Scattered versus context-sensitive rewriting

Summary We study the relationship between scattered and context-sensitive rewriting. We prove that an extended version of scattered grammars produces exactly the context-sensitive languages. Also unordered scattered context languages are a proper subset of scattered context languages, and unordered scattered rewriting with erasing does not generate all scattered context (and thus not all context-sensitive) languages.Part of this research was done while this author visited the Hebrew University and was supported by the Leibniz Center     

Making XML document markup international

In name and in practice, the World‐Wide Web (hereafter Web) is used around the World beyond English‐speaking areas. This creates a tremendous need to internationalize standard terminology used in the technologies that make the Web possible. Existing efforts on XML internationalization (i18n) and localization (i10n) have focused on the content of XML documents instead of the terms used in markup (annotations) such as elements and attributes. The SGML standard ISO 8879 supports the use of Unicode (ISO 10646) throughout a document, including markups. However, most elements and attributes of XML documents are still defined in English, thereby limiting their use among non‐English speakers. This paper presents an XSLT‐based method that can completely localize the markup of XML documents into different natural languages. We also describe how the proposed technique can be applied to translation problems in programming (e.g. C and Java) or documentation (e.g. LAT_EX or other formatting languages) so that a program or a document can be converted to and from an XML format. Copyright © 2004 John Wiley & Sons, Ltd.     

Multicode: a truly multilingual approach to text encoding

Unicode was designed to extend ASCII for encoding text in different languages, but it still has several important drawbacks. Multicode addresses many of Unicode's drawbacks and should have considerable appeal to programmers who work with text in a variety of languages. Its future, however, depends on the computer industry's acceptance. Multicode can represent Unicode files because it reserves a character set for Unicode. Converting Multicode to Unicode is also straightforward (although the opposite is not). Thus, both approaches can coexist-Multicode for programming ease and Unicode to support unified fonts     

Computationally Efficient Algorithm For Frequency‐Weighted Optimal H∞ Model Reduction

In this paper, a frequency‐weighted optimal H_∞ model reduction problem for linear time‐invariant (LTI) systems is considered. The objective of this class of model reduction problems is to minimize H_∞ norm of the frequency‐weighted truncation error between a given LTI system and its lower order approximation. A necessary and sufficient solvability condition is derived in terms of LMIs with one extra coupling rank constraint, which generally leads to a non‐convex feasibility problem. Moreover, it has been shown that the reduced‐order model is stable when both stable input and output weights are included, and its state‐space data are given explicitly by the solution of the feasibility problem. An efficient model reduction scheme based on cone complementarity algorithm (CCA) is proposed to solve the non‐convex conditions involving rank constraint.     

Optimization schemas for parallel implementation of non‐deterministic languages and systems

Naive parallel implementation of non‐deterministic systems (such as a theorem proving system) and languages (such as logic, constraint, or concurrent constraint languages) can result in poor performance. We present three optimization schemas, based on flattening of the computation tree, procrastination of overheads, and sequentialization of computations that can be systematically applied to parallel implementations of non‐deterministic systems/languages to reduce the parallel overhead and to obtain improved efficiency of parallel execution. The effectiveness of these schemas is illustrated by applying them to the ACE parallel logic programming system. The performance data presented show that considerable improvement in execution efficiency can be achieved. Copyright © 2001 John Wiley & Sons, Ltd.     

Workload characterization of JVM languages

Originally developed with a single language in mind, the JVM is now targeted by numerous programming languages—its automatic memory management, just‐in‐time compilation, and adaptive optimizations—making it an attractive execution platform. However, the garbage collector, the just‐in‐time compiler, and other optimizations and heuristics were designed primarily with the performance of Java programs in mind. Consequently, many of the languages targeting the JVM, and especially the dynamically typed languages, are suffering from performance problems that cannot be simply solved at the JVM side. In this article, we aim to contribute to the understanding of the character of the workloads imposed on the JVM by both dynamically typed and statically typed JVM languages. To this end, we introduce a new set of dynamic metrics for workload characterization, along with an easy‐to‐use toolchain to collect the metrics. We apply the toolchain to applications written in six JVM languages (Java, Scala, Clojure, Jython, JRuby, and JavaScript) and discuss the findings. Given the recently identified importance of inlining for the performance of Scala programs, we also analyze the inlining behavior of the HotSpot JVM when executing bytecode originating from different JVM languages. As a result, we identify several traits in the non‐Java workloads that represent potential opportunities for optimization. © 2015 The Authors. Software: Practice and Experience Published by John Wiley & Sons Ltd.     

Advantages of online spellchecking: a Croatian example

Online spellchecking is commonly regarded as an auxiliary way of performing spellchecking. However, it offers a unique opportunity to constantly improve spellchecker linguistic functionality through interaction with the community of spellchecker users. Such a possibility is crucial for spellchecking in non‐central and under‐resourced languages, in order to overcome gaps in NLP tools between them and central languages. The paper describes Hascheck, a Croatian online spellchecker able to learn words from texts it receives. It started as the first Croatian spellchecker, hence as a basic NLP tool for an under‐resourced language, but due to its learning ability it demonstrates linguistic functionality comparable to that of conventional central‐language spellcheckers. Based on these experiences we also discuss the future of online spellchecking in the context of global NLP tasks. Copyright © 2010 John Wiley & Sons, Ltd.     

A Constructive Globally Convergent Adaptive Speed Observer For Port‐Hamiltonian Mechanical Systems with Non‐Holonomic Constraints

This paper presents an adaptive speed observer for general port‐Hamiltonian mechanical systems with non‐holonomic constraints in the presence of unknown friction forces and constant disturbances. Unlike the observers recently reported in the literature, which have been designed either under the assumptions of no friction and the absence of disturbances or for a specific class of mechanical systems with the requirement of an explicit solution of certain Partial Differential Equations (PDEs) that cannot be derived a priori, this observer proposes a design that obviates the solution of PDEs and ensures global convergence for general mechanical systems with k‐non‐holonomic constraints. The observer is totally constructive and given by explicit expressions. The simulation results testify to the effectiveness and the robust features of the developed observer.     

Multipass precedence analysis

Summary This paper defines a hierarchy of languages which is properly contained in the context sensitive languages and which starts with the context free family. The hierarchy is defined inductively by controlling labeled linear grammars with languages in one family to yield languages in the next larger family. The families of the hierarchy have properties analogous to those of the context free family, in particular, the new mechanism introduced is very suitable for parsing.A language in the n-th family is specified by a sequence of n — 1 labeled linear grammars and a context free grammar. By assuming that the reversals of the first n — 1 grammars and the last labeled linear grammar are precedence grammars, the concepts and parsing algorithm of Wirth and Weber extend to yield a parsing algorithm within the hierarchy. This considerably enhances the usefulness of the construction and allows much of the power of the context sensitive languages to become accessible in measured amounts for potential programming applications.     

Transition from national standards to Unicode: multilingual support in operating systems and programming languages

Character sets are one of the basic issues for information interchange. Most current national standard character sets extend 7‐bit ASCII. These extensions conflict with each other and make the design of multilingual information systems complicated. Unicode or the Universal Character Set (UCS) is a character set that covers symbols in the major written languages. Text files and strings usually have no header to indicate which character set is in use, and they currently use one of the national standards by default. The transition from national standards to Unicode may take a longer time than expected. This paper presents the following methods to help the transition. (1) A text file format of fixed‐width characters: if the first character in a text file is a nonzero control code, the file is in UCS; otherwise, it is in the default national standard. The control code indicates which UCS subset or byte order is in use. (2) A tagged string storage: each string has a tag representing which character set or coding format is in use, e.g., the default national standard, 8‐bit subset of UCS‐2, UCS‐2, or UCS‐4. (3) A method for assigning the format of string literals: all string literals use the same syntax notation, and their storage format is the same as that of their source files. These methods can improve multilingual support without introducing much complexity. Copyright © 2000 John Wiley & Sons, Ltd.     

A page‐shift transformation format of ISO 10646

ISO 10646 Universal Character Set (UCS) or Unicode covers symbols in most of the World's written languages. There are various UCS transformation formats (UTF). UTF‐8 is compatible with systems that assume 8‐bit characters. One of the problems with UTF‐8 is its space efficiency. For files containing most Asian characters such as Han ideographs, the file sizes increase by about 50% by using UTF‐8. Although the Standard Compression Scheme for Unicode (SCSU) can compress Unicode strings to the size of a locale‐specific character set, it is complicated and is not intended to serve as a general purpose interchange format. This paper proposes a page‐shift transformation format of ISO 10646, called UTF‐S. There are four pages: 1‐byte, 2‐byte, 3‐byte and 4‐byte. Shift to page 0 uses a special code ; shift to page 1, 2, and 3 uses ISO 2022 shift codes SO, SS2, and SS3, respectively. We test several text files and compare these UTF with Big5, a locale‐specific character set. The result shows that the space efficiency of UTF‐S is better than that of UTF‐16 and UTF‐8 and is close to that of SCSU. UTF‐S is suitable for replacing locale‐specific character sets with ISO 10646 in Internet applications, such as the World Wide Web. Copyright © 2001 John Wiley & Sons, Ltd.     

中国多民族文字信息处理中的Unicode编程

随着我国经济及信息技术的高速发展,少数民族文字处理信息化和数字化的迫切性日益突出.依据合作项目“MDL”,结合各少数民族文字特点,对编码字符集选择、Unicode编程以及CodePage映射Unicode字符编码转换进行了详细论述.Unicode编程技术和文字代码转换是少数民族文字处理的基础,同时也是“MDL”实现全文检索的关键.“MDL”的建立,将对我国少数民族语言文字数字图书馆起到重要作用.     

Stretching letter and slanted‐baseline formatting for Arabic,Hebrew, and Persian with ditroff/ffortid and dynamic PostScript fonts

This paper describes an extension to ditroff/ffortid, a system for formatting bi‐directional text in Arabic, Hebrew and Persian. The previous version of the system is able to format mixed left‐to‐right and right‐to‐left text using fonts with separated letters or with connecting letters and only connection stretching, achieved by repeating fixed‐length baseline fillers. The latest extension adds the abilities to stretch letters themselves, as is common in Arabic, Hebrew and Persian calligraphic printing, and to slant the baselines of words, as is common in Persian calligraphic printing. The extension consists of modifications in ffortid that allow it to interface with (1) dynamic PostScript fonts to which one can pass to the outline procedure for any stretchable and/or connected letter, parameters specifying the amounts of stretch for the letter itself and/or for the connecting parts of the letter, and (2) PostScript fonts whose characters are slanted so that merely applying show to a word ends up printing that entire word on a single slanted baseline. As a self‐test, this paper was formatted using the described system, and it contains many examples of text written in Arabic, Hebrew and Persian. Copyright © 1999 John Wiley & Sons, Ltd.     

面向新疆双语教学的远程教学系统的设计与实现

新疆是多民族的自治区,使用的主要民族语言文字有汉语和维吾尔语,考虑到这个特殊性,在深入研究国内优秀远程教学软件的基础上,本文提出了面向新疆双语教学的维汉双语远程教学系统的总体框架,分析了维汉双语远程教学系统的体系结构以及模块功能,论述了该系统主要模块中支持维汉双语、系统界面双语显示与切换等关键技术的实现。     

Adaptability mechanisms for autonomic system implementation with AAOP

This paper presents a new approach to implementing an adaptability loop in Autonomic Computing (AC) systems, which is based on adaptable aspects. The approach utilizes the concept of adaptable aspect‐oriented programming (AAOP) in which a set of AOP aspects is used to run an application in the manner specified by its adaptability strategy. We present a model execution environment based on this concept, enabling the execution of applications with applied adaptability strategies. In the AAOP‐based AC system, the application is instrumented with aspects selected by the system from a set of all available aspects (sensors, effectors, and goal aspects) in such a way that the system can monitor and manage the application. This model can be used to implement systems that are able to monitor an application and its execution environment, and perform actions such as changing the current set of non‐functional constraints in response to changes in the application or its environment. The model can be used for various types of non‐functional goals, in various programming languages, both in centralized and distributed environments. This paper describes its Java‐based implementation and non‐functional goals referring to resource management. As a consequence, the application uses resources in a way specified in its adaptability strategy. Resource consumption management logic is transparent for the application, meaning that no modifications in the application source code are needed. Copyright © 2010 John Wiley & Sons, Ltd.     

On non context-free grammar forms

A grammar formF defines via a so-calledinterpretation mechanism, a family of languages(F). In this paper we establish that for many grammar formsF, (the family of context-free languages) implies(F)= _RE (the family of recursively enumerable sets). We conjecture that this is also true in general. Because of this, it seems necessary to use restricted interpretations for non context-free grammar forms, a form giving then rise to a family We compare the obvious alternatives for restricting interpretations and focus attention on two promising alternatives, _Q (_F) and _st(F) and their combination _{Q, st}(F). Using st-interpretations, surprising families can be generated and strong normal form results can be obtained. Closure results and decidability results are also given. UnderQ, st-interpretation, it is possible to characterize a number of well-known families of languages between _CF and _RE, including the families of EOL, ETOL, matrix and scattered context languages.Part of this work was carried out while the third and fourth authors were visiting the University of Karlsruhe. Part of this work was supported by the Natural Sciences and Engineering Research Council of Canada Grant No. A-7700.     

An implementation of precompiled headers

Compilation time can be improved by precompiling interfaces so that the compiler can avoid processing unreferenced declarations. However, in C-based languages precompiling a header is difficult because a header can have several meanings depending on the context in which it is included. We present an ad hoc solution to this problem, and give the results of our precompilation strategy, which improved compile times by 25 to 65 per cent over compilation without precompiled headers.