Equivalence Checking of Sequential Quantum Circuits

We define a formal framework for equivalence checking of sequential quantum circuits. The model we adopted is a quantum state machine, which is a natural quantum generalisation of Mealy machines. A major difficulty in checking quantum circuits (but not present in checking classical circuits) is that the state spaces of quantum circuits are continuums. This difficulty is resolved by our main theorem showing that equivalence checking of two quantum Mealy machines can be done with input sequences that are taken from some chosen basis (which are finite) and have a length quadratic in the dimensions of the state Hilbert spaces of the machines. Based on this theoretical result, we develop an (and to the best of our knowledge, the first) algorithm for checking equivalence of sequential quantum circuits. A case study and experiments are presented

A Model-based Approach for Designing Cyber-Physical Production Systems

The most recent development trend related to manufacturing is called "Industry 4.0". It proposes to transition from "blind" mechatronics systems to Cyber-Physical Production Systems (CPPSs). Such systems are capable of communicating with each other, acquiring and transmitting real-time production data. Their management and control require a structured software architecture, which is tipically referred to as the "Automation Pyramid". The design of both the software architecture and the components (i.e., the CPPSs) is a complex task, where the complexity is induced by the heterogeneity of the required functionalities. In such a context, the target of this thesis is to propose a model-based framework for the analysis and the design of production lines, compliant with the Industry 4.0 paradigm. In particular, this framework exploits the Systems Modeling Language (SysML) as a unified representation for the different viewpoints of a manufacturing system. At the components level, the structural and behavioral diagrams provided by SysML are used to produce a set of logical propositions about the system and components under design. Such an approach is specifically tailored towards constructing Assume-Guarantee contracts. By exploiting reactive synthesis techniques, contracts are used to prototype portions of components' behaviors and to verify whether implementations are consistent with the requirements. At the software level, the framework proposes a particular architecture based on the concept of "service". Such an architecture facilitates the reconfiguration of components and integrates an advanced scheduling technique, taking advantage of the production recipe SysML model. The proposed framework has been built coupled with the construction of the ICE Laboratory, a research facility consisting of a full-fledged production line. Such an approach has been adopted to construct models of the laboratory, to virtual prototype parts of the system and to manage the physical system through the proposed software architecture

Symmetric and efficient synthesis

Since the formulation of the synthesis problem for reactive systems by Church in the 60s, research on synthesis has lead to both theoretical insights and practical approaches for automatically constructing systems from their specifications. While the first solution of the problem was given by Büchi as early as 1969, only very recently, focus has shifted towards identifying ways to exploit the structure in reactive system specifications in order to lift the scalability of synthesis to industrial-sized designs. The recent progress in synthesis not only lead to a renewed interest in the subject, but also shed light onto the downsides of current synthesis approaches. In the original formulation of the problem, the structure of the produced solutions was not a concern. Experiments with current synthesis approaches has however shown that the computed implementations are usually very hard to understand and have little of the structure that manually constructed implementations have. Furthermore, the scalability of current synthesis approaches is still deemed to be insufficient for many industrial application scenarios, which prevents the introduction of reactive synthesis technology into industrial design flows. In this thesis, we tackle both of these problems for reactive synthesis. To counter the insufficient structure in the solutions, we analyse the problem of symmetric synthesis. In this alternative synthesis problem, the aim is to compute a solution that consists of multiple copies of the same process such that the overall system satisfies the specification. Such systems have no centralised control units, and are considered to be more robust and easier to maintain. We characterise undecidable and decidable cases of the problem, and provide a synthesis algorithm for rotation-symmetric architectures, which capture many cases of practical relevance. To improve the scalability in synthesis, we start with a simple but scalable approach to reactive synthesis that has shown its principal applicability in the field, and extend its main idea both in terms of scope and usability. We enhance its expressivity in a way that allows to synthesise robust systems, and remove its limitation to specifications of a very special form. Both improvements yield theoretical insights into the synthesis problem: we characterise which specification classes can be supported in synthesis approaches that use parity games with a fixed number of colours as the underlying computation model, and examine the properties of universal very-weak automata, on which we base a synthesis workflow that combines ease of specification with a low complexity of the underlying game solving step. As a side-result, we also obtain the first procedure to translate a formula in linear-time temporal logic (LTL) to a computation tree logic (CTL) formula with only universal path quantifiers, whenever possible. The new results on symmetric and efficient reactive synthesis are complemented by an easily accessible introductory chapter to the field of reactive synthesis that can also be read in isolation.paddle apparatus with membrane holder were identified.Trotz der Vorzüge der Synthese reaktiver Systeme gegenüber der manuellen Konstruktion solcher Systeme ist Synthese noch nicht als Teil industrieller Vorgehensmodelle etabliert. Als Hauptgrund für diese Diskrepanz gilt allgemein, dass sowohl die Qualität der synthetisierten Systeme bei Anwendung bisheriger Methoden unzureichend ist, als auch die Skalierbarkeit aktueller Syntheseverfahren der Verbesserung bedarf. Diese Dissertation behandelt beide diese Probleme der Synthese reaktiver Systeme auf breiter Front. Zur Verbesserung der Qualität synthetisierter Systeme wird die Synthese von strukturierten Systemen betrachtet. Experimente mit aktuellen Syntheseverfahren haben gezeigt, dass die erzeugten Implementierungen oft schwer zu verstehen sind und anders als handgeschriebene Implementierungen kaum Struktur haben. Abhilfe verschafft die Beschränkung auf die Erzeugung symmetrischer Systeme, die aus mehreren Kopien des selben Prozesses bestehen, so dass das Gesamtsystem die Spezifikation erfüllt. Solche Systeme haben keine zentrale Koordinationskomponente und werden allgemein als robuster und einfacher zu warten eingestuft. In dieser Dissertation werden entscheidbare und unentscheidbare Fälle des symmetrischen Syntheseproblems identifiziert und ein Synthesealgorithmus für rotationssymmetrische Systeme beschrieben. Diese Systemklasse deckt viele praktisch relevante Architekturen ab. Um das Problem der mangelnden Skalierbarkeit anzugehen, wird die Hauptidee des Generalised Reactivity(1) Syntheseansatzes, welcher seine praktische Anwendbarkeit bereits unter Beweis gestellt hat, aufgegriffen und sowohl bezüglich der Expressivität als auch der Benutzbarkeit vervollständigt. Die Erweiterung der Expressivität ermöglicht es, den resultierenden Ansatz für die Synthese robuster Systeme zu nutzen, während die Benutzbarkeit für industrielle Anwendungen durch die Aufhebung der Beschränkung, dass die Spezifikation eine sehr spezielle Form haben muss, erreicht wird. Beide Erweiterungen geben Einsicht in die Theorie der Synthese: Zum einen wird die Klasse der Spezifikationen, die in Syntheseansätzen verwendet werden können, die auf dem Lösen von Paritätsspielen mit einer vordefinierten Anzahl von Farben basieren, charakterisiert. Zum anderen wird Einsicht in die Eigenschaften universeller sehr schwacher Automaten gegeben. Ein Nebenprodukt der neuen Syntheseverfahren ist die erste Prozedur, um einen Ausdruck in linear-time temporal logic (LTL) in computation tree logic mit universellen Pfadquantoren (ACTL) zu übersetzen, wann immer dies möglich ist. Die Resultate zur symmetrischen und effizienten reaktiven Synthese werden von einer didaktisch aufbereiteten Einführung in das Gebiet der reaktiven Synthese begleitet, welche auch unabhängig von den übrigen Teilen der Dissertation gelesen werden kann

Measurements, Models, Systems and Design

531 s.

An evolutionary approach to the use of Petri net based models: from parallel controllers to HW/SW co-design

"A workshop within the 19th International Conference on Applications and Theory of Petri Nets - ICATPN’1998"The main purpose of this article is to present how Petri Nets (PNs) have been used for hardware design at our research laboratory. We describe the use of PN models to specify synchronous parallel controllers and how PN speci cations can be extended to include the behavioural description of the data path, by using object-oriented concepts. Some hierarchical mechanisms which deal with the speci cation of complex digital systems are highlighted. It is described a design flow that includes, among others, the automatic generation of VHDL code to synthesize the control unit of the system. The use of PNs as part of a multiple-view model within an object-oriented methodology for hardware/software codesign is debated. The EDgAR-2 platform is considered as the recon gurable target architecture for implementing the systems and its main characteristics are shown

Applying Formal Methods to Networking: Theory, Techniques and Applications

Despite its great importance, modern network infrastructure is remarkable for the lack of rigor in its engineering. The Internet which began as a research experiment was never designed to handle the users and applications it hosts today. The lack of formalization of the Internet architecture meant limited abstractions and modularity, especially for the control and management planes, thus requiring for every new need a new protocol built from scratch. This led to an unwieldy ossified Internet architecture resistant to any attempts at formal verification, and an Internet culture where expediency and pragmatism are favored over formal correctness. Fortunately, recent work in the space of clean slate Internet design---especially, the software defined networking (SDN) paradigm---offers the Internet community another chance to develop the right kind of architecture and abstractions. This has also led to a great resurgence in interest of applying formal methods to specification, verification, and synthesis of networking protocols and applications. In this paper, we present a self-contained tutorial of the formidable amount of work that has been done in formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial