  The aggregated citation relations among journals included in the Science
Citation Index provide us with a huge matrix which can be analyzed in various
ways. Using principal component analysis or factor analysis, the factor scores
can be used as indicators of the position of the cited journals in the citing
dimensions of the database. Unrotated factor scores are exact, and the
extraction of principal components can be made stepwise since the principal
components are independent. Rotation may be needed for the designation, but in
the rotated solution a model is assumed. This assumption can be legitimated on
pragmatic or theoretical grounds. Since the resulting outcomes remain sensitive
to the assumptions in the model, an unambiguous classification is no longer
possible in this case. However, the factor-analytic solutions allow us to test
classifications against the structures contained in the database. This will be
demonstrated for the delineation of a set of biochemistry journals.
