An Event Algebra Extension of the Triggering Mechanism in a Component Model for Embedded Systems

AbstractIn this article we present how the component triggering in SaveCCM, a component model intended for embedded vehicular systems, can be extended by means of an event algebra. The extension allows components to be triggered by complex event patterns, and not only by clock signals or single external events.Separating the detection of triggering conditions from the definition of the triggered services permits more general components and thus improves component reusability. Providing event detection mechanisms within the component model means that triggering conditions are explicitly available for system analysis at design time.An event algebra is used to define the complex triggering conditions. This algebra has a relatively simple declarative semantics and well documented algebraic properties, which facilitates formal and informal reasoning about the system. The algebra also ensures that detection of triggering conditions can be efficiently implemented with limited resources, which is critical in embedded applications

Active database behaviour: the REFLEX approach

Modern day and new generation applications have more demanding requirements than traditional database management systems (DBMS) are able to support. Two of these requirements, timely responses to the change of database state and application domain knowledge stored within the database, are embodied within active database technology. Currently, there are a number of research prototype active database systems throughout the world. In order for an organisation to use any such prototype system, it may have to forsake existing products and resources and embark on substantial reinvestment in the new database products and associated resources and retraining costs. This approach would clearly be unfavourable as it is expensive both in terms of time and money. A more suitable approach would be to allow active behaviour to be added onto their existing systems. This scenario is addressed within this research. It investigates how best active behaviour can be augmented to existing DBMSs, so as to preserve the investments in an organisation's resources, by examining the following issues, (i.) what form the knowledge model should take, (ii.) should rules and events be modelled as first class objects, (iii.) how will the triggering events be specified, (iv.) how the user will interact with the system. Various design decisions were taken, which were investigated by implementation of a series of working prototypes, on the ONTOS DBMS platform. The resultant REFLEX model was successfully ported and adapted onto a second POET platform. The porting process uncovered some interesting issues regarding preconceived ideas about the portability of open systems

State-of-the-art on evolution and reactivity

This report starts by, in Chapter 1, outlining aspects of querying and updating resources on the Web and on the Semantic Web, including the development of query and update languages to be carried out within the Rewerse project. From this outline, it becomes clear that several existing research areas and topics are of interest for this work in Rewerse. In the remainder of this report we further present state of the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs; in Chapter 4 event-condition-action rules, both in the context of active database systems and in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks

A dataflow platform for applications based on Linked Data

Modern software applications increasingly benefit from accessing the multifarious and heterogeneous Web of Data, thanks to the use of web APIs and Linked Data principles. In previous work, the authors proposed a platform to develop applications consuming Linked Data in a declarative and modular way. This paper describes in detail the functional language the platform gives access to, which is based on SPARQL (the standard query language for Linked Data) and on the dataflow paradigm. The language features interactive and meta-programming capabilities so that complex modules/applications can be developed. By adopting a declarative style, it favours the development of modules that can be reused in various specific execution context

A Global Workspace perspective on mental disorders

Recent developments in Global Workspace theory suggest that human consciousness can suffer interpenetrating dysfunctions of mutual and reciprocal interaction with embedding environments which will have early onset and often insidiously staged developmental progression, possibly according to a cancer model. A simple rate distortion argument implies that, if an external information source is pathogenic, then sufficient exposure to it is sure to write a sufficiently accurate image of it on mind and body in a punctuated manner so as to initiate or promote simililarly progressively punctuated developmental disorder. There can, thus, be no simple, reductionist brain chemical 'bug in the program' whose 'fix' can fully correct the problem. On the contrary, the growth of an individual over the life course, and the inevitable contact with a toxic physical, social, or cultural environment, can be expected to initiate developmental problems which will become more intrusive over time, most obviously according to some damage accumulation model, but likely according to far more subtle, highly punctuated, schemes analogous to tumorigenesis. The key intervention, at the population level, is clearly to limit such exposures, a question of proper environmental sanitation, in a large sense, a matter of social justice which has long been understood to be determined almost entirely by the interactions of cultural trajectory, group power relations, and economic structure, with public policy. Intervention at the individual level appears limited to triggering or extending periods of remission, as is the case with most cancers

ALPACAS: A Language for Parametric Assessment of Critical Architecture Safety

This paper introduces Alpacas, a domain-specific language and algorithms aimed at architecture modeling and safety assessment for critical systems. It allows to study the effects of random and systematic faults on complex critical systems and their reliability. The underlying semantic framework of the language is Stochastic Guarded Transition Systems, for which Alpacas provides a feature-rich declarative modeling language and algorithms for symbolic analysis and Monte-Carlo simulation, allowing to compute safety indicators such as minimal cutsets and reliability. Built as a domain-specific language deeply embedded in Scala 3, Alpacas offers generic modeling capabilities and type-safety unparalleled in other existing safety assessment frameworks. This improved expressive power allows to address complex system modeling tasks, such as formalizing the architectural design space of a critical function, and exploring it to identify the most reliable variant. The features and algorithms of Alpacas are illustrated on a case study of a thrust allocation and power dispatch system for an electric vertical takeoff and landing aircraft

Event-triggered state observers for sparse sensor noise/attacks

This paper describes two algorithms for state reconstruction from sensor measurements that are corrupted with sparse, but otherwise arbitrary, 'noise.' These results are motivated by the need to secure cyber-physical systems against a malicious adversary that can arbitrarily corrupt sensor measurements. The first algorithm reconstructs the state from a batch of sensor measurements while the second algorithm is able to incorporate new measurements as they become available, in the spirit of a Luenberger observer. A distinguishing point of these algorithms is the use of event-triggered techniques to improve the computational performance of the proposed algorithms

Formal Object Interaction Language: Modeling and Verification of Sequential and Concurrent Object-Oriented Software

As software systems become larger and more complex, developers require the ability to model abstract concepts while ensuring consistency across the entire project. The internet has changed the nature of software by increasing the desire for software deployment across multiple distributed platforms. Finally, increased dependence on technology requires assurance that designed software will perform its intended function. This thesis introduces the Formal Object Interaction Language (FOIL). FOIL is a new object-oriented modeling language specifically designed to address the cumulative shortcomings of existing modeling techniques. FOIL graphically displays software structure, sequential and concurrent behavior, process, and interaction in a simple unified notation, and has an algebraic representation based on a derivative of the π-calculus. The thesis documents the technique in which FOIL software models can be mathematically verified to anticipate deadlocks, ensure consistency, and determine object state reachability. Scalability is offered through the concept of behavioral inheritance; and, FOIL’s inherent support for modeling concurrent behavior and all known workflow patterns is demonstrated. The concepts of process achievability, process complete achievability, and process determinism are introduced with an algorithm for simulating the execution of a FOIL object model using a FOIL process model. Finally, a technique for using a FOIL process model as a constraint on FOIL object system execution is offered as a method to ensure that object-oriented systems modeled in FOIL will complete their processes based activities. FOIL’s capabilities are compared and contrasted with an extensive array of current software modeling techniques. FOIL is ideally suited for data-aware, behavior based systems such as interactive or process management software