Community Focused Social Network Extraction
Masahiro Hamasaki1 , Yutaka Matsuo1 , Keisuke Ishida1 , Yoshiyuki Nakamura1 ,Takuichi Nishimura1 , and Hideaki Takeda2
1

National Institute of Advanced Industrial Science and Technology (AIST),Tokyo, Japan
2
National Institute of Informatics (NII),
2-1-2 Hitotsubashi, Chiyoda-ku Tokyo, Japan

Abstract. A social networking service can become the basis for the information infrastructure of the future. For that purpose, it is important
to extract social networks that reflect actual social networks which users
have already had. Providing a simple means for users to register theirsocial relations is also important. We propose a method that combines
various approaches to extract social networks. Especially, three kinds of
networks are extracted: user-registered Know-link networks; Web-mined
Web-link networks; and face-to-face Touch-link networks. This paper
describes the combination of social network extraction for an eventparticipant community. Analyses on the extracted social networks arealso presented.

1

Introduction

This paper presents an integrated method for social network extraction. Social
networks play important roles in our daily lives. Social networks overwhelmingly
influence our lives without our knowledge of their implications. Many applications use social networks [12]. In the context of the Semantic Web, social
networks are crucial to realize a web of trust, which enables the estimation of
information credibility and trustworthiness [3][6]. Ontology construction is also
related to social networks [9].
People pay attention to social networks not only for academic study, but also
for commercial services. Social networking services (SNSs) have become popular. Friendster 3 and Orkut 4 are among the earliest and most successful SNSs.
An interesting aspect of SNSs is that a users can visualize social networks (acquaintance lists) in addition to others’ personal attributes (e.g., name, affiliation,
hobby). Acquaintance lists reveal information about users’ personalities. On theother hand, acquaintance lists are proof that acquaintances can track activity
within the SNS. We can expect that the purview of acquaintances that such lists
offer serves to restrict anti-social behavior within a community (e.g., assuming
false names, abusive language). In fact, a famous Japanese SNS called mixi 53

http://www.friendster.com/
https://www.orkut.com/
5
http://mixi.jp/
4

2

has three million users; 70% of them are active users. In all, mixi has 490,000
communities (BBS), but maintaining communications on online communities
presents some difficulties [4]. An SNS that manages and stores social networks
can become a base of our future information infrastructure.
Currently, we are doing an Event Space Information Support Project. We havetargeted event spaces such as expositions or conventions because such events
involve rich contents and many attendees. This project is intended to activate
the community by supporting real-world-based interaction using Ubiquitous andSemantic Web technologies. Ishida [5] explained that community computing includes five functions for encouraging social interaction in communities: knowing
each other, sharing preferences and knowledge, generating consensus, supporting
everyday life, and assisting social events. We try to realize such functions usingsocial networks.
What is a difference between an ordinary SNS and an SNS for an event
participants’ community? All SNS users use SNS. Nevertheless, not every event
participant uses it. Furthermore event participants’ communities have alreadyhad social networks and are created in event spaces and other places. Our necessary SNS should reflect actual social networks in that community. It requires amethod to obtain social networks not only from user registration but also others.
We called this challenge Community Focused Social Network Extraction.
We propose a new method to extract social networks. It is a combination of
three methods. We targeted an academic conference as the first trial community
for our proposed method and developed a system that has our proposed method.
We operated our system at some academic conferences. We have analyzed theirrespective social networks. This paper describes characteristics of three means of
extraction of social networks and discusses the effectiveness of their combination.

2

Community Focused Social Network Extraction

2.1

Approach of Social Network Extraction

This section presents a summary of methods to obtain social networks. Several
means exist to obtain social networks: Friend-of-a-Friend (FOAF) is a vocabulary
to describe information on a person and their relation to others. We can collect
FOAF files and obtain a FOAF network [2][8]. Users create both SNS data and
FOAF data themselves.
On the other hand, automatic detection of relations is also possible fromvarious sources of online information such as e-mail archives, schedule data, andWeb citation information [1][14][10]. Especially in some works, social networks
are extracted by measuring the co-occurrence of names on the Web using a searchengine [8][7].
Another means has been explored to obtain social networks: observing persons’ behaviors using ubiquitous and wearable devices [11].
Whichever method is taken for obtaining a social network, it suffers fromsome flaws. For example, SNS data and FOAF data, which are based on selfreporting, suffer from data bias and sparseness. Users might name some of their

3

work acquaintances, but they might not include private friends. Some name hundreds of friends, while others name only a few. People create SNSs data by selecting registered users on the SNS and FOAF data by naming others freely. Sparsity
in FOAF data is more serious than SNSs data. Automatically obtained networks,e.g., Web-mined social networks, provide a good view of prominent persons, butthey do not properly record relationships of novices, students, and other ”normal” people. Social networks observed using wearable devices are constrainedby device-specific characteristics: they might have detection errors, limitation of
detection scopes, and biased usage by users.
2.2

Our Proposed Method

This paper presents a method to extract social networks for a specific community. In this case, we target an academic conference participants’ community. For
extracting social network from a community, it is important to obtain cooperation from community members. For that reason, we infer that it is important tocreate the initial network without demanding personal information input fromthe user to make the whole social network useful [13]. The initial network should
be modified according to user interaction to the system. For example, the initial information from the user is from the web system that has a click button
to show that a user knows this person or is interested in some content, which
preference might resemble the preferences of other users. Such information fromweb systems is added to the social network. Real-world-based user interaction
information is also added, e.g., if three users used the same table together andthe same demonstration was visited simultaneously by two other users.
Figure 1 shows our proposed methods. Ordinarily, a user registers a social
network (1) in an SNS. We have proposed methods to extract social networks
using user interaction (2) and web mining (3). Conventional methods cannot
extract social networks among a community automatically and improve themusing user-system interactions. We proposed a combined social network extraction method that includes many web services based on community interests andcontents and onsite systems that have been deployed in real-world space forsupporting mobile users in the site.

3

POLYPHONET Conference

We developed POLYPHONET Conference (hereafter, POLYPHONET) that has
our proposed method. The system is a community support system whose target
is an academic conference.
POLYPHONET Conference has functions as a social networking service anda conference scheduling system. A user can find research topics that a researcher
is exploring or with whom she is working. In the scheduling part, a user canregister interesting presentations (papers, demos and posters)
Our proposed method thereby comprises three means to extract social networks. The first is based on web mining techniques. This method can create initial networks automatically from available web information. The second is based

4Fig. 1. Proposed Method

on real-world-based user interaction in communities. Furthermore, the method
captures user interactions in the conference room. The last is based on user interaction on the web system. It gathers user clicks of acquaintance buttons: it
is similar to SNS. We call the first a Web-link and the second a Touch-link; thelast is a Know-link.
A Web-link is extracted from the Web using Web Mining techniques. We
applied the web mining method based on method [7] to extract a social network
among participants. That method is based on measuring the relevance of two
nodes based on the number of retrieved results obtained by a search engine query.
Users register a Touch-link via an information kiosk. We set several information kiosk in an public space and deliver each participant an ID card as a namecard (Figure 2-b). They can log in to POLYPHONET directly when a single
participant puts an ID card on the card reader. They can view social networks
among them and compare personal schedule if two or three participants place
ID cards there together. Then the social-tie ”We meet and see social networks
together” is added to POLYPHONET automatically. It seemed to provide easy
and a good balance between privacy and effectiveness because user understands
how and to whom the relation will be created.
Users on the web system can register a Know-link. A user can make an
addition to the ”I-know” list when that user finds an acquaintance. At thattime, the acquaintance is also added to the acquaintance’s ”I’m-known-by” list.
The system has a portal page that is tailored to an individual user, called
my page. The user’s presentations, bookmarks of presentations, and registeredacquaintances are shown along with the social network extracted from the Web.
It helps users to register Knows-link easily by seeing the Web-links.

5Fig. 2. Information Kiosk and ID Card Fig. 3. Two Users at an Information
Kiosk.

4

Field Test

We tested our system at 17th, 18th and 19th Annual Conferences of the Japan
Society of Artificial Intelligence (JSAI2003, JSAI2004, and JSAI2005) and at
The International Conference on Ubiquitous Computing (UbiComp 2005) andanalyzed obtained social networks. In this paper, we show some results of analyses on obtained networks from JSAI2005.
That conference included 297 presentations and 579 authors (including coauthors). About 500 participants joined that conference: its size was similar tothat of a conference at which we tested the previous system. The system started
at 5th June. In all, our system’s users were 217.
POLYPHONET extracts social networks among participants using threemethods. First, the system extracts them using Web mining technique as initial data (Web-link). Second, users can register their own social networks with
our system (Know-link). Third, two or three users can register their face-to-facemeeting through information kiosks (Touch-link).
As a result, Web-link has 484 nodes and 34,880 links. Touch-link has 162
nodes and 288 links. And Know-link has 94 nodes and 1,326 links. Web-links are
more numerous than others, which serves our system well. It uses Web-links asinitial data of social networks. It is therefore desirable that every user has initial
personal data. The number of users of Touch-link is larger than Know-link eventhough users can create Touch-link for only three days. It indicates Touch-link
can provide an easy way to register social networks for community members.
About half of the Know-links are common with Web-links, indicating theinitial network validity. From user log analysis, 52% of the Know-links are registered from a user’s Web-links page. This suggest that at least in POLYPHONET,the Web-link contributes to set Know-links efficiently.

6Fig. 4. Ration of Link Users at JSAI2005. ’Know-Link’ means users who have undirected Know link and ’Add Know-Link’ means users who added Know link.

Figure 4 shows the number of Web hit (by putting a person’s name to asearch engine) versus the number of three kinds of links. The more authoritative
people (with lots of hit count) tend to have more number of Web links. While
the most authoritative people do not use Knows links the most; active middleauthoritative users use the most. They may know well about the community,and feel interesting. Touch links are used by the less authoritative users more;
especially, the persons with the same level of authoritativeness are likely to havemeets link. It is natural because persons who have fewer acquaintances wantmore acquaintances, and people are likely to meets people with the same social
level.
Community focused social network extraction should reflect social network ofa target community. Our target community is participants of an academic conference and it has various members. Results of this field-test shows our proposed
method extracts social network from such various members.
Every Web-link, Touch-link, and Know-link has own characteristic even though
they mean same social relationship. When we make applications with three links,
we should improve a way to integrate them for each application. For example,
Web-link is more effective when we use social network as context like a presentation page in POLYPHONET because Web-link can cover relationship ofauthoritative people. When we use social network for communication support, it
seems that Touch-link and Know-link is more effective because they are createdby active users. Especially, Touch-link is a key because actually a person meetsothers on site, the person feel easy talking again to introduce someone.

5

Conclusion

This paper presents community-focused social networks and extraction methods. We implemented our proposed method to POLYPHONET Conference andapplied it to the academic conference. Results of field-testing show that our proposed method can realize unbiased extraction of social networks and provide a
simple means to register social networks for users.
Community Focused Social Network Extraction is important for using SNS
as an information infrastructure of one community. Social network is related to7

Semantic Web technology. If SNS is approved as an information infrastructure,
the achievement of advanced information support by Semantic Web technology
becomes possible, too. I hope this research becomes the help. Future studies willaddress network integration methods, especially how to integrate various kinds ofedges, and novel applications using social networks for supporting communities.

6

Acknowledgments

This research has been supported by NEDO (New Energy and Industrial Technology Development Organization) as the project ID of 04A11502a.

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