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- Author or Editor: L. Leydesdorff x
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Abstract
The theory of autopoiesis, i.e., self-referentiality in the operation of the system, provides us with a production rule for change in the structure of the network. Using information theory, a model system is developed to study the relative likelihood of 
dynamic
transitions: various senses of irreversibility (emergence, and path dependency) are disinguished. A test for path dependency is applied to two sets of empirical data which supposedly reflect historical discontinuities: the budget of theFraunhofer Gesellschaft, and the citation network among AIDS research related journals. The model for the interaction between self-referential developments and goal-referential boundary conditions is further specified, using the example of technological trajectories and selection environments.
Abstract
Clusters of normalized title-words in two sets of patent data in the food-sector (from 1985 and 1989, respectively) are analyzed in terms of their underlying document and word structures. The clusters were generated by using the system LEXIMAPPE of the Paris School of Mines. Both input and output data were kindly made available for validation purposes. Analysis of the data shows that the 
centrality
and the density of the clusters produced by LEXIMAPPE are primarily dependent on the number of word occurrences in the corresponding parts of the input matrix. While the clusters are kept approximately equal in terms of the number of words (with a maximum of 10), they vary widely in terms of the number of word occurrences in the underlying document sets. Centrality and density vary correspondingly. The contribution of the smallest cluster to the reduction of uncertainty in the prediction of the document structure is even smaller than that of 77 (other) single words. In the dynamic analysis, I found significant stability where LEXIMAPPE indicated major changes. However, like every clustering algorithm LEXIMAPPE is based on specific assumptions which may lead to specific results that cannot be simulated by using other methods. Researchers who base their results on LEXIMAPPE should be aware of the peculiarities specific to this system.
Abstract
Measurement of the effectiveness of science policies is analyzed as a multi-level problem. Journal-journal citations are discussed as a potential candidate for a domain beyond the control of policy-makers and authors or research groups and therefore may function as a relatively stable and easily accessible baseline for the 
calibration
of outputs and outcomes of science policy. A method is developed, usingSCPsJCRs which is then applied to the two cases of water pollution and humanisation of labor. This method can also be used as a simple indicator for the development of journal-journal citation patterns over time.
Abstract
The dynamic mapping of science using the data in theScience Citation Index was put on the research agenda of science studies byDe Solla Price in the mid 1960s. Recently, proponents of 
co-citation cluster analysis
have claimed that in principle their methodology makes such mapping possible. The study examines this claim, both methodologically and theoretically, in relation to other means of mapping science. A detailed study of a co-citation map, its core documents' citation patterns and the related journal structures, is presented. At these three levels of possible study of aggregates of citations, an analysis is pursued for the years 1978 to 1984. The many different statistical methods which are in use for the analysis of the respective datamatrices—such as cluster analysis, factor analysis and multidimensional scalling—are assessed with a view to their potential to contribute to a better undérstanding of the dynamics at the different levels in relation to each other. This will lead to some recommendations about methods to use and to avoid when we aim at a comprehensive mapping of science. Although the study is pursued at a formal and analytical level, in the conclusions an attempt is made to reflect on the results in terms of further substantial questions for the study of the dynamics of science.
Abstract
With respect to the issue of whether the scientometric measurement of 
the decline of British science
is an artifact of the specific database and underlying assumptions in methods, I argue that there are fewer analytical objections against measurement by usingSciSearch Online than against other methods (based on the fixed journal set and fractional counting). The measurement of international co-authorship, i.e. a network indicator, should not be confounded with measurement of performance of a single nation. The time series for the different subsets of UK-publications, which have been proposed, are given. None of the indicators can be shown to exhibit a trend (in contrast to a drift). The hypothesis of a decline has therefore to be rejected.
The relations between qualitative theory and scientometric methods in science and technology studies
Introduction to the topical issue
Abstract
This issue ofScientometrics originated from a Workshop of the European Association for the Study of Science and Technology (EASST). In this introduction the relations between qualitative theory and the use of scientometric methods is placed in the historical perspective of the emergence of science and technology studies over the last decades. The differences among various theories in terms of dimensions, units of analysis and levels of aggregation are elaborated. Thereafter, the various contributions to the issue are discussed within this framework.
Abstract
A debate has occurred recently over the issue whether it is possible to account for differences in results when using various versions of theScience Citation Index for the measurement of national performance in terms of numbers of scientific publications. This article provides an overview of the various arguments which have been made, and reports that recent reorganization in the on-line installations (SciSearch) should make it possible to circumvene one of the major sources of error.
Abstract
In a series of two articles, I will show that the expected information content of distributions provides us with a straightforward means to develop a static and a dynamic model for the development of the sciences. In the first study, I analyze how knowledge about one indicator (nominal variable) can reduce our uncertainty in the prediction of other indicators, and how relations across various levels of aggregation can be assessed. In the second study, I will address the problem of the use of indicators and relations among them for predictions and reconstructions.I will use the occurrences of words in texts as the prime nominal variable which can be easily counted by the machine. However, I will generalize the models for the multi-variate case, in which any indicator or nominal variable can be assessed in terms of its validity in relation to other indicators and its value for predictions.
