Although much has already been achieved, there are clear objectives that need to be met to make further progress in this field. First of all, there is still the need to make detailed modelling of nearby face-on galaxies, both in terms of their integrated SEDs and surface-brightness distributions. Unlike the edge-on geometry, the face-on view also allows the young stellar population and associated dust to be constrained by the morphology of the extincted disk in the UV. Secondly, as already mentioned, we must make the models tractable for application to statistical samples of galaxies, while at the same time retaining their fundamental predictive power. For example, from the perspective of the infrared community, we must provide a viable alternative to Planck curves.
Finally, one would like to impose a physically self-consistent framework on these models, in which the geometry of the stellar populations and of the gas and dust is calculated self-consistently in terms of the gravitational potential of the galaxy.
We would like to thank N.D. Kylafis, M.A. Dopita, A. Misiriotis, M. Xilouris, J. Fischera, B.F. Madore & H.J. Völk for the many discussions and fruitful collaboration we have enjoyed over the last years, without which this paper would not have been possible. N.D. Kylafis is also acknowledged for a critical reading of this manuscript.