Interner Bericht des Fachbereich Informatik
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264
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.
366
Guaranteeing correctness of compilation is a ma jor precondition for correct software. Code generation can be one of the most error-prone tasks in a compiler. One way to achieve trusted compilation is certifying compilation. A certifying compiler generates for each run a proof that it has performed the compilation run correctly. The proof is checked in a separate theorem prover. If the theorem prover is content with the proof, one can be sure that the compiler produced correct code. This paper presents a certifying code generation phase for a compiler translating an intermediate language into assembler code. The time spent for checking the proofs is the bottleneck of certifying compilation. We exhibit an improved framework for certifying compilation and considerable advances to overcome this bottleneck. We compare our implementation featuring the Coq theorem prover to an older implementation. Our current implementation is feasible for medium to large sized programs.
361
Abstraction is intensively used in the verification of large, complex or infinite-state systems. With abstractions getting more complex it is often difficult to see whether they are valid. However, for using abstraction in model checking it has to be ensured that properties are preserved. In this paper, we use a translation validation approach to verify property preservation of system abstractions. We formulate a correctness criterion based on simulation between concrete and abstract system for a property to be verified. For each distinct run of the abstraction procedure the correctness is verified in the theorem prover Isabelle/HOL. This technique is applied in the verification of embedded adaptive systems. This paper is an extended version a previously published work.
332
Many applications dealing with geometry acquisition and processing produce polygonal meshes that carry artifacts like discretization noise. While there are many approaches to remove the artifacts by smoothing or filtering the mesh, they are not tailored to any specific application subject to·certain restrictive objectives. We show how to incorporate smoothing schemes based on the general Laplacian approximation to satsify all those objectives at
the same time for the results of flow simulation in the application field of car manufacturing. In the presented application setting the major restrictions come from the bounding volume of the flow simulation, the so-called installation space. In particular, clean mesh regions (without noise) should not be smoothed while at the same time the installation space must not be violated by the smoothing of the noisy mesh regions. Additionally, aliasing effects at the boundary between clean and noisy mesh regions must be prevented. To address the fact that the meshes come from flow simulation, the presented method is versatile enough to preserve their exact volume and to apply anisotropic filters using the flow information.
Although the paper focuses on the results of a specific application, most of its findings can be transferred to different settings as well.
305
The quality of freeform surfaces is one of the major topics of CAD/CAM. Aesthetic and technical demands require the construction of high quality surfaces with strong shape conditions. Quality diminishing properties like dents or flat points have to be eliminated while approximation conditions must hold at the same time. Our approach combines quality and approximation criteria to a nonlinear multicriteria optimization problem and achieves an automatic approximation and fitting process.
382
This report gives an overview of the separate translation of synchronous imperative programs to synchronous guarded actions. In particular, we consider problems to be solved for separate compilation that stem from preemption statements and local variable declarations. We explain how we solved these problems and sketch our solutions implemented in the our Averest framework to implement a compiler that allows a separate compilation of imperative synchronous programs with local variables and unrestricted preemption statements. The focus of the report is the big picture of our entire design flow.
387
SHIM is a concurrent deterministic programming language for embedded systems built on rendezvous communication. It abstracts away many details to give the developer a high-level view that includes virtual shared variables, threads as orthogonal statements, and deterministic concurrent exceptions.
In this paper, we present a new way to compile a SHIM-like language into a set of asynchronous guarded actions, a well-established intermediate representation for concurrent systems. By doing so, we build a bridge to many other tools, including hardware synthesis and formal verification. We present our translation in detail, illustrate it through examples, and show how the result can be used by various other tools.
273
The feature interaction problem in telecommunications systems increasingly ob-structs the evolution of such systems. We develop formal detection criteria whichrender a necessary (but less than sufficient) condition for feature interactions. It can be checked mechanically and points out all potentially critical spots. Thesehave to be analysed manually. The resulting resolution decisions are incorporatedformally. Some prototype tool support is already available. A prerequisite forformal criteria is a formal definition of the problem. Since the notions of featureand feature interaction are often used in a rather fuzzy way, we attempt a formaldefinition first and discuss which aspects can be included in a formalization (andtherefore in a detection method). This paper describes ongoing work.
245
A Case Study on Specifikation,Detection and Resolution of IN Feature Interactions with Estelle
(1994)
We present an approach for the treatment of Feature Interactions in Intelligent Networks. The approach is based on the formal description technique Estelle and consists of three steps. For the first step, a specification style supporting the integration of additional features into a basic service is introduced . As a result, feature integration is achieved by adding specification text, i.e . on a purely syntactical level. The second step is the detection of feature interactions resulting from the integration of additional features. A formal criterion is given that can be used for the automatic detection of a particular class of feature interactions. In the third step, previously detected feature interactions are resolved. An algorithm has been devised that allows the automatical incorporation of high-level design decisions into the formal specification. The presented approach is applied to the Basic Call Service and several supplementary interacting features.
244
We introduce the concept of streamballs for fluid flow visualization. Streamballs are based upon implicit surface generation techniques adopted from the well-known metaballs. Their property to split or merge automatically in areas of significant divergence or convergence makes them an ideal tool for the visualization of arbitrary complex flow fields. Using convolution surfaces generated by continuous skeletons for streamball construction offers the possibility to visualize even tensor fields.