@phdthesis{Appold2015,
  author    = {Appold, Christian},
  title     = {Symbolische BDD-basierte Modellpr{\"u}fung asynchroner nebenl{\"a}ufiger Systeme},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-137029},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {Today, information and communication systems are ubiquitous and consist very often of several interacting and communicating components. One reason is the widespread use of multi-core processors and the increasing amount of concurrent software for the efficient usage of multi-core processors. Also, the dissemination of distributed emergent technologies like sensor networks or the internet of things is growing. Additionally, a lot of internet protocols are client-server architectures with clients which execute computations in parallel and servers that can handle requests of several clients in parallel. Systems which consist of several interacting and communicating components are often very complex and due to their complexity also prone to errors. Errors in systems can have dramatic consequenses, especially in safety-critical areas where human life can be endangered by incorrect system behavior. Hence, it is inevitable to have methods that ensure the proper functioning of such systems. This thesis aims on improving the verifiability of asynchronous concurrent systems using symbolic model checking based on Binary Decision Diagrams (BDDs). An asynchronous concurrent system is a system that consists of several components, from which only one component can execute a transition at a time. Model checking is a formal verification technique. For a given system description and a set of desired properties, the validity of the properties for the system is decided in model checking automatically by software tools called model checkers. The main problem of model checking is the state-space explosion problem. One approach to reduce this problem is the use of symbolic model checking. There, system states and transitions are not stored explicitely as in explicit model checking. Instead, in symbolic model checking sets of states and sets of transitions are stored and also manipulated together. The data structure which is used in this thesis to store those sets are BDDs. BDD-based symbolic model checking has already been used successful in industry for several times. Nevertheless, BDD-based symbolic model checking still suffers from the state-space explosion problem and further improvements are necessary to improve its applicability. Central operations in BDD-based symbolic model checking are the computation of successor and predecessor states of a given set of states. Those computations are called image computations. They are applied repeatedly in BDD-based symbolic model checking to decide the validity of properties for a given system description. Hence, their efficient execution is crucial for the memory and runtime requirements of a model checker. In an image computation a BDD for a set of transitions and a BDD for a set of states are combined to compute a set of successor or predecessor states. Often, also the size of the BDDs to represent the transition relation is critical for the successful use of model checking. To further improve the applicability of symbolic model checking, we present in this thesis new data structures to store the transition relation of asynchronous concurrent systems. Additionally, we present new image computation algorithms. Both can lead to large runtime and memory reductions for BDD-based symbolic model checking. Asynchronous concurrent systems often contain symmetries. A technique to exploit those symmetries to diminish the state-space explosion problem is symmetry reduction. In this thesis we also present a new efficient algorithm for symmetry reduction in BDD-based symbolic model checking.},
  subject      = {Programmverifikation},
  language  = {de}
}