Analysing tactics in architectural patterns

We present an approach to analyse the application of tactics in architectural patterns. We define and illustrate the approach by resorting to Archery, a language for specifying, analysing and verifying architectural patterns. The approach consists of characterising the design principles of an architectural pattern as constraints, expressed in the language, and then, establishing a refinement relation based on their satisfaction. The application of tactics preserving refinement preserves the original design principles expressed themselves as constraints for the architectural pattern. The paper’s focus on fault-tolerance tactics, and identifies a set of requirements for a semantic framework characterising them. Model transformations to represent their application are discussed and illustrated through two case studies.FC

A synthesis of logic and biology in the design of dependable systems

The technologies of model-based design and dependability analysis in the design of dependable systems, including software intensive systems, have advanced in recent years. Much of this development can be attributed to the application of advances in formal logic and its application to fault forecasting and verification of systems. In parallel, work on bio-inspired technologies has shown potential for the evolutionary design of engineering systems via automated exploration of potentially large design spaces. We have not yet seen the emergence of a design paradigm that combines effectively and throughout the design lifecycle these two techniques which are schematically founded on the two pillars of formal logic and biology. Such a design paradigm would apply these techniques synergistically and systematically from the early stages of design to enable optimal refinement of new designs which can be driven effectively by dependability requirements. The paper sketches such a model-centric paradigm for the design of dependable systems that brings these technologies together to realise their combined potential benefits

A synthesis of logic and bio-inspired techniques in the design of dependable systems

Much of the development of model-based design and dependability analysis in the design of dependable systems, including software intensive systems, can be attributed to the application of advances in formal logic and its application to fault forecasting and verification of systems. In parallel, work on bio-inspired technologies has shown potential for the evolutionary design of engineering systems via automated exploration of potentially large design spaces. We have not yet seen the emergence of a design paradigm that effectively combines these two techniques, schematically founded on the two pillars of formal logic and biology, from the early stages of, and throughout, the design lifecycle. Such a design paradigm would apply these techniques synergistically and systematically to enable optimal refinement of new designs which can be driven effectively by dependability requirements. The paper sketches such a model-centric paradigm for the design of dependable systems, presented in the scope of the HiP-HOPS tool and technique, that brings these technologies together to realise their combined potential benefits. The paper begins by identifying current challenges in model-based safety assessment and then overviews the use of meta-heuristics at various stages of the design lifecycle covering topics that span from allocation of dependability requirements, through dependability analysis, to multi-objective optimisation of system architectures and maintenance schedules

A Catalog of Architectural Tactics for Cyber-Foraging

Mobile devices have become for many the preferred way of interacting with the Internet, social media and the enterprise. However, mobile devices still do not have the computing power or battery life that will allow them to perform effectively over long periods of time or for executing applications that require extensive communication or computation, or low latency. Cyber-foraging is a technique enabling mobile devices to extend their computing power and storage by offloading computation or data to more powerful servers located in the cloud or in single-hop proximity. This paper presents a catalog of architectural tactics for cyber-foraging that was derived from the results of a systematic literature review on architectures for cyber-foraging systems. Elements of the architectures identified in the primary studies were codified in the form of Architectural Tactics for Cyber-Foraging. These tactics will help architects extend their design reasoning towards cyber-foraging as a way to support the mobile applications of the present and the future

Representing Tactics for Fault Recovery: A Reconfigurable, Modular, and Hierarchical Approach

We show the advantages of modular and hierarchical design in obtaining fault-tolerant software. Modularity enables the identification of faulty software units simplifying key operations, like software removal and replacement. We describe three approaches to repair faulty software based on replication, namely, Passive Replication, N-Version Replication, and Active Replication, based on modular components. We show that the key construct to represent these tactics is the ability to make ad hoc changes in software topologies. We consider hierarchical mobility as a useful operation to introduce new software units for replacing faulty ones. For illustration purposes, we use connecton, a hierarchical, modular, and self-modifying software specification formalism, and its implementation in the Desmos framework

Implementing Reliability: The Interaction of Requirements, Tactics and Architecture Patterns

An important way that the reliability of a software system is enhanced is through the implementation of specific run-time measures called runtime tactics. Because reliability is a system-wide property, tactic implementations affect the software structure and behavior at the system, or architectural level. For a given architecture, different tactics may be a better or worse fit for the architecture, depending on the requirements and how the architecture patterns used must change to accommodate the tactic: different tactics may be a better or worse fit for the architecture. We found three important factors that influence the implementation of reliability tactics. One is the nature of the tactic, which indicates whether the tactic influences all components of the architecture or just a subset of them. The second is the interaction between architecture patterns and tactics: specific tactics and patterns are inherently compatible or incompatible. The third is the reliability requirements which influence which tactics to use and where they should be implemented. Together, these factors affect how, where, and the difficulty of implementing reliability tactics. This information can be used by architects and developers to help make decisions about which patterns and tactics to use, and can also assist these users in learning what modifications and additions to the patterns are needed.</p