基于CAN的开放式分布系统标准SDS

SDS(Smart Distribution Systems)是由Honeywell Micro Switch公司开发的一个开放式网络标准。本文主要介绍了SDS的发展背景、技术特点及其设备建模。     

Are open standards good business?

The debate about the relative merits of open vs. proprietary standards is long and ongoing. Proponents of open standards argue that they are good for society as they encourage adoption, have lower risk, and increase interoperability between technologies. On the other hand, proponents of proprietary standards maintain that monopolistic returns are justified given huge upfront and ongoing investments. While there are merits to both sides of this debate, we take a more objective approach in evaluating whether it makes sense to develop or invest in open standards. We collect investors’ reactions to Extensible Markup Language (XML) schema announcements and compare these with estimated returns for the same stock to determine whether the returns were above or below normal. We find that investors prefer proprietary XML schemas to open XML schemas by as much as 28,000%. We also find that this preference has been stable over time except in 2001 – the period of the dot com bubble burst - when investors temporarily preferred open standards. We attribute these results to two things. First, expected returns from monopoly control of proprietary standards, even though uncertain, are often worth more than those expected from open standards. Second, it seems that the markets are still unsure of the monetary benefits of open standards to the firm. Thus, companies that embrace open standards will have to better communicate to the investors the value proposition of open standards if they want to generate positive reactions on their open standardization efforts.     

An alternative definition of splicing

In this paper, we propose a new definition of the language generated by a splicing system, motivated by both biochemical and mathematical considerations. The main feature of the new definition is that by applying a splicing rule, we not only create new strings, but also allow for the removal of the strings entering the rule. This behaviour seems to correspond better to biochemical reality and is in fact used as a tool in several experimental DNA computations. We show that using this new definition, finite extended H$H$ systems can generate all recursively enumerable languages. Even a weaker version of these H$H$ systems, defined using the new notion of delay, is shown to be strictly more powerful than H$H$ systems defined in the traditional way.     

An automated,objective and open source tool for stream threshold selection and upstream riparian corridor delineation

The extraction of stream networks from digital elevation models (DEMs) and delineation of upstream riparian corridors (URCs) for stream sampling points (SSPs) are frequently used techniques in freshwater and environmental research. Selection of an accumulation threshold (AT) for stream extraction and delineation of URCs are often done manually. Two algorithms are introduced in this paper that allow for automated AT selection and URC delineation. ATs are selected to yield the highest overlap of DEM-derived and traditionally mapped streams as well as to assure extraction of all mapped streams from DEMs. URCs are delineated after snapping SSPs to DEM-derived streams. The new tool showed similar or better performance than comparable algorithms and is freely available, interfacing the open source software packages R and GRASS GIS. It will improve the extraction of stream networks and the assessment of magnitude and scale of effects from riparian stressors (e.g. landuse) on freshwater ecosystems.     

An event-based architecture definition language

This paper discusses general requirements for architecture definition languages, and describes the syntax and semantics of the subset of the Rapide language that is designed to satisfy these requirements. Rapide is a concurrent event-based simulation language for defining and simulating the behavior of system architectures. Rapide is intended for modelling the architectures of concurrent and distributed systems, both hardware and software in order to represent the behavior of distributed systems in as much detail as possible. Rapide is designed to make the greatest possible use of event-based modelling by producing causal event simulations. When a Rapide model is executed it produces a simulation that shows not only the events that make up the model's behavior, and their timestamps, but also which events caused other events, and which events happened independently. The architecture definition features of Rapide are described: event patterns, interfaces, architectures and event pattern mappings. The use of these features to build causal event models of both static and dynamic architectures is illustrated by a series of simple examples from both software and hardware. Also we give a detailed example of the use of event pattern mappings to define the relationship between two architectures at different levels of abstraction. Finally, we discuss briefly how Rapide is related to other event-based languages     

An axiomatic definition of synchronization primitives

Summary The semantics of a pair of synchronization primitives is characterized by three fundamental axioms: boundedness, progress, and fairness. The class of primitives fulfilling the three axioms is semantically defined. Unbuffered communication primitives, the symmetrical P and V operations, and the usual P and V operations are proved to be the three instances of this class. The definitions obtained are used to prove a series of basic theorems on mutual exclusion, producer-consumer coupling, deadlock, and linear and circular arrangements of communicating buffer-processes. An implementation of P and V operations fulfilling the axioms is proposed.     

An order-algebraic definition of knuthian semantics

This paper presents a formulation, within the framework of initial algebra semantics, of Knuthian semantic systems (K-systems) which contain both synthesized and inherited attributes. The approach is based on viewing the semantics of a derivation tree of a context-free grammar as a set of values, called an attribute valuation, assigned to the attributes of all its nodes. Any tree's attribute valuation which is consistent with the semantic rules of the K-system may be chosen as the semantics of that derivation tree.The set of attribute valuations of a given tree is organized as a complete partially ordered set such that the semantic rules define a continuous transformation on this set. The least fixpoint of this transformation is chosen as the semantics of a given derivation tree. The mapping from derivation trees to their least fixpoint semantics is a homomorphism between certain algebras. Thus, the semantics of a K-system is an application of the Initial Algebra Semantics Principle of Goguen and Thatcher. This formulation permits a precise definition of K-systems, and generalizes Knuth's original formulation by defining the meaning of recursive (circular) semantic specifications.The algebraic formulation of K-systems is applied to proving the equivalence of K-systems having the same underlying grammar. Such proofs may require verifying that a K-system possesses certain properties and to this end, a principle of structural induction on many-sorted algebras is formulated, justified, and applied.This paper is a revision of a paper presented at the 17th Annual IEEE Symposium on Foundations of Computer Science, Houston, Texas, October 1976. This research was supported in part by National Science Foundation Grant No. MCS 03633 A04 and by U.S. Department of Energy Contract No. EY-76-S-03-0034, PA 214.Editor's Note: This paper is one of several presented in the Session on Semantics at the 17th Annual IEEE Symposium on Foundations of Computer Science, 1976, and subsequently invited for submission to this journal to present different approaches to the subject.     

An analogue approach to surface definition

This note describes a method for producing cubic curves made up from Bézier functions on an oscilloscope screen using simple analogue techniques. Ruled surface patches are illustrated in a simple extension of the method. It also indicates how generalized Bézier patches could be produced.     

An objective representation of the Gaussian integers

A rig is a ring without negatives. We analyse the free rig on a generator x subject to the equivalence x1+x+x², showing that in it the non-constant polynomials form a ring. This ring can be identified with the Gaussian integers, which thus acquire objective meaning.     

On organisational influences in software standards and their open source implementations

ContextIt is widely acknowledged that standards implemented in open source software can reduce risks for lock-in, improve interoperability, and promote competition on the market. However, there is limited knowledge concerning the relationship between standards and their implementations in open source software. This paper reports from an investigation of organisational influences in software standards and open source software implementations of software standards. The study focuses on the RDFa standard and its implementation in the Drupal project.ObjectiveThe overarching goal of the study is to establish organisational influences in software standards and their implementations in open source software. More specifically, our objective is to establish organisational influences in the RDFa standard and its implementation in the Drupal project.MethodBy conduct of a case study of the RDFa standard and its implementation in the Drupal project we investigate organisational influences in software standards and their implementations in open source software. Specifically, the case study involved quantitative analyses of issue tracker data for different issue trackers for W3C RDFa and the Drupal implementation of RDFa.ResultsThe case study provides details on how and to what extent organisational influences occur in W3C RDFa and the Drupal implementation of RDFa, by specifically providing a characterisation of issues and results concerning contribution to issue raising and commenting, organisational involvement over time, and individual and organisational collaboration on issues.ConclusionWe find that widely deployed standards can benefit from contributions provided by a range of different individuals, organisations, and types of organisations either directly to a standardisation project or indirectly via an open source project implementing the standard. Further, we also find that open processes for standardisation adopted by W3C may also contribute to open source projects implementing specific standards.     

An objective look at C++environments

The authors evaluated six C++ environments: three for MS-DOS PCs, and three for mini and mainframe Unix systems. They tested the MS-DOS products-Advantage C++ Version 1.2 (beta2a), Guidelines C++ Version 1.2, and Zortech C++ Version 1.05-on an 8-MHz, 80286-based PC with a 44-Mbyte hard disk but with no math coprocessor. They tested Oregon C++ Version 1.1C on a Sun-3 running SunOS 3.5; GNU C++ on a Sequent Balance 21000 running Dynix 3.0; and AT&T C++ on the Sequent, the Sun, and on a Digital Equipment Corp. MicroVAX II running Unix 4.3 BSD. They believe, based on the results of their study, that C++ will be the dominant object-oriented language that industry uses for serious software development     

An axiomatic definition of the programming language PASCAL

Summary The axiomatic definition method proposed in reference [5] is extended and applied to define the meaning of the programming language PASCAL [1]. The whole language is covered with the exception of real arithmetic and go to statements.     

An operational process for goal-driven definition of measures

We propose an approach (GOM/MEDEA) for defining measures of product attributes in software engineering. The approach is driven by the experimental goals of measurement, expressed via the GQM paradigm, and a set of empirical hypotheses. To make the empirical hypotheses quantitatively verifiable, GQM/MEDEA supports the definition of theoretically valid measures for the attributes of interest based on their expected mathematical properties. The empirical hypotheses are subject to experimental verification. This approach integrates several research contributions from the literature into a consistent, practical, and rigorous approach.     

An integrated collection of software engineering standards

The IEEE Software Engineering Standards Committee has taken deliberate steps to unify and integrate its collection of software engineering standards. Encouraging results are apparent in its latest publication, which is organized around a single architecture for the SESC collection. This article explains the principles of the SESC collection and describes our progress toward integrating the various standards within it     

On an open problem related to the strict local minima ofmultilinear objective functions

This paper gives a combinatorial proof of a “yes” answer to an open question presented by Vidyasagar (ibid. vol.40, 1995), stated as follows: “Given a multilinear polynomial E(x): [0, 1] ⁿ→ℛ, is it true that E_b(x)=E(x)-b^t x has a strict local minimum over the discrete set {0, 1}ⁿ for almost all b of sufficiently small norm?” The given combinatorial proof is completed directly by providing a sufficient condition for a conjecture on the strict local minima of multilinear polynomials, also postulated in Vidyasagar, to hold. In addition, a simple counter-example is presented to demonstrate that the conjecture may be not true if the provided sufficient condition is not satisfied