A Language for Configuring Multi-level Specifications

This paper shows how systems can be built from their component parts with specified sharing. Its principle contribution is a modular language for configuring systems. A configuration is a description in the new language of how a system is constructed hierarchically from specifications of its component parts. Category theory has been used to represent the composition of specifications that share a component part by constructing colimits of diagrams. We reformulated this application of category theory to view both configured specifications and their diagrams as algebraic presentations of presheaves. The framework of presheaves leads naturally to a configuration language that expresses structuring from instances of specifications, and also incorporates a new notion of instance reduction to extract the component instances from a particular configuration. The language now expresses the hierarchical structuring of multi-level configured specifications. The syntax is simple because it is independent of any specification language; structuring a diagram to represent a configuration is simple because there is no need to calculate a colimit; and combining specifications is simple because structuring is by configuration morphisms with no need to flatten either specifications or their diagrams to calculate colimits

Uniform Interfaces for Resource-Sharing Components in Hierarchically Scheduled Real-Time Systems

In literature, several hierarchical scheduling frameworks (HSFs) have been proposed for enabling resource sharing between components on a uni-processor system. Each HSF comes with its own set of composition rules which take into account a specific synchronization protocol for arbitrating access to resources. However, the inventors of these synchronization protocols have also chosen to describe these composition rules with the help of protocol-specific component interfaces. This creates unnecessary framework dependencies on components

A Service Component-based Accounting and Charging Architecture to Support Interim Mechanisms across Multiple Domains

Today, telematics services are often compositions of different chargeable service components offered by different service providers. To enhance component-based accounting and charging, the service composition information is used to match with the corresponding charging structure of a service session. This enables the sharing of revenues among the service providers, and calculation of the total cost for the end-user. When multiple independent service providers are involved, it is a great challenge to apply interim accounting and charging during a service session in order to minimize financial risks between business partners. Another interesting development is the trend towards outsourcing accounting and charging processes to specialized business partners. This requires a decoupling between provisioning and accounting and charging processes. In this paper, we propose a comprehensive component-based accounting and charging architecture to support service session provisioning across multiple domains. The architecture, modeled in UML, incorporates an interim accounting and charging mechanism to enable the processing and exchange of accounting information needed to update intermediate charges for separate service components and the user's credit, even during the service provisioning phase

The reflective component of the Mellow Bumps parenting intervention: Implementation, engagement and mechanisms of change

Understanding why parenting programmes work or do not work, and for whom, is crucial for development of more effective parenting interventions. In this paper we focus on a specific component of Mellow Bumps: reflection on one’s own childhood/past/life. We explore how this component was implemented, how participants engaged with it, the facilitating and constraining factors shaping this, whether and how it appeared to work, or not, and for whom. The paper analyses data from the Process Evaluation of the Trial of Healthy Relationships Initiatives for the Very Early years, which is evaluating two antenatal interventions delivered to vulnerable women, one of which is Mellow Bumps. Data were collected from January 2014 to June 2018 for 28 groups, 108 participants and 24 facilitators in a comprehensive and rigorous Process Evaluation designed to complement the Outcome Evaluation. Data were gathered at various time points using multiple methods, and were synthesised to triangulate findings. The reflective component was implemented with fidelity and participants engaged with it to varying degrees, dependent largely on the coherence of the group. Patchy attendance compromised the coherence of some groups, with the development of rapport, which is key to delivering reflective exercises, more difficult when group composition varied from week to week. Where there was a coherent group, powerful mechanisms of change, leading to stress reduction, included: relief through unburdening, empowerment through support given and received, reduced isolation through sharing anxieties, and control through self-care advice. A minority of highly vulnerable mothers seemed not to benefit from the reflective exercises and were marginalised within their groups. In order to minimise potential harmful effects of such exercises, allocation of participants to groups should strive to maximise group homogeneity. More research is needed to explore how very vulnerable parents can be supported in attending parenting interventions from start to finish

Physics Potential of a Radio Surface Array at the South Pole (ARENA 2018)

A surface array of radio antennas will enhance the performance of the IceTop array and enable new, complementary science goals. First, the accuracy for cosmic-ray air showers will be increased since the radio array provides a calorimetric measurement of the electromagnetic component and is sensitive to the position of the shower maximum. This enhanced accuracy can be used to better measure the mass composition, to search for possible mass-dependent anisotropies in the arrival directions of cosmic rays, and for more thorough tests of hadronic interaction models. Second, the sensitivity of the radio array to inclined showers will increase the sky coverage for cosmic-ray measurements. Third, the radio array can be used to search for PeV photons from the Galactic Center. Since IceTop is planned to be enhanced by a scintillator array in the near future, a radio extension sharing the same infrastructure can be installed with minimal additional effort and excellent scientific prospects. The combination of ice-Cherenkov, scintillation, and radio detectors at IceCube will provide unprecedented accuracy for the study of highenergy Galactic cosmic rays.Comment: Proceedings of 8th ARENA 2018, to appear in EPJ Wo

BiLog - A Framework for Structural Logics (talk)

Talk given at Forum on Separation Logics, Cambridge 14.03.0

Exports and Wages: Rent Sharing, Workforce Composition or Returns to Skills?

We use linked employer-employee data from Italy to explore the relationship between exports and wages. Our empirical strategy exploits the 1992 devaluation of the Italian Lira, which represented a large and unforeseen shock to Italian firms’ incentives to export. The results indicate that the export wage premium is due to exporting firms both (a) paying a wage premium above what their workers would earn in the outside labor market – the “rent-sharing” effect, and (b) employing workers whose skills command a higher price after the devaluation – the “skill composition” effect. The latter effect only emerges once we allow for the value of individual skills to differ in the pre and post-devaluation periods. In fact, using a fixed measure of skills, as typically done in the literature, we would attribute the wage increase only to rent sharing. We also document that the export wage premium is larger for workers with more export-related experience. This indicates that the devaluation increased the demand for skills more useful for exporting, driving their relative price up

Shared Event Composition/Decomposition in Event-B

The construction of specifications is often a combination of smaller sub-components. Composition and decomposition are techniques that support reuse and allow us to formally combine sub-components through refinement steps while reusing their properties. Sub-components can result from a design or architectural goal and a refinement framework should allow further parallel development over the sub-components. We propose the definition of composition and decomposition in the Event-B formalism following a shared event approach where sub-components interact via synchronisation over shared events and shared states are not allow. We define the necessary proof obligations to ensure a valid composition or decomposition. We also show that shared event composition preserves refinement proofs for sub-components, that is, in order to maintain refinement of compositions, it is sufficient to prove refinement between corresponding subcomponents. A case study applying these two techniques is illustrated using Rodin, the Event-B toolset

A conceptual architecture for semantic web services development and deployment

Several extensions of the Web Services Framework (WSF) have been proposed. The combination with Semantic Web technologies introduces a notion of semantics, which can enhance scalability through automation. Service composition to processes is an equally important issue. Ontology technology – the core of the Semantic Web – can be the central building block of an extension endeavour. We present a conceptual architecture for ontology-based Web service development and deployment. The development of service-based software systems within the WSF is gaining increasing importance. We show how ontologies can integrate models, languages, infrastructure, and activities within this architecture to support reuse and composition of semantic Web services