peer recommendation using negative relevance feedback

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Peer recommendation using negative relevance feedback DEEPIKA SHUKLA * and C RAVINDRANATH CHOWDARY Department of Computer Science and Engineering, Indian Institute of Technology (BHU) Varanasi, Varanasi 221005, India e-mail: [email protected]; [email protected] MS received 26 May 2021; revised 30 August 2021; accepted 5 October 2021 Abstract. It is a challenging task to recommend a peer to a user based on the user’s requirement. Users may have expertise in multiple sub-domains, due to which peer recommendation is a nontrivial task. In this paper, we model peers as nodes in a graph and perform a community search. Weighted attributes are associated with every node in the graph. We propose two novel methods to compute the weights of the attributes. Relevance feedback is a popular technique used to improve the performance of retrieval systems. We propose to use negative relevance feedback in an attributed graph for peer recommendation. We use CL-tree for indexing the nodes in the graph. We compare the proposed system with the state-of-the-art on standard datasets, and our system outperforms the rival system. Keywords. Peer recommendation; negative relevance feedback; relevance feedback; nnowledge graph; co- authorship network. 1. Introduction Recommendation systems are information filtering systems over dynamically generated large volumes of data that prioritize and personalize the contents. In recent years, many researchers are showing interest in recognizing and characterizing the properties of large-scale graphs [16]. These graph-based techniques are used to improve the performance of the recommender systems [711]. Peer recommendation is a kind of community search [12, 13] problem. The community search in graph science gives the most fitting community containing the query node. By giving attributed query, it provides the most likely com- munity that is matching the query needs. In our context, peer recommendation recommends the most suitable peers for an attributed query. We used a collaboration graph as a knowledge graph to depict all the authors and their collaborations as nodes and edges, respectively. Here, the collaboration graph is some social graph modeling, where a node represents a user, and an edge represents a relationship between two nodes. In figure 1 collaboration graph is created from a coauthor- publication bipartite graph. For example, authors P and Q work together for publication A, so in the co-author network, 1 they will be connected, and their attributes are taken from publication A. Due to the data’s unexpressed nature, the quality of results is unpredictable. Generally, we do not know the output of the model a priori [14]. In peer recommendation for an attributed query, the model should recommend both the direct neighbors of the query node for matching attri- butes/keywords and those peers with similar interests but have not collaborated earlier. The majority of peer rec- ommendation model focuses on nodes that are only reachable through structural cohesiveness [15]. Relevance feedback is a popular technique in retrieval systems to improve performance. We propose to introduce relevance feedback in the recommender system. The majority of the feedback techniques depend on positive or relevant answers. Negative relevance feedback is a particular case of relevance feedback [16]. Here no positive answers are available or provided documents, and answers are assumed to be irrelevant. We use the negative relevance feedback method, which helps to find peers that are not direct neighbors to the query node. The proposed peer recommendation system is person- alized and recommends peers whose interests and exper- tise match the attributes of the query. In this paper, we create an attributed graph and generate an index tree for the graph, which helps in finding the nodes having similar interests as the query node. We propose two features to compute the weight of nodes. These features help in finding the most appropriate peers for the query node. The proposed model provides flexibility in terms of choosing the number of attributes in the query, which impacts the quality of the recommendation. If the recommended list *For correspondence 1 A kind of collaboration graph. Sådhanå (2021) 46:243 Ó Indian Academy of Sciences https://doi.org/10.1007/s12046-021-01763-5

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Peer recommendation using negative relevance feedback

DEEPIKA SHUKLA* and C RAVINDRANATH CHOWDARY

Department of Computer Science and Engineering, Indian Institute of Technology (BHU) Varanasi,

Varanasi 221005, India

e-mail: [email protected]; [email protected]

MS received 26 May 2021; revised 30 August 2021; accepted 5 October 2021

Abstract. It is a challenging task to recommend a peer to a user based on the user’s requirement. Users may

have expertise in multiple sub-domains, due to which peer recommendation is a nontrivial task. In this paper, we

model peers as nodes in a graph and perform a community search. Weighted attributes are associated with every

node in the graph. We propose two novel methods to compute the weights of the attributes. Relevance feedback

is a popular technique used to improve the performance of retrieval systems. We propose to use negative

relevance feedback in an attributed graph for peer recommendation. We use CL-tree for indexing the nodes in

the graph. We compare the proposed system with the state-of-the-art on standard datasets, and our system

outperforms the rival system.

Keywords. Peer recommendation; negative relevance feedback; relevance feedback; nnowledge graph; co-

authorship network.

1. Introduction

Recommendation systems are information filtering systems

over dynamically generated large volumes of data that

prioritize and personalize the contents. In recent years,

many researchers are showing interest in recognizing and

characterizing the properties of large-scale graphs [1–6].

These graph-based techniques are used to improve the

performance of the recommender systems [7–11]. Peer

recommendation is a kind of community search [12, 13]

problem. The community search in graph science gives the

most fitting community containing the query node. By

giving attributed query, it provides the most likely com-

munity that is matching the query needs. In our context,

peer recommendation recommends the most suitable peers

for an attributed query.

We used a collaboration graph as a knowledge graph to

depict all the authors and their collaborations as nodes and

edges, respectively. Here, the collaboration graph is some

social graph modeling, where a node represents a user, and

an edge represents a relationship between two nodes. In

figure 1 collaboration graph is created from a coauthor-

publication bipartite graph. For example, authors P and Q

work together for publication A, so in the co-author

network,1 they will be connected, and their attributes are

taken from publication A.

Due to the data’s unexpressed nature, the quality of

results is unpredictable. Generally, we do not know the

output of the model a priori [14]. In peer recommendation

for an attributed query, the model should recommend both

the direct neighbors of the query node for matching attri-

butes/keywords and those peers with similar interests but

have not collaborated earlier. The majority of peer rec-

ommendation model focuses on nodes that are only

reachable through structural cohesiveness [15]. Relevance

feedback is a popular technique in retrieval systems to

improve performance. We propose to introduce relevance

feedback in the recommender system. The majority of the

feedback techniques depend on positive or relevant

answers. Negative relevance feedback is a particular case of

relevance feedback [16]. Here no positive answers are

available or provided documents, and answers are assumed

to be irrelevant. We use the negative relevance feedback

method, which helps to find peers that are not direct

neighbors to the query node.

The proposed peer recommendation system is person-

alized and recommends peers whose interests and exper-

tise match the attributes of the query. In this paper, we

create an attributed graph and generate an index tree for

the graph, which helps in finding the nodes having similar

interests as the query node. We propose two features to

compute the weight of nodes. These features help in

finding the most appropriate peers for the query node. The

proposed model provides flexibility in terms of choosing

the number of attributes in the query, which impacts the

quality of the recommendation. If the recommended list

*For correspondence 1A kind of collaboration graph.

Sådhanå (2021) 46:243 � Indian Academy of Sciences

https://doi.org/10.1007/s12046-021-01763-5Sadhana(0123456789().,-volV)FT3](0123456789().,-volV)

does not fulfill the predefined criteria, then negative rel-

evance feedback is used to enhance the recommended list

further.

1.1 Motivation

In an attribute-based community search model, the

choice of keywords impacts the retrieved results. If

input keywords are not appropriate, a model is likely to

retrieve irrelevant results. Thus instead of manually

verifying each recommended peer, the relevance feed-

back technique can get adequate results by refining

attributes when needed. To the best of our knowledge,

none of the existing community search literature used

the negative relevance feedback technique over large

dynamic attributed graphs [15] to improve the quality of

the retrieval system. When multiple communities for a

single attributed query are retrieved, it is very tough to

decide which would be a preferable choice. We propose

two features/heuristics to rank and choose an appropriate

community.

1.2 Contributions

• We propose two heuristics to compute the level of

expertise of the peers in the given subdomain.

• We use the negative relevance feedback technique for

community search in a dynamic collaboration graph.

This model refines the initially retrieved result in order

to get better results.

2. Related work

This section concisely reviews some peer recommender

systems and negative relevance feedback based systems.

2.1 Peer recommendation

‘‘It is often necessary to make choices without sufficient

personal experience of the alternatives’’ [17]. A rich part of

the literature on recommender systems is focused on

commercial applications and is categorized into: e-group

activities, e-government, e-commerce/e-shopping, e-li-

brary, e-learning, e-tourism, e-resource services, and

e-business [18]. The recommender systems are broadly

classified into two categories: content-based and collabo-

rative-based recommender systems. A content-based rec-

ommender system works based on the user-provided data,

either implicitly or explicitly [19]. Collaborative methods

recommend items based on the user’s past behavior [20],

where interaction records between users and items are

provided.

Of late, the increase in social activities has increased the

use of the group recommender systems (GRS). ‘‘A group

recommender system is a system that recommends items to

a group of users collectively, given their preferences’’

[21, 22]. Based on the interactions among the group

members, groups can be classified into three categories:

established group [23], random group [24] and occasional

group [25]. The various application domains of GRS

include movie [26], music [27], travel [28], TV programs

[29] etc.

Our major focus is on peer recommendation. Each

domain has different challenges, and the recommender

systems take domain-specific issues into cognizance while

generating the recommendations. This specific kind of

recommender system [30], instead of recommending items

of interest (e-commerce [31]) or friend of a circle (social

platform [32]) to follow, recommends possible collabora-

tion in a specific field of interest based on user’s interest/

requirement.

The authors in [33] spotted a lack of social relationship

(a significant factor of attrition) in Massive Open Online

Courses (MOOCs). They embedded peer recommendations

Figure 1. Attributed co-authorship graph creation from a publication-coauthor bipartite graph.

243 Page 2 of 18 Sådhanå (2021) 46:243

to enhance interaction between students that improve the

quality of learning. They used three different approaches.

These are: random recommendation, socio-demographic

features based, and progress rate in MOOC-based recom-

mendations. The authors analyzed that the recommendation

strategy using socio-demographic information is slightly

more efficient than the random one, whereas the random

recommendation is more efficient than the performance-

based recommendation. They did not consider the dyna-

mism and evolution in students’ requirements. They find

peers based on a similarity measure between learner’s

descriptions that influenced trustworthy relationships and

negatively impacted selecting appropriate members. The

authors in [34] proposed a framework for an online learning

environment aimed to recommend learning peers by using

tripartite graph and CNN.

2.2 Relevance feedback

The feedback mechanism plays a major role in the

quality of retrieved results in text retrieval applications.

Feedback is also used in a content-based image

retrieval system. The relevance feedback method is a

very useful strategy to enhance search accuracy through

feedback. Relevance feedback [35] is basically divided

into three categories i.e. implicit feedback [36], explicit

feedback [37] and blind or pseudo relevance feedback

[38, 39]. Explicit feedback uses either binary (relevant

or irrelevant) or ranking/ratings given on some fixed

scale by the user. Whereas implicit feedback is based

on implicitly captured user’s behavior for retrieved

results. The pseudo relevance automates the feedback

system by considering top k results as relevant and then

expanding query terms accordingly [40]. The negative

relevance feedback method is a special case that is

used when no retrieved results are relevant. Many

researchers explored and used this method in their

respective applications [41–43]. In general, this feed-

back system till now covered various streams, includ-

ing information retrieval [44, 45] and image retrieval

system [46, 47].

[16] discussed general strategies for negative rele-

vance feedback techniques that include query modifica-

tion and score combination strategies. They covered the

language model and vector-space model along with

several heuristics for these methods in negative feedback.

Too much negative feedback may demolish the quality

features of a query. Authors [48] noticed this issue and

then proposed a few strategies used in negative relevance

feedback.

We hypothesize that using negative relevance feedback

may yield good results, and through our experiments, we

show that our model outperforms the rival system.

Table1.

Exam

pleofattribute

weightcomparisionmatrixforauthor‘D

anielGorgen’withattributesset[‘distribute’,‘script’,‘m

obile’,‘application’,‘m

ulti-hop’,‘ad-hoc’,‘network’,

‘generic’,‘background’,‘dissemination’,‘service’,‘geographical’,‘cluster-based’,‘rout’,‘sensing-covered’,‘planar’,‘graph’,‘cluster’,‘inform

ation’,‘m

anagem

ent’,‘m

-learning’,

‘environment’].

Rival_system

Proposed_system

No.

Attributes

Weight

Attributes

Weight

1‘application’,‘network’,‘service’,‘rout’,‘cluster’

16.6196

‘distribute’,‘m

obile’,‘application’,‘service’,‘cluster’

11.6949

2‘distribute’,‘application’,‘network’,‘service’,‘inform

ation’,‘m

anagem

ent’

16.5959

‘distribute’,‘m

obile’,‘network’,‘m

anagem

ent’,‘environment’

39.7761

3‘distribute’,‘m

obile’,‘m

anagem

ent’,‘environment’

27.8614

‘distribute’,‘application’,‘network’,‘service’,‘cluster’

22.1318

4‘m

obile’,‘application’,‘service’,‘rout’,‘cluster’,‘inform

ation’,‘m

anagem

ent’,

‘environment’

2.0559

‘distribute’,‘network’,‘service’,‘rout’,‘inform

ation’

34.1372

Sådhanå (2021) 46:243 Page 3 of 18 243

Table 2. Weight matrix for author ‘Tzu-Kuo Huang’ and keywords [‘generalize’, ‘bradley-terry’, ‘model’, ‘multi-class’, ‘probability’,

‘estimate’].

No. Keyword_set Weight

1 (‘generalize’, ‘multi-class’) 71.4018

2 (‘generalize’, ‘bradley-terry’) 11.8642

3 (‘model’, ‘bradley-terry’) 23.6456

4 (‘multi-class’, ‘probability’) 39.3202

5 (‘multi-class’, ‘estimate’) 50.3420

6 (‘generalize’, ‘model’, ‘multi-class’) 41.0339

7 (‘generalize’, ‘multi-class’, ‘probability’) 13.9467

8 (‘generalize’, ‘multi-class’, ‘estimate’) 13.3776

9 (‘model’, ‘multi-class’, ‘estimate’) 32.1653

10 (‘multi-class’, ‘probability’, ‘estimate’) 13.9442

(a) (b)

Figure 2. Graphs for author ‘Nik Nailah Binti Abdullah’ using negative relevance feedback.

(a) (b)

Figure 3. Graphs for author ‘Xuexiang Huang’ using negative relevance feedback.

243 Page 4 of 18 Sådhanå (2021) 46:243

3. Peer recommendation in dynamic attributedgraphs

In this paper, we model peer recommendation as an

attributed community query (ACQ) [49] problem. Let

G(V, E, X) be an undirected attributed graph along with a

set of edges E and set of vertices V. Here, every node v 2 Vis associated with a set of attributes Xv. For a given

attributed undirected graph G(V, E, X) and a query node

q 2 V with attributes set A, ACQ returns an attributed

community (AC) Gq containing q and Gq � GðV;E;XÞsuch that Gq satisfy structural cohesiveness (i.e., maximal

connectivity among the nodes in Gq) and keyword cohe-

siveness (i.e., all the nodes with x number of keywords in

common).

The graph created in this paper is an attributed co-

authorship graph: a type of collaboration graph of published

articles where attributed nodes are authors/peers that store

information related to their area of interest and expertise,

and a link between two nodes indicate collaboration for an

article. Here the attribute values are dynamic, i.e., when-

ever there is a new link between two nodes, the corre-

sponding attributes’ values get updated. Further, these

attributes and their weights are used to rank the retrieved

communities. The computation of weight is given in

algorithm 1.

3.1 Attributed co-authorship graph creation

Entities in real-life networks have various attributes, and

each attribute has its significance in the relative domain.

Among all attributes of a node, we use some to calculate

the nodes’ interests and expertise. Algorithm 1 describes

the creation of a dynamic attributed co-authorship graph.

Attributes of the nodes in the graph are taken from all the

titles of the author’s publications. Every new publication

can update the list of authors and the associated attributes.

All the authors of a publication pi are represented as a set

Api where Api is list of authors fa1; a2; a3::ang. For everyauthor aj 2 Api , her starting year of publishing ðfyjÞ, totalnumber of publications ðpcjÞ and associated keywords’

attributes (step 2) are computed. If aj 62 G then we add aj to

G and compute its associated attributes’ values. fyj and pcjstores the year of publication ðyrÞ of pi and 1 respectively

ðsteps5� 9Þ. If aj 2 G then for pi, its pcj increments by one

(step 11).

Fa denotes all the keywords of author aj. All the key-

words taken from the title of pi are represented as fpi where

fpi is fk1; k2; k3::kng. If kl 2 fpi and kl 62 Fa then we add kl in

Fa ðsteps13� 15Þ. First-publishing-time ðikyaÞ and latest-

publishing-time ðlkyaÞ of author aj for keyword kl stores yr.

Here, ikya is the initial year when the author started pub-

lishing in a particular keyword kl and lkya is the latest year

when the author published in that keyword. Keyword-fre-

quency ðKkfaÞ of kl is the total number of publications in kl

and initially is set to one ðsteps16� 19Þ. If kl 2 Fa, Kkfa

increases by one and lkya updates by yr ðsteps18� 19Þ .

There are edges between all pairs of vertices of Api in G.

3.2 CL-tree creation

As based on the index, the efficiency of answering ACQ is

improved significantly [48], we create CL-tree for G [49]. It

is an indexed tree-like structure based on the nested k-core2

property where each node contains five attributes. These are

vertex_set (number of vertices of similar nature of con-

nectivity forming that node), parent_node, child_list,

core_number (minimum k-connectivity among all vertices

of that node), and inverted list (features:interested_vertices

pair dictionary). We use an advanced method that follows

the bottom-up approach and is more efficient than the top-

down approach (basic method) regarding real networks for

static CL-tree creation. Initially, we calculate the cores of

all vertices of G, then the recursive creation of nodes of cl-

tree goes from kmax to kmin. Here kmin is zero. All the ver-

tices of ki (kmin � ki � kmax) are considered to find the

number of components formed by these set of vertices.

Each node of the CL-tree denotes a single component of a

particular core number. To address the changes in CL-tree,

we use the incremental learning approach [15] that ensures

2The k � core of a graph is defined as the subgraph in which the

minimum degree of any vertex is k.

Sådhanå (2021) 46:243 Page 5 of 18 243

adding nodes and edges in CLtree at runtime environment.

Detailed explanation of CL-tree creation is given in [48].

3.3 Peer recommendation

We query the model in the form of (q, k, A). Here q is the

query node, k is the core number, and A is the set of

attributes. We search q in the CL-tree, and the core number

of this node should be greater than or equal to k. k in the

query indicates the process of community search, involves

only nodes3 having at least k-core. We use the decremental

algorithm discussed in [12] for community search. The

decremental algorithm uses attributes of a for searching

communities. After applying a community search, we may

get multiple communities, and these communities may have

single or multiple peers for a subset of attributes.

3.4 Weighted community

The retrieved communities include peers with homoge-

neous attributes. A node of the graph can have multiple

interests, leading her into multiple communities with dif-

ferent keywords. We address two issues with the help of

weighing the community:

1. For an attributed query, the model may give multiple

communities for a subset of query attributes.

2. If there are multiple collaborators for a single publica-

tion, the result can fulfill the maximum keyword

cohesiveness and structural cohesiveness even in the

case of very few publications of the involved peers in the

received community.

So, to select the best community, we have proposed two

heuristics to weigh communities. We further use these

weights to rank and choose the best community.

(a) (b)

Figure 4. Graphs for author ‘Yaun-Zhi Song’ for results validation.

(b)(a)

Figure 5. Graphs for author ‘Yousuke Hagiwara’ for results validation.

3CL-tree nodes.

243 Page 6 of 18 Sådhanå (2021) 46:243

1. Importance(I): Importance Ika of a node a in a subdo-

main k is computed as given in equation 1. Any node’s

importance is measured by the percentage of the total

number of publications in a particular area to the total

publication duration in that area. Here duration is the

period of continuation in a particular area. Equation 1 is

used to calculate the Ika , where Kkf a

denotes the total

number of publications by a in a particular field4 k.Duration of that publication is given by the difference to

the first time she published an article ðfkeyaÞ in a

subdomain to the time she published her latest publica-

tion ðlkkeyaÞ in the same subdomain.

If there are d co-authors with respect to publication pi, allthese d co-authors will have at least d � 1 co-authors in

G. If one of the d co-authors is publishing for the first

time, even then, her connectivity will be d � 1, so, Itakes care of this issue.

Ika ¼ Kkf a=durationpub; durationpub ¼ ðlkya � f kya þ 1Þ

ð1Þ2. Attention(T): The attention Tk

a of an author with respect

to the particular field is computed as given in equation 2,

i.e., the ratio of the publication count Kkf a

regarding a

particular area to the total number of author’s publica-

tions ðEpubaÞ till date.

Tka ¼ Kk

f a=Epuba ð2Þ

Wak ¼Xn

i¼1

ða:Rkaiþ b:Pk

aiþ c:Tk

aiþ h:IkaiÞ ð3Þ

Both the features help to identify the potential of the

nodes. If the number of authors in a qualified community

are n then the weights of each keyword for every node of

that community is calculated by equation 3 where the

values of a, b, c, and h are fixed empirically. All the

values lie between 0 and 1. Here relevance ðRkaÞ and

proximity ðPkaÞ [15] give activeness in a particular

research area and nearness of publication in that area,

respectively. The collective sum of a, b, c and h is 1.

SðKjÞ ¼Xm

k¼1

Wak=m ð4Þ

The weight of the community is later measured by the

cumulative weight of every member of the community.

For every community, equation 4 gives the normalized

score assigned to each keyword set. The score is calcu-

lated as the ratio of the cumulative sum of weight

assigned to every keyword in the keyword set to the total

number of keywords in that set (Table 1). Here, Kj refers

to the j th keyword set, and Wak refers to the weight of

author for k th keyword. Keyword cohesiveness is sat-

isfied by every community.

3.5 Relevance feedback

We use equation 5 to check the relevance of the received

community. It uses the neighborhood property. If all the

received nodes are direct neighbors of the query node, they

already worked with it. We use the negative relevance

feedback technique to explore new nodes having a similar

interest as the query node. If the score of community

S(q, C) for community C is greater than or equal to one,

some nodes are in the community that has never worked

before with the query node. Otherwise, query keywords

need refinement [16], and we penalize all the members of

Figure 6. Process diagram for peer recommendation.

4Here, the field is a keyword and each keyword is considered to

calculate Ika . Attribute, keyword, and field are interchangeably used.

Sådhanå (2021) 46:243 Page 7 of 18 243

the initially retrieved community for getting a better

response. In equation 5, NG½q� represents direct neighboursof node q in G and Cpeer denotes peers in the community C.

Sðq;CÞ ¼ jfv : v 2 Cpeer; v 62 NG½q�gj ð5ÞAs shown in figure 6, the process flow diagram gives a

complete flow of peer recommendation.

• Step 1: Attributed query is applied in the attributed

graph to get an efficient community.

• Step 2: The initially retrieved community is evaluated

for its keywords length5 and community length.6

• Step 3: If any of the above evaluations fail, then go for

a new query model by replacing irrelevant keywords

(a)

(b)

Figure 7. Sample recommendation graphs by the proposed system.

5The number of common keywords should be greater than one.6The number of nodes in the retrieved community must be greater

than or equal to two.

243 Page 8 of 18 Sådhanå (2021) 46:243

with the most appropriate keywords from the corpus

using the word2vec7 model.8

• Step 4: If the community satisfies the taken standards

for community strength, then we check the commu-

nity’s relevance.

• Step 5: If a community does not contain any new node

for the user, use negative relevance feedback that

penalizes all the community members. Replace the

keywords as described in step 3.

• Step 6: Again, we do a community search with a new

query model and go for step 2. Suppose the retrieved

community passes all three parameters. In this case,

that will be the final result, and the community with

the highest weight will be recommended.

Steps 1 to 6 are repeated at most five times.

4. Experimental setup and results

We perform experiments using dblp9 dataset. Each attri-

bute is associated with two timestamps. They are a year in

which the author published for the first time, and the

second is the most recent year the author published in the

particular field. Another attribute for the keyword is the

number of publications in that field (the field is identified

using the keyword. we assume that each keyword is a

separate field). The time attribute of a node is taken from

the year of publication. The words present in the title of

the publication are taken as attributes of interest. We filter

out the title by removing stop words10 and acronyms,11

then take more generalized words by stemming12 each

word. We take two dblp dataset samples where set1 is for

the years 2004–2008 and set2 for the years 2009–2013.

Every created graph has around 2M vertexes and 8M edges

in it. All the experiments are done on a CPU node of the

ParamShivay supercomputer, having an IntelXeonSKLG�6148 processor and 192GB of memory with a Linux

operating system. All the algorithms are implemented in

python. The retrieved results for set1 and set2 are repre-

sented as retrieved and relevant results, respectively.

4.1 Effectiveness evaluation

4.1.1 Effect of attribute weightIn this model, the importance given to the features is

determined a, b, c, and h. We empirically fixed the values

of a as 0.15, b as 0.15, c as 0.35, and h as 0.35. The

Table

3.

Exam

plesfornegativerelevance

feedback.

No.

Query_node

Initial_Keywords

Initial_Retrieved_community

Figure

2a

Nik

NailahBintiAbdullah

‘analysis’,‘synthesis’,‘learn’,‘agent’,‘communicative’,‘behavior’

‘StefanoA.Cerri’,‘N

ikNailahBintiAbdullah’

Figure

3a

XuexiangHuang’

‘special’,‘issue’,‘2006’,‘npa’

‘G.Y.Chen’,‘X

inmin

Yang’,‘X

uexiangHuang’

No.

New

_keyworks

Final_retrived_results

Figure

2b‘im

prove’,‘umts’,‘decision’,‘resource’,‘verification’,

‘m.s’

‘RolandoA.Carrasco’,‘Sam

uel

Pierre’,‘A

lejandro

Quintero’

Figure

3b‘introduction’,‘press’,‘8-cycle’

‘Jorg

Rothe’,‘A

ndrew

Whitworth’,‘K

angZhang’,‘D

enisBouyssou’,‘Sim

onParsons’,‘Francesca

Rossi’,‘JosC.M.Baeten’,‘M

ikaH

irvensalo’,‘Jonathan

Cohen’,‘G

heorgheMuresan’,‘M

ileK.Stojcev’,

‘IsabelNavazo’,‘Jonathan

Katz’,‘Frederic

Loulergue’,‘PaulDourish’,‘H

ugodeG

aris’,‘Tim

Oates’,

‘DanielMerkle’,

‘Law

rence

S.Moss’,‘M

atthew

Chalmers’

7https://code.google.com/archive/p/word2vec/.8It gives the most similar word for any keyword.9http://dblp.uni-trier.de/xml/.10https://en.wikipedia.org/wiki/Stop_word.11https://en.wikipedia.org/wiki/Acronym.12https://en.wikipedia.org/wiki/Stemming.

Sådhanå (2021) 46:243 Page 9 of 18 243

retrieved result has multiple communities, but our selection

model selects the best community. The number of common

keywords is not the only criteria to select the community

(figure 7).

Table 2 gives weights of the retrieved keyword sets for

the author ‘Tzu-Kuo Huang’. We observe that the size of

keyword sets is at most three. Though the sets of size three

are available, the model has chosen the set of size two. The

keyword set (generalize, multiclass) has more publication

in a short duration, and our model intelligently chooses this

keyword set.

4.1.2 Effect of negative relevance feedbackTable 3 shows some results after applying negative

feedback to see the effectiveness of the negative

relevance feedback. We consider all the direct neighbors

as negative points. Here relevance is measured by using

equation 5. Figures 2 and 3 give the communities for the

queries ‘Nik Nailah Abdullah’ and ‘Xuexiang Huang’,

respectively. As we can see, figures 2a and 3a are connected

to all their neighbors. The system suggests no new peers.

To get a new community, we update query keywords. After

applying negative relevance feedback, we get communities

given in figures 2b and 3b respectively. The connectivity

for every node of the retrieved community is not

compulsory as individuals are retrieved because of

keyword cohesiveness, and all the initially retrieved peers

are penalized, whereas the query node will remain intact.

The retrieved results are connected in the real graph by

nested core property.

4.1.3 Accuracy validationWe use retrieved results for recommendation and relevantresults to validate recommendations. Here validation is to

check whether the query node is using suggested peers in

the future. We take three sets of randomly selected 1000

authors and apply peer recommendations for these selected

authors. Table 4 shows a few examples of validation

process where the retrieved_community has the final peer

recommendations, and relevant_community has the actual

collaborations for the same query based on the dataset set2.

Results are illustrated in figures 4 and 5 for authors ‘Yuan-

Zhi Song’ and ‘Yousuke Hagiwara’ respectively.

Figures 4a and 5a show original peer recommendations

Table 4. Examples for validating the results.

No. Query_node Keywords

Figure 4 ‘Yuan-Zhi Song’ ‘theoretical’, ‘analysis’, ‘retention’, ‘behavior’, ‘high-performance’,

‘liquid’, ‘pigment’, ‘chromatographic’, ‘reversed-phase’, hplc’

Figure 5 ‘Yousuke Hagiwara’ ‘clock’, ‘driver’, ‘design’, ‘low-power’, ‘high-speed’, ‘90-nm’, ‘cmos’,

‘register’, ‘array’

No. Retrieved_community

Figure 4a ‘Yang Song’, ‘Jian-Feng Zhou’, ‘Jiming Xie’, ‘Yong Ye’, ‘Yuan-Zhi

Song’

Figure 5a ‘Yousuke Hagiwara’, ‘Tadayoshi Enomoto’, ‘SuguruNagayama’,

‘Hiroaki Shikano’

No. Relevant_community

Figure 4b ‘Ji-Min Xie’, ‘Jian-Feng Zhou’, ‘Yuan-Zhi Song’, ‘Yong Ye’, ‘Feng-Xia Zhu’

Figure 5b ‘Makoto Takahashi’, ‘Takayoshi Shimazawa’, ‘Hideho Arakida’, ‘Manabu Watanabe’, ‘Hirokazu

Ezawa’, ‘Hiroyuki Hara’, ‘Masatoshi Fukuda’, ‘Tomohisa Maeda’, ‘Yu Kikuchi’, ‘Hideaki Yamamoto’, ‘Masafumi

Takahashi’, ‘Yousuke Hagiwara’, ‘Yasuo Ohara’, ‘Yasuhiro Koshio’, ‘Mototsugu Hamada’, ‘Takashi Miyamori’,

‘Tetsuya Fujita’, ‘Yukihito Oowaki’

Table 5. Average performance matrix (in %) for 1000-random

AuthorSet1.

Precision Recall

Rival system 17.948571 17.351479

Proposed system 19.964588 19.190202

Table 6. Average performance matrix (in %) for 1000-random

AuthorSet2.

Precision Recall

Rival system 16.252593 16.331243

Proposed system 18.851046 18.944374

Table 7. Average performance matrix (in %) for 1000-random

AuthorSet3.

Precision Recall

Rival system 13.251771 13.441303

Proposed system 16.276614 16.529017

243 Page 10 of 18 Sådhanå (2021) 46:243

for a sample attributed query set. Whereas figures 4b and 5b

show the actual collaborations for the above query set

(based on the dataset set2). We present one random fifty

authors set results in Appendix A, where N.A. denotes

authors not available. We use precision and recall to

measure the accuracy of recommendations.

Suppose Aia is the retrieved recommendation for an

author a in a query i , and Bia is a relevant recommendation.

If the number of queries are m:

precisionia ¼ nðAia \ BiaÞ=nðAiaÞ ð6Þ

recallia ¼ nðAia \ BiaÞ=nðBiaÞ ð7Þ

Average precision ¼ ðXm

l¼1

precisionlaÞ=m ð8Þ

Average recall ¼ ðXm

l¼1

recalllaÞ=m ð9Þ

We compared the proposed system with our earlier system

[15]. We calculate precision and recall for all the random

1000 AuthorSeti. We use equation 6 and equation 7 to

calculate the precision and recall respectively for each

author in every AuthorSeti. Equations 8 and 9 are used to

calculate the average precision and average recall respec-

tively. The average precision and average recall of

AuthorSet1, AuthorSet2 and AuthorSet3 are given in

tables 5, 6 and 7 respectively. From our experiments, we

observed that authors are not only exploring the peers in the

area they worked in the past but also exploring the peers

from the new areas of interest.

Our observations based on the results of the proposed

model:

1. In this model, the graph ensures dynamism by updating

its attributes whenever any change occurs in the graph.

2. The final retrieved community need not be connected.

The nodes are connected in the real graph because of the

co-authorships, but the retrieved community has to

satisfy only the keyword cohesiveness property. It can

make member nodes disconnected, as they could not

work together for related attributes.

3. This model has a certain degree of robustness due to the

proposed query reformulation strategy.

We have included the results based on three sets of 1000

random queries. We select random queries along with their

attributes. The random selection of queries from two mil-

lion nodes is time-consuming and complex to the system.

The average running time for each query is 4.32 seconds.

We experimented on three random sets of sizes 150, 350,

500, and 1000 query sets and included the results of 1000

random queries in this paper. We found that the trend in the

results is similar for all these query sets irrespective of the

size of the sets.

5. Conclusion

In this paper, we model peer recommendation as an

attributed community query (ACQ) problem. Peer recom-

mendation is performed over dynamic graphs that ensure

updations of the data. We propose two features named

importance and attention to measuring the expertise of a

peer in a subdomain. Also, we propose to use negative

relevance feedback for community search in a dynamic

collaboration graph. Using these approaches, we refine peer

recommendation where each peer is interested in the same

knowledge as the peer seeker, and some or all have

expertise in it. The model checks the relevance of recom-

mendations that make this system effective when no rele-

vant peers are received. Our model refines the initially

retrieved results through query reformulation in order to get

better results. To the best of our knowledge, this is the first

attempt to use negative relevance feedback for query

reformulation in peer recommendation. Our results are

encouraging.

There are multiple ways to improve the performance of

the proposed model-

(a) We would like to explore the performance of the

proposed model by using intelligent machine learning-

based algorithms.

(b) We intend to apply the peer recommendations to other

collaboration graphs (for example, peer recommenda-

tion in sports graph) with respective domain-specific

features.

(c) To find a better trade-off among importance, attention,

relevance, and proximity will be exciting work.

(d) The current features of an author are taken from the

titles of the publications. This may result in inadequacy

about the interest of an author. The way of getting better

attributes is to take attributes from the title and abstract

of publications.

Appendix A Results for peer recommendation

See Table 8.

Sådhanå (2021) 46:243 Page 11 of 18 243

Table

8.

Retrieved

andrelevantcommunitiesforfifty

random

sample

queries.

No.

Query_node

Query_attributes

Retrieved_Peers

Relevant_Peers

1V.S.Meenakshi

inform

ation’,‘technology’,‘business’,‘decision’,‘m

ake’,

‘managem

ent’

A.L.Suseela’,‘B.PradeepKumar’,‘K

.

Kanthi’,‘V

.LalithKumar’,‘John

Selvam

’,‘V

.S.Meenakshi’

‘G.Padmavathi’,‘V

.S.Meenakshi’

,‘K.Kanthi’

2XavierIntes

extend’,‘kalman’,‘filter’,‘m

odel’,‘analysis’,‘tumor’,

‘use’,‘optical’,‘m

ethod’,‘pharmacokinetics’,‘nir’,‘icg’,

‘cancerous’

‘BirsenYazici’,‘X

avierIntes’,‘Burak

Alacam’,‘BrittonChance’

‘Vivek

Venugopal’,‘Jin

Chen’,

‘XavierIntes’,‘M

onish

Pim

palkhare’,‘BurakAlacam’,,

‘BirsenYazici’

3NorHayatiOthman

automate’,‘cervical’,‘pre-cancerous’,‘diagnostic’,

‘system

Mohd.Yusoff

Mashor’,‘N

orHayati

Othman’,‘N

orAshidiMat

Isa’

‘SitiNorainiSulaim

an’,‘N

orAshidi

Mat

Isa’,‘N

orHayatiOthman’

4XuexiangHuang

special’,‘issue’,‘2006’,‘npa’

G.Y.Chen’,‘X

inmin

Yang’,‘X

uexiang

Huang’

‘XuexiangHuang’,G.Y.Chen’,

‘Xinmin

Yang’

5Janet

S.Sinsheimer

garden’,‘branching’,‘process’

KennethLange’,‘K

arin

S.Dorm

an’,‘Janet

S.Sinsheimer’

‘KennethLange’,‘Janet

S.

Sinsheimer’,‘H

uaZhou’,‘K

arin

S.

Dorm

an’

6CarlF.Mela

building’,‘brand’,‘online’,‘auction’,‘dem

and’,

‘database’,‘paper’,‘m

arketing’,‘data’,‘set’,‘iri’

‘CarlF.Mela’,‘Chung-W

eiLi’,‘EricW.

T.Ngai’,‘PilarSancho’,‘JudyC.

R.Tseng’,‘Bertvan

den

Berg’,‘Jam

esJ.

Cappel’,‘N

icola

Henze’

‘CarlF.Mela’,‘JillJameson’,‘C.

Miller’,‘V

ishal

Midha’,‘Hyochang

Lim

’,‘Szu-Y

uan

Sun’,‘Frederico

C.Figueiredo’,‘Chung-W

eiLi’,

‘EricW.T.Ngai’,‘Pilar

Sancho’,

‘JudyC.R.Tseng’,‘Bertvan

denBerg’,‘Jam

esJ.Cappel’,‘N

icola

Henze’,‘Y

ueh-M

inHuang’,‘Jose

Janssen’,‘A

drian

Mee’,‘BeckySiu’,

‘SergioMiranda’,‘Jaume

Casadesus’,‘M

argitPohl’,‘M

aria

FrancescaCostabile’

7Yuan-ZhiSong

theoretical’,‘analysis’,‘retention’,‘behavior’,‘high-

perform

ance’,‘liquid’,‘pigment’,‘chromatographic’,‘

reversed-phase’,‘hplc’

‘YangSong’,‘Jian-FengZhou’,‘Jim

ing

Xie’,‘Y

ongYe’,‘Y

uan-ZhiSong’

Ji-M

inXie’,‘Jian-FengZhou’,‘Y

uan-

ZhiSong’,‘Y

ongYe’,‘Feng-X

ia

Zhu’

243 Page 12 of 18 Sådhanå (2021) 46:243

Table

8.

continued

No.

Query_node

Query_attributes

Retrieved_Peers

Relevant_Peers

8YousukeHagiwara

clock’,‘driver’,‘design’,‘low-power’,‘high-speed’,‘90-

nm’,‘cmos’,‘register’,‘array’

YousukeHagiwara’,‘Tadayoshi

Enomoto’,‘SuguruNagayam

a’,‘H

iroaki

Shikano’

‘Makoto

Takahashi’,‘Takayoshi

Shim

azaw

a’,‘HidehoArakida’,

‘ManabuWatanabe’,‘H

irokazu

Ezawa’,‘H

iroyukiHara’,‘M

asatoshi

Fukuda’,‘TomohisaMaeda’,‘Y

u

Kikuchi’,‘H

ideakiYam

amoto’,

‘MasafumiTakahashi’,

‘YousukeH

agiwara’,‘Y

asuoOhara’,

‘YasuhiroKoshio’,‘M

ototsugu

Ham

ada’,‘TakashiMiyam

ori’,

‘TetsuyaFujita’,‘Y

ukihitoOowaki’

9Andreas

Muller’

real-tim

e’,‘statistic’,‘baustein’,‘fur’,‘ein’,‘selbst’,

‘verwaltendes’,‘datenbanksystem

’,‘db2’,‘z/os’,‘und’,

‘os/390’

‘DanielCruz-Suarez’,‘RaulMontes-de-

Oca’,‘EnriqueLem

us-Rodriguez’

‘Andreas

Muller’,‘RobertVilzm

ann’,

‘LajosH

anzo’,‘ChristianHartm

ann

0001’,‘K

atsutoshiKusume’,

‘GerhardBauch

0001’

10

DanielCruz-Suarez

discount’,‘m

arkov’,‘decision’,‘process’,‘condition’,

‘uniqueness’,‘optimal’,‘policy’

FranciscoSalem

-Silva’,‘D

anielCruz-

Suarez’,‘RaulMontes-de-Oca’

‘DanielCruz-Suarez’,‘RaulMontes-

de-Oca’,‘EnriqueLem

us-

Rodriguez’

11

HuiZhuang

(‘complete’,‘nucleotide’,‘sequence’,‘hepatitis’,‘virus’,

’isolated’,‘xinjiang’,‘epidem

ic’,‘1986-1988’,‘china’

‘FusaeIida’,‘H

uiZhuang’,‘Toshikazu

Uchida’,‘TheinT.Aye’,‘Toshio

Shikata’,

‘Xue-ZhungMa’,‘K

hin

MaungWin’

N.A.

12

Per-O

lofWestlund

quantum’,‘description’,‘stern-gerlach’,‘experim

ent’

‘Per-O

lofWestlund’,‘H

akan

Wennerstrom’

N.A.

13

DasariKarunaSagar

point’,‘spread’,‘function’,‘optical’,‘system

’,‘apodized’,

‘sem

icircular’,‘array’,‘aperture’,‘asymmetric’,

‘apodization’

‘DasariKarunaSagar’,‘A

ndra

Naresh

Kumar

Reddy’

N.A.

14

W.R.Walter

large-scale’,‘seism

ic’,‘signal’,‘analysis’,‘hadoop

‘DouglasA.Dodge’,‘T.G.Addair’,‘W

.

R.Walter’,‘StanD.Ruppert’

N.A.

15

Jose

GuilhermeCecatti

mobile’,‘technology’,‘health’,‘m

health’,‘antenatal’,

‘care-searching’,‘apps’,‘available’,‘solution’,

‘system

atic’,‘review’

‘Jose

GuilhermeCecatti’,‘Sam

iraM.

Haddad’,‘RenatoT.Souza’

N.A.

16

DianeMichelfelder

sustain’,‘engineering’,‘code’,‘ethic’,‘twenty-first’,

‘century’

‘DianeMichelfelder’,‘SharonA.Jones’

N.A.

17

MuneerahR.Aldhafian

toward’,‘design’,‘li-fi-based’,‘hierarchical’,‘iot’,

‘architecture’

‘Afnan

A.Aljaser’,‘Lam

iaAl-Braheem’,

‘Lam

iaH.Alhudaithy’,‘M

uneerahR.

Aldhafian’,‘G

hadaM.Bahliwah’

N.A.

Sådhanå (2021) 46:243 Page 13 of 18 243

Table

8continued

No.

Query_node

Query_attributes

Retrieved_Peers

Relevant_Peers

18

AkihikoTaw

ara

tolerance’,‘range’,‘binocular’,‘disparity’,‘‘display’,

‘base’,‘physiological’,‘characteristic’,‘ocular’,

‘accommodation’

‘TsunetoIw

asaki’,‘A

kihikoTaw

ara’,

‘ToshiakiKubota’

N.A.

19

Yuan

Hou

redundant’,‘heterogeneity’,‘group’,‘perform

ance’

‘LiliTian’,‘Y

ingLiu’,‘Y

angLi’,‘Y

uan

Hou’,‘Lei

Liu’,‘EdwardBishopSmith’,

‘AthanasiosV.Vasilakos’,‘Tao

Zhou’,

‘Yao

Wang0001’

N.A.

20

RebekkaS.Renner

perception’,‘egocentric’,‘distance’,‘virtual’,

‘environment’,‘review’

‘JingWang’,‘Jean-Louis

Vercher’,

‘RebekkaS.Renner’,‘Christophe

Bourdin’,‘BorisM.Velichkovsky’,‘‘Jens

R.Helmert’

N.A.

21

DominikaPolkowska

pac’,‘bound’,‘substructure’,‘stable’,‘structure’

‘Sanjeev

R.Kulkarni’,‘D

ominika

Polkowska’,‘A

nandPillay’

N.A.

22

Peter

Tomaszewski

mismatch’,‘sim

ulation’,‘layout’,‘sensitive’,‘param

eter’,

‘component’,‘device’

‘LiZhang’,‘G

erhardTroster’,‘Peter

Tomaszewski’

N.A.

23

MariosPolitis

analysis’,‘dynam

ical’,‘m

odel’,‘hiv’,‘infection’,‘one’,

‘two’,‘input’

‘MariosPolitis’,‘Ioannis

Kafetzis’,

‘LazarosMoysis’

N.A.

24

RichardS.Drake

survey’,‘video’,‘gam

e’,‘preference’,‘adult’,‘building’,

‘well’,‘old’

‘JoshuaP.Salmon’,‘RichardS.Drake’,

‘GailA.Eskes’,

N.A.

25

TiefengPeng

surface’,‘interaction’,‘nanoscale’,‘w

ater’,‘film

’,

‘computational’,‘sim

ulation’,‘thermodynam

ics’

‘Chao

He’,‘LonghuaXu’,‘Q

ibin

Li’,

‘LiqunLuo’,‘TiefengPeng’

N.A.

26

Basavaraj

Hirem

ath

bayesian’,‘approach’,‘alignment’,‘high-resolution’,

‘nmr’,‘spectrum’

‘SeoungBum

Kim

’,‘BasavarajHirem

ath’,

‘ZhouWang’

N.A.

27

JiguangZhu

new

’,‘approach’,‘detect’,‘active’,‘rule’,‘confluence’,

‘exclusive’,‘process’,‘indeterminable’

‘HongchunYuan’,‘ShijunHe’,‘H

uiwen

Wei’,‘Zhongmin

Xiong’,‘JiguangZhu’

N.A.

28

HuanglongTeng

multi-hop’,‘delay’,‘reduction’,‘safety-related’,‘m

essage’,

‘broadcasting’,‘vehicle-to-vehicle’,‘communication’

‘Hongbin

Chen’,‘Bin-Jie

Hu’,‘X

iaohuan

Li’,‘H

uanglongTeng’,‘BingLi0016’,

‘Manman

Cui’

N.A.

29

Kevin

K.Parker

actuator’,‘robotics’,‘review’,‘device’,‘actuate’,‘living’,

‘cell’,‘biohybrid’

‘Paolo

Dario’,‘RituRam

an’,‘K

evin

K.

Parker’,‘A

riannaMenciassi’,‘Rashid

Bashir’,‘M

etin

Sitti’,‘Barry

Trimmer’,

‘SylvainMartel’,‘A

dam

W.Feinberg’

N.A.

30

HongjingLiu

analytical’,‘study’,‘m

ulti-tier’,‘heterogeneous’,‘small’,

‘cell’,‘network’,‘coverage’,‘perform

ance’,‘energy’,

‘efficiency’

‘ZhuHan’,‘TongLi0013’,‘H

ongjing

Liu’,‘M

oham

ed-Slim

Alouini’,‘V

ictorC.

M.Leung’,‘Ekram

Hossain’,‘D

ongWang

0016’,‘ZhuXiao’,‘Rahim

Tafazolli’,

‘VincentHavyarim

ana’

N.A.

31

RuiShantilau

socio-technical’,‘approach’,‘address’,‘inform

ation’,

‘security’,‘use’,‘m

anager’,‘artefact’,‘27001’

‘RuiShantilau’,‘A

nacleto

Correia’,

‘Antonio

Goncalves’

N.A.

243 Page 14 of 18 Sådhanå (2021) 46:243

Table

8continued

No.

Query_node

Query_attributes

Retrieved_Peers

Relevant_Peers

32

E-LingLou

transition’,‘ipv6’,‘support’,‘ipv4/ipv6’,‘interoperability’,

‘ims’

‘DupyoChoi’,‘A

nneY.Lee’,‘Chung-Zin

Liu’,‘E-LingLou’,‘ChristineFischer’,

‘Hsien-Chuen

Yu’

N.A.

33

Erich

Thanhardt

national’,‘center’,‘atm

ospheric’,‘research’,‘storage’,

‘accounting’,‘analysis’,‘possibility’

‘David

L.Hart’,‘Erich

Thanhardt’,‘Pam

Gillm

an’

N.A.

34

Melanie

Kam

mermann

australia’,‘health’,‘library’,‘future’,‘research-directed’

‘CarolNew

ton-Smith’,‘SuzanneLew

is’,

‘CherylHam

ill’,‘M

elanie

Kam

mermann’,

‘Gillian

Hallam’,‘‘Patrick

O’Connor’’,

‘AnnRitchie’

N.A.

35

David

Stoops

tool’,‘design’,‘shape’,‘3-draw’

David

Stoops’,‘Emanuel

Sachs’,‘A

ndrew

Roberts’

N.A.

36

Vlad-RaulPasca

challenge’,‘cyber’,‘security’,‘ransomware’,

‘phenomenon’

‘EmilSim

ion’,‘A

runKumar

Sangaiah’,

‘Vlad-RaulPasca’

N.A.

37

Anatoly

S.Apartsin

test’,‘volterra’,‘equation’,‘first’,‘kind’,‘integral’,

‘model’,‘develop’,‘system

’,‘use’,‘nonclassical’

‘InnaV.Sidler’,‘A

natoly

S.Apartsin’

N.A.

38

Dragoslav

Herceg

fourth-order’,‘finite-difference’,‘m

ethod’,‘singularly’,

‘perturbed’,‘boundary’,‘value’,‘problem’

‘Dragoslav

Herceg’,‘D

jordje

Herceg’

N.A.

39

J.L.Carrillo

optical’,‘quantum’,‘w

ell’,‘effect’,‘base’,‘intersub-band-

transitions’

‘J.Bohorquez’,‘R.M.Gutierrez’,‘J.

L.Carrillo’,‘A

.S.Cam

acho’

N.A.

40

AggelikiPapapanagiotou-

Leza

implement’,‘e-justice’,‘national’,‘scale’,‘cop’,

‘balkanization’,‘socio-economical’,‘divergence’

‘GeorgeChristou’,‘Panagiotis

Giannakopoulos’,‘G

eorgeDonos’,

‘DionysiosPolitis’,‘A

ggeliki

Papapanagiotou-Leza’

N.A.

41

Kin-ChungWong

optimal’,‘linear’,‘combination’,‘facial’,‘region’,

‘improve’,‘identification’,‘perform

ance’

‘Wei-Y

angLin’,‘N

igel

Boston’,‘X

ueqin

Zhang’,‘K

in-ChungWong’,‘Y

uHen

Hu’

N.A.

42

ElenaNavarro

Gonzalez

data’,‘w

arehouse’,‘improve’,‘w

eb-based’,‘learn’,‘site’

‘ElenaNavarro

Gonzalez’,‘LuisMartinez-

Lopez’,‘FranciscoAraqueCuenca’,

‘Alberto

SalgueroHidalgo’,‘M

aria

DoloresCaleroGarcia’

N.A.

43

Janet

S.Sinsheimer

garden’,‘branching’,‘process’

KennethLange’,‘K

arin

S.Dorm

an’,‘Janet

S.Sinsheimer’

N.A.

44

XuexiangHuang

special’,‘issue’,‘2006’,‘npa’

‘G.Y.Chen’,‘X

inmin

Yang’,‘X

uexiang

Huang’

N.A.

45

Nik

NailahBintiAbdullah

analysis’,‘synthesis’,‘learn’,‘agent’,‘communicative’,

‘behavior’

‘StefanoA.Cerri’,‘N

ikNailahBinti

Abdullah’

N.A.

46

IanMullins

extend’,‘cyberspace’,‘location’,‘base’,‘gam

e’,‘use’,

‘cellular’,‘phone’

‘Ian

Mullins’,‘Reuben

Edwards’,‘O

mer

Rashid’,‘PaulCoulton’

N.A.

47

MichaelJohnBarclay

comparison’,‘region’,‘approxim

ation’,‘technique’,‘base’,

‘delaunay’,‘triangulation’,‘voronoi’,‘diagram’

‘MichaelJohnBarclay’,‘A

ntonyGalton’

N.A.

Sådhanå (2021) 46:243 Page 15 of 18 243

Acknowledgements

The support and the resources provided by ‘PARAM

Shivay Facility’ under the National Supercomputing Mis-

sion, Government of India at the Indian Institute of

Technology, Varanasi are gratefully acknowledged.

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Table

8continued

No.

Query_node

Query_attributes

Retrieved_Peers

Relevant_Peers

48

HironobuKaw

akoe

estimation’,‘contact’,‘shape’,‘quadric’,‘environment’,

‘object’,‘probe’,‘operation’

HironobuKaw

akoe’,‘Showzow

Tsujio’,

‘YoshiyukiKam

o’,‘Y

ongYu0003’

N.A.

49

Hongwei

Cheng

compression’,‘low’,‘rank’,‘m

atrix’,‘w

ideband’,‘fast’,

‘multipole’,‘m

ethod’,‘helmholtz’,‘equation’,‘three’,

‘dim

ension’

‘Zydrunas

Gim

butas’,‘V

ladim

irRokhlin’,

‘Hongwei

Cheng’

N.A.

50

AgnieszkaSwierczewska

flow’,‘incompressible’,‘fluid’,‘discontinuous’,‘rheology’,

‘large’,‘eddy’,‘sim

ulation’,‘turbulence’,‘m

odel’,

‘young’,‘m

easure’,‘power-law

-like’

‘PiotrGwiazda’,‘A

gnieszka

Swierczewska’

N.A.

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