Easing the Transition from Inspiration to Implementation: A Rapid Prototyping Platform for Wireless Medium Access Control Protocols

Packet broadcast networks are in widespread use in modern wireless communication systems. Medium access control is a key functionality within such technologies. A substantial research effort has been and continues to be invested into the study of existing protocols and the development of new and specialised ones. Academic researchers are restricted in their studies by an absence of suitable wireless MAC protocol development methods. This thesis describes an environment which allows rapid prototyping and evaluation of wireless medium access control protocols. The proposed design flow allows specification of the protocol using the specification and description language (SDL) formal description technique. A tool is presented to convert the SDL protocol description into a C++ model suitable for integration into both simulation and implementation environments. Simulations at various levels of abstraction are shown to be relevant at different stages of protocol design. Environments based on the Cinderella SDL simulator and the ns-2 network simulator have been developed which allow early functional verification, along with detailed and accurate performance analysis of protocols under development. A hardware platform is presented which allows implementation of protocols with flexibility in the hardware/software trade-off. Measurement facilities are integral to the hardware framework, and provide a means for accurate real-world feedback on protocol performance

Executable Model Synthesis and Property Validation for Message Sequence Chart Specifications

Message sequence charts (MSC’s) are a formal language for the specification of scenarios in concurrent real-time systems. The thesis addresses the synthesis of executable object-oriented design-time models from MSC specifications. The synthesis integrates with the software development process, its purpose being to automatically create working prototypes from specifications without error and create executable models on which properties may be validated. The usefulness of existing algorithms for the synthesis of ROOM (Real-Time Object Oriented Modeling) models from MSC’s has been evaluated from the perspective of an applications programmer ac-cording to various criteria. A number of new synthesis features have been proposed to address them, and applied to a telephony call management system for illustration. These include the specification and construction of hierarchical structure and behavior of ROOM actors, views, multiple containment, replication, resolution of non-determinism and automatic coordination. Generalizations and algorithms have been provided. The hierarchical actor structure, replication, FSM merging, and global coordinator algorithms have been implemented in the Mesa CASE tool. A comparison is made to other specification and modeling languages and their synthesis, such as SDL, LSC’s, and statecharts. Another application of synthesis is to generate a model with support for the automated validation of safety and liveness properties. The Mobility Management services of the GSM digital mobile telecommunications system were specified in MSC’s. A Promela model of the system was then synthesized. A number of optimizations have been proposed to reduce the complexity of the model in order to successfully perform a validation of it. Properties of the system were encoded in Linear Temporal Logic, and the Promela model was used to automatically validate a number of identified properties using the model checker Spin. A ROOM model was then synthesized from the validated MSC specification using the proposed refinement features

Requirements of an Integrated Formal Method for Intelligent Swarms

NASA is investigating new paradigms for future space exploration, heavily focused on the (still) emerging technologies of autonomous and autonomic systems [47, 48, 49]. Missions that rely on multiple, smaller, collaborating spacecraft, analogous to swarms in nature, are being investigated to supplement and complement traditional missions that rely on one large spacecraft [16]. The small spacecraft in such missions would each be able to operate on their own to accomplish a part of a mission, but would need to interact and exchange information with the other spacecraft to successfully execute the mission

Verificare: a platform for composable verification with application to SDN-Enabled systems

Software-Defined Networking (SDN) has become increasing prevalent in both the academic and industrial communities. A new class of system built on SDNs, which we refer to as SDN-Enabled, provide programmatic interfaces between the SDN controller and the larger distributed system. Existing tools for SDN verification and analysis are insufficiently expressive to capture this composition of a network and a larger distributed system. Generic verification systems are an infeasible solution, due to their monolithic approach to modeling and rapid state-space explosion. In this thesis we present a new compositional approach to system modeling and verification that is particularly appropriate for SDN-Enabled systems. Compositional models may have sub-components (such as switches and end-hosts) modified, added, or removed with only minimal, isolated changes. Furthermore, invariants may be defined over the composed system that restrict its behavior, allowing assumptions to be added or removed and for components to be abstracted away into the service guarantee that they provide (such as guaranteed packet arrival). Finally, compositional modeling can minimize the size of the state space to be verified by taking advantage of known model structure. We also present the Verificare platform, a tool chain for building compositional models in our modeling language and automatically compiling them to multiple off-the-shelf verification tools. The compiler outputs a minimal, calculus-oblivious formalism, which is accessed by plugins via a translation API. This enables a wide variety of requirements to be verified. As new tools become available, the translator can easily be extended with plugins to support them

Integrating the theme approach with aspectual scenarios

Dissertação de Mestrado em Engenharia InformáticaAspect-oriented requirements engineering emerged to deal with crosscutting requirements, i.e. requirements that are scattered in the requirements document and tangled with other requirements. There are several aspect-oriented requirements approaches - Theme, proposed by Baniassad and Clarke [7], is one of them. This approach is characterized by the identification of a set of actions associated to verbs present in requirements documentation. These actions are then analyzed in order to identify crosscutting behaviours, each one constituting a potential theme. One problem with this approach is that the composition mechanism is not expressive enough even when the Theme models are integrated to analysis models (e.g. UML diagrams). The MATA approach [24] provides powerful composition mechanisms, based on graph transformations that used UML models, in particular behaviour models (e.g. sequence or activity like diagrams). These models express scenarios that constitute a very popular and used technique to specify a system’s behaviour. Therefore, the result of the integration of these two approaches will be synergetic. Also, considering that in a system not only the expected situations happen, scenarios can also be used to illustrate unexpected situations, making their treatment possible. Negative scenarios are thus also considered, besides the positive ones: their representation is similar, only differing from an optimist and mostly assumed vision of the system’s behavior. These scenarios could be identified with Theme and mapped into MATA. In summary, the objective of this dissertation is twofold: firstly, we will integrate Theme with Aspectual Scenarios (specified in MATA); secondly, we will extend Theme to include the modeling of negative scenarios. The result will be the synergy between two complementary techniques, including the specification of undesirable situations, where behavioral and structural aspect modeling are integrated

A Design Rationale for Pervasive Computing - User Experience, Contextual Change, and Technical Requirements

The vision of pervasive computing promises a shift from information technology per se to what can be accomplished by using it, thereby fundamentally changing the relationship between people and information technology. In order to realize this vision, a large number of issues concerning user experience, contextual change, and technical requirements should be addressed. We provide a design rationale for pervasive computing that encompasses these issues, in which we argue that a prominent aspect of user experience is to provide user control, primarily founded in human values. As one of the more significant aspects of the user experience, we provide an extended discussion about privacy. With contextual change, we address the fundamental change in previously established relationships between the practices of individuals, social institutions, and physical environments that pervasive computing entails. Finally, issues of technical requirements refer to technology neutrality and openness--factors that we argue are fundamental for realizing pervasive computing. We describe a number of empirical and technical studies, the results of which have helped to verify aspects of the design rationale as well as shaping new aspects of it. The empirical studies include an ethnographic-inspired study focusing on information technology support for everyday activities, a study based on structured interviews concerning relationships between contexts of use and everyday planning activities, and a focus group study of laypeople’s interpretations of the concept of privacy in relation to information technology. The first technical study concerns the model of personal service environments as a means for addressing a number of challenges concerning user experience, contextual change, and technical requirements. Two other technical studies relate to a model for device-independent service development and the wearable server as a means to address issues of continuous usage experience and technology neutrality respectively