Fast and reliable predictions on atomic data are needed in many fields of physics.
In astro and plasma physics, for instance, they often provide the input basis for
subsequent models in order to understand the behaviour of atoms and ions over a
wide range of (plasma) densities. Until now, however, the accurate prediction of
such data still remains much as a challenge owing to the complexity of most atoms
and because of the large variety of the required data. For many configurations,
in particular, difficulties arise from the open-shell structure and from the fact that
not only correlations among the electrons but also 'elativistic effects' must be
treated properly for medium and high nuclear charges and if inner--shell electrons
become involved in the atomic processes.

But despite of these difficulties with 'open shells', there have been some
remarkable achievements during the last decade which cannot be attributed purely
to the enhancement of the available computer ressources. Of rather equal
importance appears the development of new computational methods and program
tools which are suitable for large- scale applications. In this contribution, therefore,
I will survey and discuss the capabilities of present-day relativistic structure
calculations for open-shell atoms and ions, compared with standard computations
and the practical needs. Emphasis is placed on the features and successes of the
currently available relativistic atomic structure codes such as GRASP92 [1] or
RATIP [2] for calculating (relativistic atomic) transition and ionization properties.

The present form of the RATIP program supports computations on a variety of
properties, including the interaction of atoms with the radiation field and with
electrons in the continuum. Detailed investigations can be carried out for Einstein
coefficients, branching ratios, lifetimes as well as Auger intensities and angular
distribution parameters. Recently, moreover, much emphasize was paid to the
study of the radiative and dielectronic capture of electrons as well as to their
impact excitation. A series of large-scale computations on the optical spectra
and lifetimes showed, in particular, that accurate predictions are possible today
even for open-shell ions if the effects of relativity and many- particle correlations
are treated consistently on the same theoretical basis [3].

References