Questo glossario intende fornire delle definizioni sintetiche di keyword tecniche molto specifiche contenute nella Base di Dati. Le definizioni sono tratte da siti specialistici.
Si rimanda, per ulteriori approfondimenti, agli articoli indicizzati secondo tali keyword e alle loro Note ed URL.
Bradford's Law*
Bradford's Law serves as a general guideline to librarians in determining the number of core journals in any given field. It states that journals in a single field can be divided into three parts, each containing the same number of articles: 1) a core of journals on the subject, relatively few in number, that produces approximately one-third of all the articles, 2) a second zone, containing the same number of articles as the first, but a greater number of journals, and 3) a third zone, containing the same number of articles as the second, but a still greater number of journals. The mathematical relationship of the number of journals in the core to the first zone is a constant n and to the second zone the relationship is n². Bradford expressed this relationship as 1:n:n². Bradford formulated his law after studying a bibliography of geophysics, covering 326 journals in the field. He discovered that 9 journals contained 429 articles, 59 contained 499 articles, and 258 contained 404 articles. So it took 9 journals to contribute one-third of the articles, 5 times 9, or 45, to produce the next third, and 5 times 5 times 9, or 225, to produce the last third. As may be seen, Bradford's Law is not statistically accurate, strictly speaking. But it is still commonly used as a general rule of thumb (Potter 1988).
Lotka's Law*
Lotka's Law describes the frequency of publication by authors in a given field. It states that " . . . the number (of authors) making n contributions is about 1/n² of those making one; and the proportion of all contributors, that make a single contribution, is about 60 percent" (Lotka 1926, cited in Potter 1988). This means that out of all the authors in a given field, 60 percent will have just one publication, and 15 percent will have two publications, 7 percent of authors will have three publications, and so on.
In brief:
% of authors with 1 publication = 60%
% of authors with 2 publications (1/2² x 60)= 15%
% of authors with 3 publications (1/3² x 60)= 7%
% of authors with 7+ publications (1/7+² x 60)>=6%
According to Lotka's Law of scientific productivity, only six percent of the authors in a field will produce more than 10 articles. Lotka's Law, when applied to large bodies of literature over a fairly long period of time, can be accurate in general, but not statistically exact. It is often used to estimate the frequency with which authors will appear in an online catalog (Potter 1988).
Zipf's Law*
Zipf's Law is often used to predict the frequency of words within a text. The Law states that in a relatively lengthy text, if you "list the words occurring within that text in order of decreasing frequency, the rank of a word on that list multiplied by its frequency will equal a constant. The equation for this relationship is: r x f = k where r is the rank of the word, f is the frequency, and k is the constant (Potter 1988). Zipf illustrated his law with an analysis of James Joyce's Ulysses.
"He showed that the tenth most frequent word occurred 2,653 times, the hundredth most frequent word occurred 265 times, the two hundredth word occurred 133 times, and so on. Zipf found, then that the rank of the word multiplied by the frequency of the word equals a constant that is approximately 26,500" (Potter 1988). Zipf's Law, again, is not statistically perfect, but it is very useful for indexers.
* Informazioni tratte dai siti della School of Information, University of Texas, USA e del Library and Information Science Program College of Education, University of Denver, USA.
Data Envelopment Analysis (DEA)
Data Envelopment Analysis (DEA) is a tool, a technique, used to construct relative scientific and technological indicators. It allows to compare the values of one specific indicator of each "unit of analysis" (institutions, governments, research groups etc.).
Matthew Effect
According to Merton (1968), "the Matthew effect consists of the accruing of greater increments of recognition for particular scientific contributions to scientists of considerable repute and the withholding of such recognition from scientists who have not yet made their mark". Merton saw this effect in the careers of some of the scientists he studied; when they started out, they had trouble getting credit for discoveries, especially if one of their collaborators was an eminent scientist. Later in their careers, after they had established their reputation, the reverse happened--they received credit for work done by junior collaborators, even when they tried to share. A classic case is the discovery of penicillin. In most accounts, Alexander Fleming is given virtually all the credit, but the actual refinement of this mold into a powerful antibiotic was due to Howard Florey, Ernst Chain and others.
Research Assessment Exercise (RAE)
The Research Assessment Exercise (RAE) is run every four years in the UK by the Higher Education Funding Councils. The aim of the exercise is to measure research activity in British academic institutions and thus determine how the councils' research budget will be distributed among the country's universities.
Roy approximation
Roy approximation refers to a formula he designed for computing total citation counts:
CT=CF x TP/FP
where
CT=total citation count
CF=citations to primary author papers
TP= total number of papers
FP=number of primary author papers
Roy argued that the use of this formula would eliminate the need to compile citation data on secondary authors to make comparison. The formula has yet been criticised since early '80s.
Graph theory analysis, Indexing model, Lattice theory, Lerch zeta function, Metric model, Nonlinear equation systems,
Neural network, Power law distribution, Scale-independent properties, Scaling method
Per questo gruppo di keyword, che si riferiscono a teorie, modelli e sistemi di derivazione matematico-statistica, si rimanda agli articoli con esse indicizzati e alle loro eventuali Note e URL.