A programming-language extension for distributed real-time systems

In this paper we propose a method for extending programming languages that enables the specification of timing properties of systems. The way time is treated is not language specific and the extension can therefore be included in many existing programming languages. The presented method includes a view on the system development process. An essential feature is that it enables the construction of (hard) real-time programs that may be proven correct independently of the properties of the machines that are used for their execution. It therefore provides a similar abstraction from the execution platform as is normal for non-real-time languages. The aim of this paper is to illustrate the method and demonstrate its applicability to actual real-time problems. To this end we define a simple programming language that includes the timing extension. We present a formal semantics for a characteristic part of the language constructs and apply formal methods to prove the correctness of a small example program. We consider in detail a larger example, namely the mine-pump problem known from the literature. We construct a real-time program for this problem and describe various ways to map the program to an implementation for different platforms

Trade & Cap: A Customer-Managed, Market-Based System for Trading Bandwidth Allowances at a Shared Link

We propose Trade & Cap (T&C), an economics-inspired mechanism that incentivizes users to voluntarily coordinate their consumption of the bandwidth of a shared resource (e.g., a DSLAM link) so as to converge on what they perceive to be an equitable allocation, while ensuring efficient resource utilization. Under T&C, rather than acting as an arbiter, an Internet Service Provider (ISP) acts as an enforcer of what the community of rational users sharing the resource decides is a fair allocation of that resource. Our T&C mechanism proceeds in two phases. In the first, software agents acting on behalf of users engage in a strategic trading game in which each user agent selfishly chooses bandwidth slots to reserve in support of primary, interactive network usage activities. In the second phase, each user is allowed to acquire additional bandwidth slots in support of presumed open-ended need for fluid bandwidth, catering to secondary applications. The acquisition of this fluid bandwidth is subject to the remaining "buying power" of each user and by prevalent "market prices" – both of which are determined by the results of the trading phase and a desirable aggregate cap on link utilization. We present analytical results that establish the underpinnings of our T&C mechanism, including game-theoretic results pertaining to the trading phase, and pricing of fluid bandwidth allocation pertaining to the capping phase. Using real network traces, we present extensive experimental results that demonstrate the benefits of our scheme, which we also show to be practical by highlighting the salient features of an efficient implementation architecture.National Science Foundation (CCF-0820138, CSR-0720604, EFRI-0735974, CNS-0524477, and CNS-0520166); Universidad Pontificia Bolivariana and COLCIENCIAS–Instituto Colombiano para el Desarrollo de la Ciencia y la Tecnología “Francisco Jose ́ de Caldas”

Capture and Maintenance of Constraints in Engineering Design

The thesis investigates two domains, initially the kite domain and then part of a more demanding Rolls-Royce domain (jet engine design). Four main types of refinement rules that use the associated application conditions and domain ontology to support the maintenance of constraints are proposed. The refinement rules have been implemented in ConEditor and the extended system is known as ConEditor+. With the help of ConEditor+, the thesis demonstrates that an explicit representation of application conditions together with the corresponding constraints and the domain ontology can be used to detect inconsistencies, redundancy, subsumption and fusion, reduce the number of spurious inconsistencies and prevent the identification of inappropriate refinements of redundancy, subsumption and fusion between pairs of constraints.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Boundary conditions for coupled quasilinear wave equations with application to isolated systems

We consider the initial-boundary value problem for systems of quasilinear wave equations on domains of the form $[0,T] \times \Sigma$, where $\Sigma$ is a compact manifold with smooth boundaries $\partial\Sigma$. By using an appropriate reduction to a first order symmetric hyperbolic system with maximal dissipative boundary conditions, well posedness of such problems is established for a large class of boundary conditions on $\partial\Sigma$. We show that our class of boundary conditions is sufficiently general to allow for a well posed formulation for different wave problems in the presence of constraints and artificial, nonreflecting boundaries, including Maxwell's equations in the Lorentz gauge and Einstein's gravitational equations in harmonic coordinates. Our results should also be useful for obtaining stable finite-difference discretizations for such problems.Comment: 22 pages, no figure

Collaboration In Software Engineering Projects: A Theory Of Coordination

Coordination of engineering decisions is a central concern of software engineering. We present a theory in which coordination of engineering decisions is modeled as a distributed constraint satisfaction problem (DCSP). We derive six hypotheses, predicting how the distribution of decisions over developers and the density of constraints among decisions will affect development time, probability that a file contains a field defect, and developer productivity. We test these hypotheses using data from a commercial project. We find support for all hypotheses predicting detrimental effects from poor distribution of decisions over developers. The effects of constraint density were mixed, showing that dense constraints slowed development but did not significantly affect productivity. Dense data dependencies increased the chances that a file contained a field defect, but, very surprisingly, dense call dependencies significantly lowered the chances that a file contained a field defect. We discuss the implications of these findings

Usable Design of Civil Engineer Information Systems

This research used a case study methodology where one instrument used to collect data was a heuristic usability inspection method. Data was collected from a literature review of pertinent Civil Engineer information system design documents, and conclusions drawn about the existing level of specification of usability engineering principles. The heuristic usability inspection method was used to validate the conclusions drawn through inspection of an information system representative of other Civil Engineer information systems, the Automated Civil Engineer System Personnel Readiness module

Integrating Cost as an Independent Variable Analysis with Evolutionary Acquisition - A Multiattribute Design Evaluation Approach

Guidance from the Under Secretary of Defense for Acquisition, Technology, and Logistics (USD(AT&L)) requires 100 percent of defense programs to incorporate cost as an independent variable (CAIV) and evolutionary acquisition (EA) plans within their management baselines. Historically, these two concepts have been implemented independent of one another. In reality, CAIV and EA are tightly coupled, Integration of these two initiatives enables warfighters and developers to better allocate constrained resources, respond to fluctuations in program funding, and plan for future development activities. This research creates a decision tool to assist the DoD acquisition community in satisfying the intent of the USD(AT&L) guidance. Using multiattribute design evaluation techniques, a core CAIV model is formulated. Next, the core model is expanded to incorporate the dominant features of EA. The expanded model seeks to optimize overall utility across a horizon of multiple development increments. Additionally, technical risk factors are integrated to discount the realized level of attainment for design attributes. Using a DoD command and control system development as the case study, the fully formulated CAIV/EA model is implemented and in a PC spreadsheet. An optimization application solves the mathematical program for a series of cost constraints. The resulting data are collected and translated into a variety of graphics. Sensitivity analysis is performed to understand the response caused by variations in the model\u27s parameters. Model limitations are discussed and recommendations for further investigation are presented

Deconstruction and other approaches to supersymmetric lattice field theories

This report contains both a review of recent approaches to supersymmetric lattice field theories and some new results on the deconstruction approach. The essential reason for the complex phase problem of the fermion determinant is shown to be derivative interactions that are not present in the continuum. These irrelevant operators violate the self-conjugacy of the fermion action that is present in the continuum. It is explained why this complex phase problem does not disappear in the continuum limit. The fermion determinant suppression of various branches of the classical moduli space is explored, and found to be supportive of previous claims regarding the continuum limit.Comment: 70 page