## Fachbereich Informatik

- Data-procedural Languages for FPL-based Machines (1995)
- This paper introduces a new high Level programming language for a novel class of computational devices namely data-procedural machines. These machines are by up to several orders of magnitude more efficient than the von Neumann paradigm of computers and are as flexible and as universal as computers. Their efficiency and flexibility is achieved by using field-programmable logic as the essential technology platform. The paper briefly summarizes and illustrates the essential new features of this language by means of two example programs.

- A graphical representation schema for the software process modeling language MVP-L (1995)
- Experience gathered from applying the software process modeling language MVP-L in software development organizations has shown the need for graphical representations of process models. Project members (i.e„ non MVP-L specialists) review models much more easily by using graphical representations. Although several various graphical notations were developed for individual projects in which MVP-L was applied, there was previously no consistent definition of a mapping between textual MVP-L models and graphical representations. This report defines a graphical representation schema for MVP-L descriptions and combines previous results in a unified form. A basic set of building blocks (i.e., graphical symbols and text fragments) is defined, but because we must first gain experience with the new symbols, only rudimentary guidelines are given for composing basic symbols into a graphical representation of a model.

- MVP-L Language Report Version 2 (1995)
- Intellectual control over software development projects requires the existence of an integrated set of explicit models of the products to be developed, the processes used to develop them, the resources needed, and the productivity and quality aspects involved. In recent years the development of languages, methods and tools for modeling software processes, analyzing and enacting them has become a major emphasis of software engineering research. The majority of current process research concentrates on prescriptive modeling of small, completely formalizable processes and their execution entirely on computers. This research direction has produced process modeling languages suitable for machine rather than human consumption. The MVP project, launched at the University of Maryland and continued at Universität Kaiserslautern, emphasizes building descriptive models of large, real-world processes and their use by humans and computers for the purpose of understanding, analyzing, guiding and improving software development projects. The language MVP-L has been developed with these purposes in mind. In this paper, we motivate the need for MVP-L, introduce the prototype language, and demonstrate its uses. We assume that further improvements to our language will be triggered by lessons learned from applications and experiments.

- The geometry of optimal degree reduction of Bezier curves (1995)
- Optimal degree reductions, i.e. best approximations of \(n\)-th degree Bezier curves by Bezier curves of degree \(n\) - 1, with respect to different norms are studied. It is shown that for any \(L_p\)-norm the euclidean degree reduction where the norm is applied to the euclidean distance function of two curves is identical to componentwise degree reduction. The Bezier points of the degree reductions are found to lie on parallel lines through the Bezier points of any Taylor expansion of degree \(n\) - 1 of the original curve. This geometric situation is shown to hold also in the case of constrained degree reduction. The Bezier points of the degree reduction are explicitly given in the unconstrained case for \(p\) = 1 and \(p\) = 2 and in the constrained case for \(p\) = 2.

- An Optimal Algorithm for the Local Solution of Integral Equations (1995)
- The local solution problem of multivariate Fredholm integral equations is studied. Recent research proved that for several function classes the complexity of this problem is closely related to the Gelfand numbers of some characterizing operators. The generalization of this approach to the situation of arbitrary Banach spaces is the subject of the present paper. Furthermore, an iterative algorithm is described which - under some additional conditions - realizes the optimal error rate. The way these general theorems work is demonstrated by applying them to integral equations in a Sobolev space of periodic functions with dominating mixed derivative of various order.

- Complexity of Multivariate Integral Equations (1995)
- The problem of full solution of Fredholm integral equations of the second kind with data from Sobolev spaces with dominating mixed derivative is studied. Existing estimates for the univariate case are extended to arbitrary dimension.

- Numerical Aspects of Stability Investigations on Surfaces (1995)
- The CAD/CAM-based design of free-form surfaces is the beginning of a chain of operations, which ends with the numerically controlled (NC-) production of the designed object. During this process the shape control is an important step to amount efficiency. Several surface interrogation methods already exist to analyze curvature and continuity behaviour of the shape. This paper deals with a new aspect of shape control: the stability of surfaces with respect to infnitesimal bendings. Each inEnitesimal bending of a surface determines a so called instability surface, which is used for the stability investigations. The kinematic meaning of this instability surface will be discussed and we present algorithms to calculate it.

- Visualization of Unstable Surface Regions (1995)
- Computer processing of free form surfaces forms the basis of a closed construction process starting with surface design and up to NC-production. Numerical simulation and visualization allow quality analysis before manufacture. A new aspect in surface analysis is described, the stability of surfaces versus infinitesimal bendings. The stability concept is derived from the kinetic meaning of a special vector field which is given by the deformation. Algorithms to calculate this vector field together with an appropriate visualization method give a tool able to analyze surface stability.

- Efficient algorithms for computing the \(L_2\) discrepancy (1995)
- The \(L_2\)-discrepancy is a quantitative measure of precision for multivariate quadrature rules. It can be computed explicitly. Previously known algorithms needed \(O(m^2\)) operations, where \(m\) is the number of nodes. In this paper we present algorithms which require \(O(m(log m)^d)\) operations.

- Variance reduction for Monte Carlo methods by means of deterministic numerical computation (1995)
- A new variance reduction technique for the Monte Carlo solution of integral equations is introduced. It is based on separation of the main part. A neighboring equation with exactly known solution is constructed by the help of a deterministic Galerkin scheme. The variance of the method is analyzed, and an application to the radiosity equation of computer graphics, together with numerical test results is given.