Exception handling—A static approach

This paper presents a static approach to exception handling. The static approach is proposed as a consequence of an examination of existing language constructs for exception handling in which several trouble spots have been revealed. The static approach consists basically of one concept, namely the sequel concept. Although the sequel concept is sufficient to specify exception handling within a program, one additional concept is introduced, namely the derived definition concept that is introduced as a generalization of the derived type and generic concepts from Ada. The main advantages of the static approach are first that it is truly static as opposed to the existing language constructs in which dynamic association is used in some way or another; and, secondly, the language constructs for exception handling are simple, easy to implement and based on familiar concepts.     

A computational framework for representing authors'' courseware models*

Abstract This paper looks at some of the problems of existing courseware authoring systems, and advocates the use of knowledge-based techniques to resolve these problems and to form the basis of future authoring environments. The prototype knowledge-based representation language, GTE, is presented as an example of a knowledge-based language which might form the basis of such environments. The final part of the paper discusses some of the developments in GTE which must take place if it is to be used within a full and flexible authoring environment. The paper will focus particularly on the question of instructional strategies, but many of the observations can be taken as relevant to all the knowledge involved in a teaching interaction.     

An extensible approach to visually editing adaptive learning activities and designs based on services

Learning management systems (LMS) provide an operational environment in which an online course can be created and later executed. Inter-operation between creators and their authoring facilities, and the LMS execution engine are based on defining standards and specifications, such as the IMS Learning Design (LD). Because an LMS better serves as a course player than as a course creator, a large number of approaches and environments for standards-compliant course authoring have been developed. These approaches and environments propose a number of issues that deal with how adaptations are edited and how to define the connection of learning activities with external learning applications and services. These questions have raised concern, mostly because of the excessive commitment of the creators’ methods and tools used with an educational modeling language, as well as the isolation of the language used to describe the course from the host LMS. This work describes an abstract, extendible language used to specify the learning design of a course, which can be transformed into any LD language as required by the execution environment. The language is used from a generative authoring environment that offers the possibility of editing web services as an additional resource to assess learning activities.     

A Scalable Toolkit for Designing Multimedia Authoring Environments

This paper introduces Kaomi, a scalable toolkit for designing authoring environments of multimedia documents. The underlying concept is to provide the designer of multimedia applications with a fast method to get an authoring system based on a set of synchronized views (the presentation view for displaying the document, the scenario view for showing the temporal organization of the document, ...) so that each view is the support of editing actions. Kaomi is flexible enough to support a variety of multimedia documents declarative formats. It is indeed a scalable toolkit since it provides facilities for extending and/or for modifying the resulting authoring environment. In addition, cross-platform portability is provided which allows operation in the heterogenous Internet environment. The use of Kaomi is mainly described through the design of two authoring environments: one for authoring a sub-set of the Smil standard of the W3C and the other one for Madeus, a constraint based multimedia language.     

The HEFTI Model of Text to Hypertext Conversion

Manual authoring is a major bottleneck in the more widespread use of hypertext. The authoring process has been shown to be slow and labour intensive and hence expensive. Yet there already exists a large body of printed material which can be adopted for hypertext and hypermedia. In the project HEFTI (Hypertext Extraction From Text Incrementally), we are exploring methods of converting printed text into hypertext. We have developed a model which breaks the conversion process into a sequence of six modular components. The output of the conversion process are hypertext documents in a general specification language. In this paper we detail the model and our implementation of the HEFTI model. We believe the system demonstrates the validity of the model as it was used to convert a medium-sized technical textbook into hypertext within a (long) working day. We furthermore discuss two usability experiments that we carried out on HEFTI produced documents. In the conclusion of this paper we look at some open research issues.     

A language for inquiring about the run-time behaviour of programs

This paper describes a language for studying the behaviour of programs, based upon the data collected while these programs are executed by a computer. Besides being a useful tool in debugging, the language is also valuable in the experimental evaluation of the complexity of algorithms, in studying the interdependence of conditionals in a program and in determining the feasibility of transporting programs from one machine to another. The program one wishes to analyse is written in an Algol 60-like language; when the program is executed it automatically stores, in a data base, the information needed to answer general questions about computational events which occurred during execution. This information consists (basically) of the list of labels passed while the program is being executed, and the current values of the variables. Since the list of labels is describable by regular expressions, these expressions can also be used to identify specific subparts of the list and therefore allow access to the values of the variables. This constitutes the basis for the design of the inquiry language. The user's questions are automatically answered by a processor which inspects the previously generated data base. The paper also presents examples of the use of the language and describes the implementation of its processor.     

A language for defining spatial trusses

This paper describes a computer language enabling its users to define three-dimensional truss structures. The language can be used either as a design tool in specifying the geometrical characteristics of these structures or as an input language to a program that actually performs their structural analysis. The main characteristic of the language is that it is procedural; programs defining a nucleus of a structure can be made into procedures (subroutines) which can be called within programs and other procedures in order to define more complex structures composed of that nucleus or its variants. This characteristic is particularly useful in defining repetitive geometrical patterns which themselves appear within repetitive patterns. The paper also describes a syntax-directed compiler whose input is a sentence in the language and whose output is interpretable code which, when executed, produces drawings and provides listings of the coordinates of the points and the linkages defined by the user in his source program. Several examples of structures defined using this language are included in the paper.     

Computer-assisted instruction in engineering education and training

A computer-based economy implies a computer-based education. Learning and teaching are optimized by the student, as well as for the professor, if instructional redundancy is captured for reuse. One of the fundamental problems, to be confronted in the construction of complex learning programs, is that of providing ever higher-level authoring languages. This paper shows how instructional reuse, as mediated by a random seeded crystal learning algorithm, can facilitate the evolution of complex learning frames. A natural language interface enables the sharing of large software projects across a team. Here, a knoqledge-based system acquires a capability to map natural language phrases onto object invocations. The natural language phrases are iteratively normalized through a transformative process, which utilizes band theory. A human-machine system is described, which entails the construction of a self-referential program editor. The presented concepts and arguments are codified with examples taken from information systems and flexible manufacturing. Learning is shown to be a consequence of randomization and reuse.     

基于本体的VB语言程序设计知识表示方法研究

针对目前高校VB语言程序设计课程教学过程中存在的问题,探讨了知识库本体的概念和研究方法,设计了基于本体的课程知识构架及知识表示形式,给出了基于本体的教学资源平台建设及语义检索开发的结构描述。实验表明基于本体构建的课程知识体系模型,可以有效地表示本门课程的知识结构,有利于课程内容的资源共享和语义查询。     

The mobile programming system,Janus

Janus is a symbolic language used to embody the information which is normally passed from the analysis phase of a compiler to the code generators. It is designed for transporting software: A program coded in a high level language can be translated to Janus on one computer, and the resulting output translated to assembly code on another. (The STAGE2 macro processor could be used for the second translation.) In this paper we present the principles upon which Janus is based, and show that it is suited to a wide range of source languages and target computers.     

多媒体编著语言的设计与实现

根据基于时序逻辑和XYZ系统思想的多媒体数据描述模型,设计并实现了一种新的多媒体编著语言MAL(multimedia authoring language),该语言具有抽象描述、同步描述、逐步求精设计的描述等能力,将多媒体节目中媒体对象的建模和多媒体节目的设计过程在一个统一的框架内进行描述.以该语言实现为核心，研制了一个交互式可视多媒体编著环境.     

Combining interactivity and improved layout while creating educational software for the Web

Two major attributes influence a project aimed at developing educational software: user interactivity and graphic design. These two attributes are not easily found within the same development tool. Moreover, sometimes the development tool is either very expensive to acquire or too difficult to use. This article aims to present a solution to the creation of educational development tools which emphasize the conjunction between interactivity and graphic design. The authors propose a methodology based on Web technology and an association between the Java programming language and the authoring tool Flash. In addition to fostering interactivity, Java offers development packages at no cost. The authoring software Flash is inexpensive and allows the creation of finely crafted Web pages with graphic animations and sound editing. This article describes the methodology that enables the association between Java and Flash components. This methodology was conceived during the development of a structural analysis educational software product specially geared to undergraduate engineering students. In order to ensure the understanding of our proposal, a specific example was created, along with sample pages that illustrate this methodology.     

多媒体结构的设计与选择

构造一个上下文敏感,具有可交互性的多媒体表示远比单纯构造视听信息或者单纯构造文本信息复杂得多.多媒体对象之间的交互需要有一个用来同步和异步交互的,包括立即响应的时空关系组织起来.根据构造环境的需要来考虑多媒体的结构构造.先通过介绍影响多媒体结构构造的7个要素来认识多媒体,然后在4种典型的构造模式中进行多媒体环境的选择.这4种构造模式分别是:结构化、时间关系、图关系、脚本形式.通过各种各样的观察和分析发现,结构化的多媒体构造为多媒体的表示提供了最为有效的表示形式.     

An overview of the K semantic framework

K is an executable semantic framework in which programming languages, calculi, as well as type systems or formal analysis tools can be defined, making use of configurations, computations and rules. Configurations organize the system/program state in units called cells, which are labeled and can be nested. Computations carry “computational meaning” as special nested list structures sequentializing computational tasks, such as fragments of program; in particular, computations extend the original language or calculus syntax. K (rewrite) rules generalize conventional rewrite rules by making explicit which parts of the term they read, write, or do not care about. This distinction makes K a suitable framework for defining truly concurrent languages or calculi, even in the presence of sharing. Since computations can be handled like any other terms in a rewriting environment, that is, they can be matched, moved from one place to another in the original term, modified, or even deleted, K is particularly suitable for defining control-intensive language features such as abrupt termination, exceptions, or call/cc.This paper gives an overview of the K framework: what it is, how it can be used, and where it has been used so far. It also proposes and discusses the K definition of Challenge, a programming language that aims to challenge and expose the limitations of existing semantic frameworks.     

The S.A.G.E. Project

ABSTRACT

This paper describes the process and creation of a library resources and services Web page within WebCT, a course authoring program that is being used to deliver complete course content over the Internet in a distance education program at The Ohio State University. A librarian at the Prior Health Sciences Library was asked to join a faculty team to teach and provide library services for a series of three courses. The students are working health professionals who cannot attend regularly scheduled classes. Illustrations are included of the WebCT course page and the library resources and services page. The initial process and planning are described, and recommendations for future research are identified.     

Experience with a portable debugging tool

Debugging tools are usually highly machine and compiler dependent programs that are either impossible to move or require a tremendous effort to move to another machine. This paper describes Ctrace, a portable debugging tool for the C language that provides the same, easy-to-use debugging environment on all machines. A similar debugger can be written for any language. Ctrace is a preprocessor that inserts source language debugging code into the program before compilation that, at execution time, prints the text of each source language statement along with the values of variables it uses and modifies. Redundant trace output from program loops is detected and eliminated. Tracing can be limited to selected statements or functions. Ctrace has shown its usefulness and popularity by its installation on over 200, computers at Bell Laboratories. It has proven its portability by being used to test software on four different operating systems and nine different processors.