During the last years, constructive approximation has reached out to enc- pass the computational and approximation-theoretical aspects of di?erent ?elds in applied mathematics, including multivariate approximation methods, qua- interpolation, and multivariate approximation by (orthogonal) polynomials, as well as modern mathematical developments in neuro fuzzy approximation, R- networks, industrial and engineering applications. Following the tradition of our internationalBommerholz conferencesin 1995, 1998, and 2001 we regard this 4th IBoMAT meeting as an important possibility for specialists in the ?eld of applied mathematics to communicateabout new ideas with colleaguesfrom 15 di?erent countries all over Europe and as far awayas New Zealand and the U.S.A. The conference in Witten Bommerholz was, as always, held in a very friendly and congenial atmosphere. The IBoMAT-series editor Detlef H. Mache (Bochum) would like to congr- ulate Marcel de Bruin (Delft) and Joz ´ sef Szabados (Budapest) for an excellent editing job of this 4th volume about Trends and Applications in constructive - proximation. After the previous three published books in Akademie Verlag (1995) and Birkh¨ auser Verlag (1999 and 2003) we were pleased with the high quality of the contributions which could be solicited for the book. They are refereed and we should mention our gratitude to the referees and their reports.