Architecture-Directed Refinement

As critical computer systems continue to grow in complexity, the task of demonstrating that they are correct, that is, guaranteed to operate without failure, becomes more difficult. For this reason, research in software engineering has turned to formal methods, i.e. rigorous approaches to demonstrating the correctness of software systems. Unfortunately, the formal methods currently used for concurrent systems do no provide a mechanism for expressing and manipulating non-functional constraints formally. In this paper, we show that one class of non-functional constraints, the target architectures, can be expressed using formal notation (the UNITY proof logic). We then use a mixture of specifications and program refinements to derive a program which is demonstrably correct, both functionally and in its appropriateness for implementation on a specific machine

Reasoning about Places, Times, and Actions in the Presence of Mobility

The current trend toward portable computing systems (e.g., cellular phones, laptop computers) brings with it the need for a new paradigm for thinking about designing distributed applications. We introduce the term mobile to refer to distributed systems that include moving, autonomous agents which loosely cooperate to accomplish a tastk. The fluid nature of hte interconnections between components in a mobile system provides new challenges and new opportunities for the research community. While we do not propsoe to have fully grasped the consequences of these systems, we believe that the notions of place, time, and action will be central in any model that is developed. In this paper, we show that these concepts can be expressed and reasoned about in the UNITY logic with a minimal amount of additional notation. We choose as an example an elevator control system, with minor modifications to give the system mobile characteristics. We begin with a high-level specification of the control system, one which does not include any mobile characteristics, and introduce the notions of place, time, and action as they arise in the specification refinement process. The result of the refinement is an abstract program, a specification of the local actions of the system along with restrictions on teh cooperation patterns between the various components

Swarm Language Reference Manual

This document contains a description of the grammar and syntax rules of the Swarm programming language. This language, which is an implementation of the program specification language used with the Swarm computational model, is used both to specify programs and their visualizations, for the use of the Pavane program visualization system

SwarmExec: A Prolog-Based Execution Engine for a Shared-Database Language with Visualization Capabilities

We have implemented a Prolog execution engine for the shared-database language Swarm extended with visualization capabilities. We call this execution engine SwarmExec. SwarmExec runs on a Macintosh Iifx under Advanced A.I. Systems\u27 Prolog (AAIS) and communicates over an Ethernet connection with a Silicon Graphics Personal Iris which serves as a graphical engine and renders the visualizations. This paper describes the major design elements of SwarmExec. A basic familiarity with Swarm and its visualization extensions is assumed; the interested reader is referred to the referenced papers

On Deriving Distributed Programs from Formal Specifications of Functional Requirements and Architectural Constraints

This design of distributed programs is a difficult task which can greatly benefit from the application of formal methods. Since design solutions are determined not only by functional requirements imposed by the application but also by the structure and behavior of the underlying hardware architecture, a complete formal treatment of the program derivation process becomes a significant challenge. The common approach is to state with a formal specification of the functional requirements and to derive the desired program through systematic refinements which factor in the architectural constraints informally, in an ad-hoc manner. This paper shows how one can employ a single specification method (program0wide assertions) to express both functional requirements and architectural constraints. A distributed simulation problem is used to illustrate a formal strategy for deriving a distributed program from assertions about its functionality and the constraints imposed by the choice of underlying architecture

Measurement of [OIII] Emission in Lyman Break Galaxies

Measurements of [OIII] emission in Lyman Break galaxies (LBGs) at z>3 are presented. Four galaxies were observed with narrow-band filters using the Near-IR Camera on the Keck I 10-m telescope. A fifth galaxy was observed spectroscopically during the commissioning of NIRSPEC, the new infrared spectrometer on Keck II. The emission-line spectrum is used to place limits on the metallicity. Comparing these new measurements with others available from the literature, we find that strong oxygen emission in LBGs may suggest sub-solar metallicity for these objects. The [OIII]5007 line is also used to estimate the star formation rate (SFR) of the LBGs. The inferred SFRs are higher than those estimated from the UV continuum, and may be evidence for dust extinction.Comment: 25 pages, including 6 figures. Accepted for publication in Ap

Experimental Sonic Boom Measurements on a Mach 1.6 Cruise Low-Boom Configuration

A wind tunnel test has been conducted by Gulfstream Aerospace Corporation (GAC) to measure the sonic boom pressure signature of a low boom Mach 1.6 cruise business jet in the Langley Unitary Plan Wind Tunnel at Mach numbers 1.60 and 1.80. Through a cooperative agreement between GAC and the National Aeronautics and Space Administration (NASA), GAC provided NASA access to some of the experimental data and NASA is publishing these data for the sonic boom research community. On-track and off-track near field sonic boom pressure signatures were acquired at three separation distances (0.5, 1.2, and 1.7 reference body lengths) and three angles of attack (-0.26deg, 0.26deg, and 0.68deg). The model was blade mounted to minimize the sting effects on the sonic boom signatures. Although no extensive data analysis is provided, selected data are plotted to illustrate salient features of the data. All of the experimental sonic boom pressure data are tabulated. Schlieren images of the configuration are also included

Correct Social Usage Volume 1: A Course of Instruction in Good Form Style and Deportment by Eighteen Distinguished Authors

The preface of the volume says that, This course of instruction sums up for its readers the substance of the truest good form. It teaches society\u27s customs intelligently, it treats society topics thoroughly, it offers helps for social perplexities. In the scope of its subject matter it includes everything which could rightly be placed between the covers of a practical work on etiquette, while in the unique manner of presenting this matter it has accomplished something never attempted before. This volume is organized into three books: Social Self-Culture, Everyday Etiquette, and Conventional Requirements, each with several essays by an individual author. The book about Social Self-Culture provides general discussion of good manners and etiquette in society. Everyday Etiquette gives more specific advice for various social occasions, such as conversation, table etiquette, correspondence and gifts. Conventional Requirements provides guidelines for such social situations as introductions, calls, and visiting cards.https://openworks.wooster.edu/motherhomeheaven/1091/thumbnail.jp

Submersed Aquatic Vegetation in Chesapeake Bay: Sentinel Species in a Changing World

Chesapeake Bay has undergone profound changes since European settlement. Increases in human and livestock populations, associated changes in land use, increases in nutrient loadings, shoreline armoring, and depletion of fish stocks have altered the important habitats within the Bay. Submersed aquatic vegetation (SAV) is a critical foundational habitat and provides numerous benefits and services to society. In Chesapeake Bay, SAV species are also indicators of environmental change because of their sensitivity to water quality and shoreline development. As such, SAV has been deeply integrated into regional regulations and annual assessments of management outcomes, restoration efforts, the scientific literature, and popular media coverage. Even so, SAV in Chesapeake Bay faces many historical and emerging challenges. The future of Chesapeake Bay is indicated by and contingent on the success of SAV. Its persistence will require continued action, coupled with new practices, to promote a healthy and sustainable ecosystem

Long-term Annual Aerial Surveys of Submersed Aquatic Vegetation (SAV) Support Science, Management, and Restoration

Aerial surveys of coastal habitats can uniquely inform the science and management of shallow, coastal zones, and when repeated annually,theyrevealchangesthatareotherwisedifficulttoassess fromground-basedsurveys.Thispaperreviewstheutilityofalongterm(1984–present)annualaerialmonitoringprogramforsubmersedaquaticvegetation(SAV)inChesapeakeBay,itstidaltributaries, and nearby Atlantic coastal bays, USA. We present a series of applications that highlight the program’s importance in assessing anthropogenic impacts, gauging water quality status and trends, establishing and evaluating restoration goals, and understanding the impactofcommercialfishingpracticesonbenthichabitats.Theseexamplesdemonstratehowperiodicallyquantifyingcoverageofthis important foundational habitat answers basic research questions locally, as well as globally, and provides essential information to resource managers. New technologies are enabling more frequent and accurate aerial surveys at greater spatial resolution and lower cost. These advances will support efforts to extend the applications described here to similar issues in other areas