This paper analyzes the centrality of the Delicious social bookmarking system as it relates to the globalization of agriculture, highlighting how network centralization and public recognition affect hyperlink formation. The study employed social network analysis to reveal that a small number of authoritative websites dominate in terms of the number of inbound links, illustrating the principle of the Zipf law in the network. The findings indicate that the bookmarking practices reflect user preferences and political influences, with implications for understanding online social dynamics and potential applications in various fields such as advertising and social movements.

1. 1
Hyperlink Formation in Social Bookmarking Systems:
Who is Who Online?
1st European Conference
on Social Networks (EUSN)
1-4 July 2014, Barcelona, Spain
http://www.eusn.org
Juan D. Borrero, jdiego@uhu.es
Estrella Gualda, estrella@uhu.es
José Carpio, jose.carpio@dti.uhu.es
University of Huelva, Spain

2. 2
Why this paper?
Network centrality
 High centrality is a property of large networks
like on the Internet (Barabási and Réka, 1999;
Barabási et al., 2000).
 The Zipf/power law is a defining characteristic
of large-scale networks such as the Web (e.g.
Barabási and Réka, 1999), which implies a high
degree of network centralization.
 It is unclear whether this is also a feature of the
properties of sub-networks.

3. 3
Why this paper?
Node centrality and preferences
 The Web links are of
conferrers of “authority”
(Kleinberg, 1999) or
“endorsement” (Davenport
and Cronin, 2000) and can
indicate preferences (see
Baldassarri and Diani, 2007).
 We argue that te prominence
of a website, as measured by
its status or public
recognition, also determines
its centrality.
 Little literature has in
account implicit relations
between nodes within online
networks (e.g., Ackland and
O’Neil, 2011).
 The ties among websites
bookmarked can indicate
preferences.

4. 4
Why this paper?
Social Bookmarking
 Provides a huge amount of
user-generated annotations
for web content.
 Reflects the interests of
millions of users.
 Collective knowledge
(Wisdom-of-crowds).
 Research areas: (Web-)
Search & Content
classification, Ontology
building, Trend detection,
Recommendation, Sociology
…
Source: http://blog.hubspot.com/blog/tabid/6307/bid/7372/9-Reasons-Why-
Your-Social-Media-Strategy-Isn-t-Working.aspx/

5. 5
Hyperlink Formation in Social Bookmarking Systems: Who is Who Online?
Context and Topic of Study
Delicious
Delicious as a hyperlink network
Globalization of Agriculture
Objectives and Hypotheses
Methodology
Data collection
Analysis
Results
Network centralization
Top authoritative nodes
Visualization network
Discussion and Conclusions
Further Research
Possible Applications
Outline

6. 6
Context and Topic of Study
Delicious
A free social bookmarking web service for storing, sharing and discovering web
bookmarks

7. 7
Context and Topic of Study
Delicious
Collective nature
• Content is created, annotated and viewed by its users.
• Users can tag each of their bookmarks on the Delicious website, and provides
knowledge about the URL marked.
• View bookmarks added or annotated by other users

8. 8
Context and Topic of Study
Delicious as a hyperlink network
The structure of Social tagging –Delicious- website can be viewed as a
network of three different and interconnected node types (tripartite
network): the user who make the annotation, the link to the resource
(urls) and one or more tags.
we see the hyperlink network (uurl)
we can also see indirected links (e.g.
between urls - straight lines), that represent
a unipartite network
u
u’
u’’
url
url’
url’’
T’’’
T’’
T’
T

9. 9
Context and Topic of Study
Topic
Globalization
Implies large market as result of the reduction transaction costs of international
trade
implications
Globalization of agriculture
- trade (foods, goods)
- prices (food, goods)
- food consumption (bulk products versus processed products)
- R&D
- rules and laws (subsidies, WTO related to poverty)
effects
Asymmetries
more easily
Discussion/diffusion Web 2.0

10. 10
Objectives and Hypotheses
1. To analize the delicious sub-network centrality
2. To link node centrality with public recognition
3. To discover implicit relations between urls

11. 11
Objectives and Hypotheses
1. To analize the delicious sub-network centrality
H1: In the globalization of agriculture network on
delicious (sub-network) Zipf law is fulfilled.
2. To link node centrality with public recognition
H2: Websites with a higher public recognition will be
more likely to receive a large number of links
3. To discover implicit relations between urls
H3: The ties among urls can indicate preferences

12. 12
Methodology
Data collection
(A) Start point. Identify the search
attributes. Authoritative source as
baseline to find keywords
connected to the idea of
‘globalization of agriculture’
(B) Perl program web-crawling was
made to gather the sample of users,
URLs and tags from 22 April 2011 to
21 May 2011.
(C) Results 3,668 users on 4,913
URLs.
(D) Program in Haskell to reduce
the amount of data by cutting the
URLs.

13. 13
Methodology
Analysis
Social Network Analysis (SNA) with Pajek and
Gephi software,
1.studying the properties of centrality
2.visualizing through graphs.

14. Results
H1: Network centralization
Hyperlink Network (userURL). The degree of variability in URL centrality scores according to indegree.
14
2,148 URLs arranged in rank order by number of
inbound links (URL’s Indegree: Sum of total inbound
links)
Only 10 URLs from 2,148 (0.47%) account for 17.97% of links.
1% URLs (22 URLs from 2,148) account for 26.50% of links.
Zipf law
The network is highly centralized within a few nodes.
How come that a few websites receive more links?

15. Results
H2: Top authoritative nodes in the Delicious “Globalization of agriculture” hyperlink
network (userURL)
Ten most
centralized
websites
15
Six of them were
well-know media-based
(online
newspapers) and
activists
Indegree
Value URL Description
1 259 www.nytimes.com Online newspaper
2 170 www.independent.co.uk Online newspaper
3 155 www.naomiklein.org Activist media site
4 144 www.news.bbc.co.uk/ Online newspaper
5 124 www.globalresearch.ca Activist media site
6 95 www.spiegel.de/ Online newspaper
7 94 www.guardian.co.uk/ Online newspaper
8 94 www.economist.com/ Online newspaper
9 87 www.corpwatch.org Activist media site
10 172 www.theatlantic.com Online magazine
Alexa.com
130
568
1,010,476
63
10,795
170
14,493
1,747
335,338
1,063
www.uab.cat 29,555 The popularity of the website
bookmarked determines its centrality

16. 16
Results
H2: Top authoritative nodes in unipartite network (URL-URL)
Ties based on preferences at bookmarking URLs
Ten most centralized websites
Degree Closeness Betweenness
1 537 www.nytimes.com 0.4421 www.nytimes.com 0.0930 www.nytimes.com
2 386 www.news.bbc.co.uk 0.4180 www.news.bbc.co.uk 0.0593 www.news.bbc.co.uk
3 337 www.economist.com 0.4068 www.guardian.co.uk 0.0366 www.globalresearch.ca
4 324 www.guardian.co.uk 0.3992 www.economist.com 0.0341 www.guardian.co.uk
5 286 www.ft.com 0.3886 www.rodrik.typepad.com 0.0293 www.naomiklein.org
6 257 www.rodrik.typepad.com 0.3868 www.ft.com 0.0290 www.economist.com
7 243 www.en.wikipedia.org 0.3854 www.en.wikipedia.org 0.0262 www.wikipedia.org
8 222 www.youtube.com 0.3820 www.spiegel.de 0.0207 www.youtube.com
9 218 www.spiegel.de 0.3814 www.washingtonpost.com 0.0191 www.spiegel.de
10 217 www.globalresearch.ca 0.3800 www.globalresearch.ca 0.0184 www.ft.com
Again the majority were well-know media-based (online
newspapers) and Web 2.0 (YouTube and Wikipedia).
The popularity of the website
bookmarked determines its centrality 3 6
Alexa

17. 17
Results
H3: Visualization URL-URL unipartite network.
Colour: Communities. Layout: ForceAtlas2 from Gephi.
We found two
different
communities
1.the mass
media websites
belong to the
blue one, and
2.the main
activists
websites are
included in the
green cluster
Ties based
on user
preferences
Complete
network
Main
communities
Size: Degree
Size: Betweenness

18. • Very unequal distribution of power of the URLs bookmarked in
the topic globalization of agriculture (O1)
– Most bookmarked URLs seem to reflect preferences of USERs at bookmarking
websites.
– userURL network reflects a big centralization of preferences, and the existence
of long tail.
• Maybe not by chance, main nodes represent authoritative
websites in the world (O2)
– Well know mass media and popular activists surpassed by far other resources
bookmarked.
• The collaborative practice of bookmarking websites in Delicious
can allow us to discover virtual communities (O3)
– URL-URL unipartite network produces clusters of URLs.
– Identification of key collective actors (represented here through URLs) allow a
better comprehension of leadership, influence processes, and power-related
structures.
18
Discussion and conclusions

19. 19
Further research
• Why is ‘that’ so important URL in the network of
globalization of agriculture?
– Key URLs in this type of network could configure and reconfigure the
evolution of the network (TIME), and structure and even manipulate
the type of interchange of resources in Delicious or in similar
bookmarking sites.
• Go in-depth about users.
– To identify of key actors that share URLs.
• Distinction between scientifics and other professionals.
– To distinct users in the way how they use some tags
• Distinction between scientifics / other professionals or users?
• Identify users with the same patterns at tagging, or URLs that were
similarly labelled: study structural equivalences
• Is it by chance? Do the most prominent actors correspond to a profile of very active
and participative people? Do they usually work (or have as hobby) in this area and
this is why tag so many URLs in Delicious?

20. Possible Applications
• Producing and “manipulating” public opinion (at
recommending and describing websites) and markets
20
– If we know the interests of users belonging to a network,
we could also be able to make recommendations
• For social practitioners, is a good way to identify key
informants in a community through which to
disseminate useful and important information.
• Important for researchers interested in formulating
strategies for intervention and mobilization.
• Applications in advertising, e-commerce, social
movements, security…
• …