Synthesizing Finite-state Protocols from Scenarios and Requirements

Scenarios, or Message Sequence Charts, offer an intuitive way of describing the desired behaviors of a distributed protocol. In this paper we propose a new way of specifying finite-state protocols using scenarios: we show that it is possible to automatically derive a distributed implementation from a set of scenarios augmented with a set of safety and liveness requirements, provided the given scenarios adequately \emph{cover} all the states of the desired implementation. We first derive incomplete state machines from the given scenarios, and then synthesis corresponds to completing the transition relation of individual processes so that the global product meets the specified requirements. This completion problem, in general, has the same complexity, PSPACE, as the verification problem, but unlike the verification problem, is NP-complete for a constant number of processes. We present two algorithms for solving the completion problem, one based on a heuristic search in the space of possible completions and one based on OBDD-based symbolic fixpoint computation. We evaluate the proposed methodology for protocol specification and the effectiveness of the synthesis algorithms using the classical alternating-bit protocol.Comment: This is the working draft of a paper currently in submission. (February 10, 2014

Synthesis of Switching Protocols from Temporal Logic Specifications

We propose formal means for synthesizing switching protocols that determine the sequence in which the modes of a switched system are activated to satisfy certain high-level specifications in linear temporal logic. The synthesized protocols are robust against exogenous disturbances on the continuous dynamics. Two types of finite transition systems, namely under- and over-approximations, that abstract the behavior of the underlying continuous dynamics are defined. In particular, we show that the discrete synthesis problem for an under-approximation can be formulated as a model checking problem, whereas that for an over-approximation can be transformed into a two-player game. Both of these formulations are amenable to efficient, off-the-shelf software tools. By construction, existence of a discrete switching strategy for the discrete synthesis problem guarantees the existence of a continuous switching protocol for the continuous synthesis problem, which can be implemented at the continuous level to ensure the correctness of the nonlinear switched system. Moreover, the proposed framework can be straightforwardly extended to accommodate specifications that require reacting to possibly adversarial external events. Finally, these results are illustrated using three examples from different application domains

Quantum and classical resources for unitary design of open-system evolutions

A variety of tasks in quantum control, ranging from purification and cooling to quantum stabilisation and open-system simulation, rely on the ability to implement a target quantum channel over a specified time interval within prescribed accuracy. This can be achieved by engineering a suitable unitary dynamics of the system of interest along with its environment, which, depending on the available level of control, is fully or partly exploited as a coherent quantum controller. After formalising a controllability framework for completely positive trace-preserving quantum dynamics, we provide sufficient conditions on the environment state and dimension that allow for the realisation of relevant classes of quantum channels, including extreme channels, stochastic unitaries or simply any channel. The results hinge on generalisations of Stinespring's dilation via a subsystem principle. In the process, we show that a conjecture by Lloyd on the minimal dimension of the environment required for arbitrary open-system simulation, albeit formally disproved, can in fact be salvaged, provided that classical randomisation is included among the available resources. Existing measurement-based feedback protocols for universal simulation, dynamical decoupling and dissipative state preparation are recast within the proposed coherent framework as concrete applications, and the resources they employ discussed in the light of the general results

Building Information Modelling [BIM] for energy efficiency in housing refurbishments

Building Information modelling offers potential process and delivery improvements throughout the lifecycle of built assets. However, there is limited research in the use of BIM for energy efficiency in housing refurbishments. The UK has over 300,000 solid wall homes with very poor energy efficiency. A BIM based solution for the retrofit of solid wall housing using lean and collaborative improvement techniques will offer a cost effective, comprehensive solution that is less disruptive, reduces waste and increases accuracy, leading to high quality outcomes. The aim of this research is to develop a BIM based protocol supporting development of 'what if' scenarios in housing retrofits for high efficiency thermal improvements, aiming to reduce costs and disruption for users. The paper presents a literature review on the topic and discusses the research method for the research project (S-IMPLER)

Parameterized Synthesis Case Study: AMBA AHB (extended version)

We revisit the AMBA AHB case study that has been used as a benchmark for several reactive syn- thesis tools. Synthesizing AMBA AHB implementations that can serve a large number of masters is still a difficult problem. We demonstrate how to use parameterized synthesis in token rings to obtain an implementation for a component that serves a single master, and can be arranged in a ring of arbitrarily many components. We describe new tricks -- property decompositional synthesis, and direct encoding of simple GR(1) -- that together with previously described optimizations allowed us to synthesize the model with 14 states in 30 minutes.Comment: Moved to appendix some not very important proofs. To section 'optimizations: added the model for 0-process. Extended version of the paper submitted to SYNT 201

Information disclosure and environmental rights: the Aarhus Convention

Access to information is the first "pillar" of the Aarhus Convention on Access to Information, Public Participation in Decision-Making and Access to Justice in Environmental Matters (1998). This article examines how the information disclosure obligations on states within the Aarhus Convention express a particular blend of human environmental rights, conjoining procedural entitlements (and duties) with a substantive right to an environment adequate to human health and well-being: "Aarhus environmental rights" have been lauded for increasing citizen access to environmental information, helping to secure more transparent and accountable regulatory processes. However, the information rights are rendered inconsistent in practice by three properties: 1) the discretion accorded to Convention Parties in interpreting Aarhus rights; 2) the exclusion of private entities from mandatory information disclosure duties; and 3) the indeterminate coupling of procedural and substantive rights. These tensions reflect a structural imbalance in the articulation of Aarhus rights between social welfare and market liberal perspectives