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This book constitutes the refereed proceedings of the Second International Workshop on Experimental and Efficient Algorithms, WEA 2003, held in Ascona, Switzerland in May 2003. The 19 revised full papers presented together with 3 invited contributions were carefully reviewed and selected from 40 submissions. The focus of the volume is on applications of efficient algorithms for combinatorial problems.

This book collects selected contributions presented at the INdAM Workshop'Geometric Challenges in Isogeometric Analysis', held in Rome, Italy on January 27-31, 2020. It gives an overview of the forefront research on splines and their efficient use in isogeometric methods for the discretization of differential problems over complex and trimmed geometries. A variety of research topics in this context are covered, including (i) high-quality spline surfaces on complex and trimmed geometries, (ii) construction and analysis of smooth spline spaces on unstructured meshes, (iii) numerical aspects and benchmarking of isogeometric discretizations on unstructured meshes, meshing strategies and software. Given its scope, the book will be of interest to both researchers and graduate students working in the areas of approximation theory, geometric design and numerical simulation.Chapter 10 is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.

During the last three decades several different styles of semantics for program­ ming languages have been developed. This book compares two of them: the operational and the denotational approach. On the basis of several exam­ ples we show how to define operational and denotational semantic models for programming languages. Furthermore, we introduce a general technique for comparing various semantic models for a given language. We focus on different degrees of nondeterminism in programming lan­ guages. Nondeterminism arises naturally in concurrent languages. It is also an important concept in specification languages. In the examples discussed, the degree of non determinism ranges from a choice between two alternatives to a choice between a collection of alternatives indexed by a closed interval of the real numbers. The former arises in a language with nondeterministic choices. A real time language with dense choices gives rise to the latter. We also consider the nondeterministic random assignment and parallel composition, both couched in a simple language. Besides non determinism our four example languages contain some form of recursion, a key ingredient of programming languages.