1,720,960 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Effiziente visuelle Navigation in hierarchisch strukturierten Graphen
Get PDFVisual navigation of hierarchically structured graphs is a technique for interactively exploring large graphs that possess an additional hierarchical structure. This structure is expressed in form of a recursive clustering of the nodes: in call graphs of telephone networks, for instance, the nodes are identified with phone numbers; they are clustered recursively through the implicit structure of the numbers, e. g., nodes with the same area code belong to a cluster. In order to reduce the complexity and the size of the graph, only those subgraphs that are currently needed are shown in detail, while the others are collapsed, i. e., represented by meta nodes. In such a graph view the subgraphs in the areas of interest are expanded furthest, whereas those on the periphery are abstracted. As the areas of interest change over time, clusters in a view need to be expanded or contracted. First and foremost, there is need for an efficient data structure for this graph view maintenance problem. Depending on the admissible modifications of the graph and its hierarchical clustering, three variants have been discussed in the literature: in the static case, everything is fixed; in the dynamic graph variant, only edges of the graph can be inserted and deleted; finally, in the dynamic graph and tree variant the graph additionally is subject to node insertions and deletions and the clustering may change through splitting and merging of clusters. We introduce a new variant, dynamic leaves, which is based on the dynamic graph variant, but additionally allows insertion and deletion of graph nodes, i. e., leaves of the hierarchy. So far efficient data structures were known only for the static and the dynamic graph variant, i. e., neither the nodes of the graph nor the clustering could be modified. As this is unsatisfactory in an interactive editor for hierarchically structured graphs, we first generalize the approach of Buchsbaum et. al (Proc. 8th ESA, vol. 1879 of LNCS, pp. 120–131, 2000), in which graph view maintenance is formulated as a special case of range searching over tree cross products, to the new dynamic leaves variant. This generalization builds on a novel technique of superimposing a search tree over an ordered list maintenance structure. With an additional factor of roughly O(log n/log log n), this is the first data structure for the problem of graph view maintenance where the node set is dynamic. Visualizing the expanding and contracting appropriately is the second challenge. We propose a local update scheme for the algorithm of Sugiyama and Misue (IEEE Trans. on Systems, Man, and Cybernetics 21 (1991) 876– 892) for drawing compound digraphs. The layered drawings that it produces have many applications ranging from biochemical pathways to UML diagrams. Modifying the intermediate results of every step of the original algorithm locally, the update scheme is more efficient than re-applying the entire algorithm after expansion or contraction. As our experimental results on randomly generated graphs show, the average time for updating the drawing is around 50 % of the time for redrawing for dense graphs and below 20 % for sparse graphs. Also, the performance gain is not at the expense of quality as regards the area of the drawing, which increases only insignificantly, and the number of crossings, which is reduced. At the same time, the locality of the updates preserves the user ’s mental map of the graph: nodes that are are not affected stay on the same level in the same relative order and expanded edges take the same course as the corresponding contracted edge; furthermore, expansion and contraction are visually inverse. Finally, our new data structure and the update scheme are combined into an interactive editor and viewer for compound (di-)graphs. A flexible and extensible software architecture is introduced that lays the ground for future research. It employs the well-known Model-View-Controller (MVC) paradigm to separate the abstract data from its presentation. As a consequence, the purely combinatorial parts, i. e., the compound (di-)graph and its views, are reusable without the editor front-end. A proof-of-concept implementation based on the proposed architecture shows its feasibility and suitability
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Open Problems Wiki
No full textThis project was inspired by the last year's paper on Selected Open Problems in Graph Drawing by Brandenburg et al. (Proc. 11th GD. Vol. 2919 of LNCS. (2003) 515–539). While being a very good start, a paper is inherently static and will become out-dated. For dynamic content, what open problems (hopefully) are, a web-site is more appropriate. Keeping such a site up-to-date, however, is time consuming and requires good knowledge of recent work. In projects like the free encyclopedia Wikipedia these obstacles are overcome with a collaborative approach: everyone is allowed, and even requested, to contribute his knowledge to the site. The Open Problems Wiki makes use of this paradigm to provide a forum for collecting open problems in graph drawing
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
HGV: A Library for Hierarchies, Graphs, and Views
No full textWe introduce the base architecture of a software library which combines graphs, hierarchies, and views and describes the interactions between them. Each graph may have arbitrarily many hierarchies and each hierarchy may have arbitrarily many views. Both the hierarchies and the views can be added and removed dynamically from the corresponding graph and hierarchy, respectively. The software library shall serve as a platform for algorithms and data structures on hierarchically structured graphs. Such graphs become increasingly important and occur in special applications, e. g., call graphs in software engineering or biochemical pathways, with a particular need to manipulate and draw graphs
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