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.
The Super-Peer Selection Problem is an optimization problem in network topology construction. It may be cast as a special case of a Hub Location Problem, more exactly an Uncapacitated Single Allocation p-Hub Median Problem with equal weights. We show that this problem is still NP-hard by reduction from Max Clique.
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.
The provision of network Quality-of-Service (network QoS) in wireless (ad-hoc) networks is a major challenge in the development of future communication systems. Before designing and implementing these systems, the network QoS requirements are to be specified. Since QoS functionalities are integrated across layers and hence QoS specifications exist on different system layers, a QoS mapping technique is needed to translate the specifications into each other. In this paper, we formalize the relationship between layers. Based on a comprehensive and holistic formalization of network QoS requirements, we define two kinds of QoS mappings. QoS domain mappings associate QoS domains of two abstraction levels. QoS scalability mappings associate utility and cost functions of two abstraction levels. We illustrate our approach by examples from the case study Wireless Video Transmission.
The provision of network Quality-of-Service (network QoS) in wireless (ad-hoc) networks is a major challenge in the development of future communication systems. Before designing and implementing these systems, the network QoS requirements are to be specified. Existing approaches to the specification of network QoS requirements are mainly focused on specific domains or individual system layers. In this paper, we present a holistic, comprehensive formalization of network QoS requirements, across layers. QoS requirements are specified on each layer by defining QoS domain, consisting of QoS performance, reliability, and guarantee, and QoS scalability, with utility and cost functions. Furthermore, we derive preorders on multi-dimensional QoS domains, and present criteria to reduce these domains, leading to a manageable subset of QoS values that is sufficient for system design and implementation. We illustrate our approach by examples from the case study Wireless Video Transmission.