links with a
or have links with the nodes that are adjacent to a at any time in T and EUa is
a set of edges where each edge eij is an internal link between Wikipedia entities
i and j. In other words, v ∈ VUa if v ∈ V1a ∪ V2a ∪ ... ∪ Vna and eij ∈ EUa if
eij ∈ E1a ∪ E2a ∪ ... ∪ Ena for [1..n] ∈ T .

4.2   Proposed Extended Jaccard Similarity
Jaccard similarity coefficient measures similarity between two objects using bi-
nary attributes. Given object a and b with a vector of features A and B re-
spectively, Jaccard similarity coefficient of a and b, J(a, b) is computed as the
following equation.

                                             |A ∩ B|
                                 J(a, b) =
                                             |A ∪ B|
    Taking adjacent nodes of an entity a in the Wikipedia article link network
as the features of the entity a, Jaccard similarity coefficient can reflect our as-
sumption that closely related entities share the same adjacent links in Wikipedia
article links network. However, Jaccard similarity coefficient cannot take into ac-
count non-binary features. As we discussed before, there might be some article
that links to a lot of the pages that might not be semantically related so we
want to apply weights to the relationships to penalise pages that link to many
unrelated pages. PageRank [11] is used to rank the importance of nodes. It was
originally created to rank web pages in World Wide Web network in Google
search engine. We use the same idea to apply to our Wikipedia article link net-
work. An article that mentions a lot of other articles may not be semantically
related to the articles that they link to. On the other hand, an article that is
mentioned in a lot of articles may just be a general article that is not semanti-
cally related to them. We make use of Tanimoto similarity [14] to extend Jaccard
similarity using reciprocal PageRank, which is 1 divided by PageRank score, as
weights to find similarity between each entity in the network. The underlying
assumption is that articles with lower PageRank scores might have more seman-
tically relation to their links as they only link to fewer articles that are really
related to them. Given A is a vector of reciprocal PageRank score of the articles
having links with an entity a in the 2-hop ego network around an entity a and
B is a vector of reciprocal PageRank score of the articles having links with an
entity b in the 2-hop ego network around an entity b, the relatedness between
two entities a and b is computed as:
                                            A·B
                          R(a, b) =     2       2
                                      |A| + |B| − A · B
  We apply the extended Jaccard similarity with reciprocal PageRank to our
models, time-varying graphs and aggregated graphs.


5     Experiment Results
We conducted experiments and evaluated with the KORE [6] dataset. The
KORE dataset has been created to measure relatedness between named enti-
ties. It consists of 420 related entity pairs from a selected set of 21 seed entities
from the YAGO2 [7] knowledge base from 4 different domains, which are 5 en-
tities from IT companies, 5 entities from Hollywood celebrities, 5 entities from
video games, 5 entities from television series, and one singleton entity. Each of
the entities has 20 ranked related entities. All entities in the KORE dataset
corresponds to entities in our Wikipedia article link networks. We use Spear-
man Correlation to compare the relatedness scores from each approach with the
scores from the KORE dataset. As the KORE dataset provides only the ranking
but not the score, we assume that the highest entity has a score of 20 and each
subsequent entity has a score 1 lower.

5.1   Proposed Extended Jaccard Similarity results
For each DBpedia version stated above, we constructed the series of networks of
entities seeding the entities from the KORE dataset as described in Section 4.1.
    The experiments were conducted to compare two different perspectives. In
the first evaluation perspective, we performed experiments to show that the pro-
posed graph-based approach outperforms the text-based approach in terms of
the relatedness scores. We used Term Frequency-Inverse Document Frequency
(TF-IDF) based similarity as the text-base baseline to compared to the proposed
extended Jaccard similarity. In the second evaluation perspective, we performed
experiments to show that our proposed link-based extended Jaccard similar-
ity with Reciprocal PageRank outperforms the baseline approaches in terms of
the relatedness score accuracy. We used Jaccard similarity as the baseline for
the graph-based approach to compare to our extended Jaccard similarity. We
analysed variations of features for Jaccard methods by considering only direct
predecessors of the nodes which are the entities that have links to the nodes,
only direct successors of the nodes which are the entities that have links from
the nodes, and both direct predecessors and direct successors of the nodes which
are entities that have links to or from the nodes.
    We performed TF-IDF based similarity on three different Wikipedia text
revisions. One is the revision at the time when YAGO2 was created (17-Aug-
2010) which is used to constructed the KORE dataset. The second one is the
revision at the dump time of DBpedia 2009 dataset (20-Sep-2009) and the last
one is the revision at the dump time of DBpedia 2010 dataset (11-Oct-2010).
We performed Spearman Correlation to evaluate with the gold standard dataset,
the KORE dataset, as described previously. The Spearman Correlations of the
3 different datasets compared to the KORE gold standard are shown in Table 2.
We can see that the result of the data acquired at the time when YAGO2 was
created has the highest correlation as the same information is captured at that
time.



Table 2: Spearman Correlations to the KORE gold standard with the text-based
approach for different Wikipedia dumps
          Version                                      Correlation
          Wikipedia at the time when YAGO2 was created 0.503212
          Wikipedia at Dbpedia 2009 version dump time 0.491440
          Wikipedia at Dbpedia 2010 version dump time 0.502987




    We compared the text-based approach over each version of dataset to the
graph-based approaches. In this section, we focused on DBpedia 2009 dataset
and DBpedia 2010 dataset as they are the closest snapshots to the Wikipedia
dump from 2010-08-17 which is used to constructed YAGO2 using by the KORE
dataset. We found that the graph-based approaches outperform the result from
the text-based approach in term of accuracy of relatedness score as shown in Ta-
ble 3. The Spearman Correlation to the KORE dataset from our Extended Jac-
card with Reciprocal PageRank is statistically significantly better than TF-IDF
based similarity (p-value < 0.05) on both datasets. Moreover, the results show
that our proposed extended Jaccard with reciprocal PageRank gives a better
accuracy of relatedness score than the baseline Jaccard methods. The Spearman
Correlation to the KORE dataset from our Extended Jaccard with Reciprocal
PageRank is statistically significantly better than the baseline Jaccard methods
(p-value < 0.05) on DBpedia 2009.



Table 3: Spearman Correlations to the KORE gold standard comparing text-
based approach with graph-based approaches of data from 2009 and 2010
Method/Dataset                                           DBpedia 2009 DBpedia 2010
TF-IDF                                                   0.491440     0.502987
Jaccard (direct predecessors)                            0.568509     0.568026
Jaccard (direct successors)                              0.511564     0.559898
Jaccard (both direct predecessors and direct successors) 0.578706     0.585535
Extended Jaccard with Reciprocal PageRank                0.604112     0.599284




5.2   Evolution of Relatedness

We analysed the change of correlations to the KORE gold standard in different
datasets to demonstrate how relatedness progress over subsequent years. We
found that the dataset from the network in 2009 and 2010 got the highest results.
This is because the KORE dataset is constructed using YAGO2 that use the
Wikipedia dump from 2010-08-17 [7], which is in between DBpedia version 2009
(2009-09-20) and 2010 (2010-10-11). Figure 3 shows the comparison of Spearman
Correlation result of different methods from each dataset.




Fig. 3: The comparison of Spearman Correlations to the KORE gold standard
of different graph-based methods from each DBpedia dataset
Fig. 4: Evolution of relatedness between Facebook and The Social Network in
comparison to Facebook and Justin Timberlake




    We can see from the result that the most updated knowledge bases will not
give the highest correlation if the ground truth data is created in different time.
This is because the relatedness score varies according to the relatedness of the
entities at that time. For instance, Facebook and Justin Timberlake has a higher
relatedness score in 2010 as Justin Timberlake stared in The Social Network
movie, the film portrays the founding of Facebook, and the score faded after
that as shown in Figure 4.




Fig. 5: Evolution of relatedness between Leonardo DiCaprio and Barack Obama




    As shown in Figure 5, Leonardo DiCaprio became related to Barack Obama
after 2008 as he supported Barack Obama’s presidential campaign in the 2008
election and became more related again after 2012 as his support to Obama’s
2012 campaign6,7 . As the events occurred the end of the years, the changes in
relatedness are not shown in these versions (2008 and 2012) but appear in the
next versions (2009 and 2013) instead.
    We also did a qualitative analysis for the entities which are not in the KORE
dataset as they become more related to the seed entities after the dataset was
created. For instance, Tim Cook started to have high relatedness with Apple Inc.
since 2011 when he become the CEO of the company. Figure 6 shows the relat-
edness of Apple Inc. and Tim Cook in comparison to Apple Inc. and Steve Jobs.




Fig. 6: Evolution of relatedness between Apple Inc. and Tim Cook in comparison
to Apple Inc. and Steve Jobs




Fig. 7: Evolution of relatedness between Jennifer Aniston and Justin Theroux
in comparison to Jennifer Aniston and Brad Pitt


6
    https://en.wikipedia.org/wiki/Leonardo_DiCaprio
7
    http://www.hollywoodreporter.com/news/julianne-moore-leonardo-
    dicaprio-obama-video-375796
    Another example is the relatedness between Jennifer Aniston and Justin -
Theroux 8 which became higher from 2011 when they started dating9 . While the
relatedness between Jennifer Aniston and Brad Pitt stayed high for a while after
they divorced in 200510 and then faded as shown in Figure 7.
    We performed the Spearman Correlation between different datasets and found
that the correlations of the entity relatedness are higher to the dataset versions
that are closer in time to themselves and lower when the time is more different
as shown in Table 4. This shows that the entity relatedness gradually change
over time.



Table 4: Correlations of the entity relatedness between different DBpedia
datasets
      Dataset 2008 2009 2010 2011 2012 2013 2014 2015 2016
      2007    0.7141 0.6054 0.4542 0.4762 0.4356 0.4430 0.3856 0.3780 0.3828
      2008           0.7963 0.5748 0.5445 0.5170 0.5488 0.4780 0.4587 0.4620
      2009                  0.6796 0.6334 0.5976 0.6032 0.5532 0.5515 0.5273
      2010                         0.7578 0.6648 0.6692 0.5800 0.5415 0.5188
      2011                                0.8225 0.8186 0.7220 0.6552 0.6385
      2012                                       0.9300 0.8425 0.7498 0.7078
      2013                                              0.8591 0.7700 0.7282
      2014                                                     0.8826 0.8242
      2015                                                            0.9140




5.3   Relatedness with Aggregated Time Information

In order to find how transient links, links that do not persist over different
times, and stable links, links that persist over time, affect the relatedness of the
entities, we constructed different models of aggregated graphs as described in
Section 4.1. We then applied variations of Jaccard methods described previously
and our proposed extended Jaccard similarity with Reciprocal PageRank over
the models.
    Table 5 shows the comparison of Spearman Correlations to the KORE gold
standard of different methods from each dataset over time-varying graphs and
aggregated graphs. ?,∗,∗∗ and ∗ ∗ ∗ show that the results are significantly lower
than the union model with the Extended Jaccard with Reciprocal PageRank
where p-value < 0.1, p-value < 0.05, p-value < 0.01 and p-value < 0.001 respec-
tively. We use P for direct predecessors, S for direct successors, P+S for both
direct predecessors and RP for reciprocal PageRank. We can see that aggre-
gating temporal information as a union graph with the Extended Jaccard with
8
   https://en.wikipedia.org/wiki/Justin_Theroux
9
   http://people.com/celebrity/jennifer-aniston-justin-theroux-engaged/
10
   http://people.com/celebrity/week-ahead-brad-jen-finalize-divorce/
Table 5: The comparison of Spearman Correlations to the KORE gold standard
of different methods from each dataset over time-varying graphs and aggregated
graphs. ?,∗,∗∗ and ∗ ∗ ∗ mean the results are significantly lower than the union
model with the Extended Jaccard with Reciprocal PageRank where p-value <
0.1, p-value < 0.05, p-value < 0.01 and p-value < 0.001 respectively.
                 Jaccard (P) Jaccard (S) Jaccard (P+S) Extended Jaccard RP
    2007         0.434629 ∗ ∗ ∗ 0.398682 ∗ ∗ ∗ 0.447841 ∗ ∗ ∗ 0.444859 ∗ ∗ ∗
    2008         0.501336 ∗∗ 0.476366 ∗∗ 0.526640 ∗           0.514211 ∗
    2009         0.568509 ?     0.511564 ∗∗ 0.578706 ?        0.604112
    2010         0.568026 ∗∗ 0.559898 ∗        0.585535 ∗∗    0.599284 ?
    2011         0.554493 ∗∗ 0.566468 ∗        0.563957 ∗     0.592812 ?
    2012         0.522038 ∗∗ 0.536122 ∗∗ 0.533181 ∗∗          0.559762 ∗
    2013         0.524990 ∗∗ 0.547175 ∗        0.529726 ∗∗    0.562687 ∗
    2014         0.478078 ∗ ∗ ∗ 0.474560 ∗ ∗ ∗ 0.481921 ∗ ∗ ∗ 0.516497 ∗∗
    2015         0.485979 ∗ ∗ ∗ 0.491777 ∗∗ 0.492041 ∗ ∗ ∗ 0.500776 ∗∗
    2016         0.463793 ∗ ∗ ∗ 0.464086 ∗ ∗ ∗ 0.467977 ∗ ∗ ∗ 0.469434 ∗ ∗ ∗
    Intersection 0.360936 ∗ ∗ ∗ 0.351557 ∗ ∗ ∗ 0.361019 ∗ ∗ ∗ 0.352376 ∗ ∗ ∗
    Union        0.567262 ∗     0.501396 ∗∗ 0.535696 ∗∗       0.641174


Reciprocal PageRank gives more relatedness accuracy than the results from each
dataset from time-varying graphs. Intersection graph gives the least relatedness
accuracy to the KORE dataset but it represents entities that are strongly re-
lated to each other at all time. For instance, the top 3 entities with the highest
relatedness scores from the Intersection model with the Extended Jaccard with
Reciprocal PageRank of Apple Inc. are Steve Jobs, IPhone and IMac.


6    Conclusions
We have shown that our proposed graph-based extended Jaccard similarity with
reciprocal PageRank outperforms the baseline text-based approach and graph-
based Jaccard methods. Our relatedness score from DBpedia 2009 and DBpedia
2010, which is the time period when the KORE dataset was created, are the most
correlated to the KORE dataset and using the most recent version of DBpedia
loses a lot of accuracy. This shows that even in a short space of time the eval-
uations made by the annotators of the KORE dataset have become outdated.
However, we show that by aggregating temporal information as one graph, the
accuracy of relatedness is better than any other results from each dataset, demon-
strating the value of considering not just the most recent version of a semantic
graph but also temporal information when performing entity relatedness.

Acknowledgements
This work was supported by Science Foundation Ireland (SFI) under Grant
Numbers SFI/12/RC/2289 (Insight). We would also like to thank Dr. John P.
McCrae for the discussions about this work.
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