Mapping Science - Mapping Scientific Frontiers: The Quest for Knowledge Visualization - page 257

of peripheral clusters and the continuous growth of the core clusters. Finally,
the core clusters' growth becomes predominant again. Buter et al. ( 2011 ) studied
the emergence of an interdisciplinary research area from fields that did not show
interdisciplinary connections before. They used journal subject categories as a proxy
for fields and citations as a measure of interdisciplinary connection.
Lahiri et al. addressed how structural changes of a network may influence the
spread of information over the network (Lahiri et al. 2008 ). Although they did not
study bibliographic networks per se, their study indicates predictions made about
how information spreads over a network are sensitive to structural changes of the
network. This observation underlines the importance of taking structural change into
account in the development of metrics based on topological properties of networks.
Leydesdorff ( 2001 ) raised questions (p. 146) that are closely related to what we
are addressing: “How does the new text link up to the literature, and what is its
impact on the network of previously existing relations?” He took a quite different
approach and analyzed word occurrences in scientific papers from an information-
theoretic perspective. In his approach, the publication of a paper is perceived as an
event that may lead to the reduction of uncertainty involved in the current state of
knowledge. He devised diagrams that depict pathways of how a particular paper
improves the efficiency of communication. Although the information-theoretic
approach and our structural variation approach currently operate on different units of
analysis with distinct theoretical underpinnings, both share the fundamental concern
of changes introduced by newly published scientific papers on the existing body of
knowledge.
As shown above, many studies in the literature have addressed factors that may
influence citations. The value of our work is the introduction of the structural
variation paradigm along with computational metrics that can be integrated into in-
teractive exploration systems to better understand precisely the impact of individual
links made by a new article.

8.1.2 A Structural Variation Model

There is a recurring theme from a diverse body of work on creativity. A major
form of creative work is to bridge previously disjoint bodies of knowledge. Notable
studies include the work of Ronald S. Burt in sociology (Burt 2004 ), Donald
Swanson in information science (Swanson 1986a ), and conceptual blending as a
theoretical framework for exploring human information integration (Fauconnier and
Turner 1998 ). We have been developing an explanatory and computational theory
of transformative discovery based on criteria derived from structural and temporal
properties (Chen 2011 ;Chenetal. 2009 ).
In the history of science, there are many examples of how new theories revolu-
tionized the contemporary knowledge structure. For example, the 2005 Nobel Prize
in medicine was awarded to the discovery of Helicobacter pylori , a bacterium which
was not believed to be possible to find in human's gastric system (Chen et al. 2009 ).