This was a most unusual and rewarding winter school, and exhausting for lecturers, students and organisers. The organisers are to be congratulated for the excellent planning and running of the school, and the IAC for its vision and courage to choose such a topic, which, at least when it comes to requests for funding, is often claimed to lack merit, and to be regarded as not scientific. The school has clearly proven that scientific expertise is a prerequisite for constructing and maintaining data archives, databases, and WWW interfaces, so as to make them user-friendly and reliable at the same time. Too much effort is often spent on fancy user interfaces, rather than on the content or its adequate documentation in an archive or database.
I have tried to show that more concerted effort is necessary to avoid duplication of similar WWW facilities, and the deterioration of WWW pages with outdated information. Much effort is being spent by individuals, without an institutional support or obligation, in providing useful WWW pages. The advantage is that these are often highly motivated and qualified researchers, but also with the disadvantage that the service will likely be discontinued with personal changes.
I also hope that my lectures will stimulate the use of archives both for advanced research as well as for thesis projects. Nevertheless, the warnings and pointers to possible pitfalls I have tried to strew about my lectures cannot replace a sound observational experience during the first years of research.
Clearly, the educational possibilities of the Internet have not been fully exploited. In fact, this winter school, gathering 50 students in one place and putting them in front of 25 computer terminals, to go and try what they had been taught during the lectures, may have been an interim between a classical school without hands-on exercises and a fully distributed and interactive one, where students would follow lectures over the WWW and perform exercises at home.
I am grateful to the organisers for inviting me to give these lectures, and for their financial support. The persistence and excitement of the students during the practicals was truly impressive. These practicals would have been impossible without the excellent computing facilities prepared for the school by R. Kroll and his team of the ``Centro de Calculo'' of the IAC. I would like to thank the many people who provided useful information, enriching and completing these lecture notes : D. Banhatti, E. Brinks, S. Britzen, J. Burns, J.J. Condon, W.R. Cotton, G. Dulk, W. Erickson, L. Feretti, G. Giovannini, Gopal Krishna, L. Gurvits, S.E.G. Hales, R.W. Hunstead, S. J. Katajainen, K. Kingham, N. Loiseau, V. Migenes, R. Norris, E. Raimond, W. Sherwood, S. A. Trushkin, K. Weiler, and Rick L. White. Thanks also go to all authors of useful WWW pages with compilations of links which I came across while surfing the WWW for this contribution. This paper has made use of NASA's Astrophysics Data System Abstract Service. A. Koekemoer provided help to print Figure 1 successfully, E. Tago kindly helped to produce Figure 6, and special thanks also go to A.C. Davenhall, A. Fletcher, S. Kurtz, and O.B. Slee for their careful reading of the manuscript at the very last moment. All of them strengthened my belief that most of the information given here must have been correct at least at some point in time. Last, but not least, the Editors of this volume are thanked for their eternal patience with the delivery of this report.