Modular Object Research Articles

Upgrading a TEXTOR Data Acquisition system for remote participation using Java and Corba

The partners in the Trilateral Euregio Cluster (TEC) are implementing and developing Remote Participation technologies that are expected to support a joint research programme on the experimental facility TEXTOR-94. A common TEC architecture for our heterogeneous data acquisition and storage systems is seen to be one of the major issues. As a consequence, legacy systems will be affected and have to be upgraded for optimised wide area network communication, platform independent data access and display. The object oriented redesign of the system to be described follows theses guidelines. The architecture of the system under development uses Java as programming environment and CORBA as Client/Server communication standard. It is described in this paper, how an operational Data Acquisition CAMAC subsystem of TEXTOR-94 based on OpenVMS and Decnet communications could be redesigned into an open, object oriented architecture in a platform independent way. A suitable Web Browser is required on the client side without further installation of application software to run the server. CORBA static method invocations are used for the communication between the client and server. At the server side, there is only Java code on top of the existing commercial OpenVMS CAMAC device driver. A modular object oriented software design permitted to eliminate dependencies of the generic module levels from the underlying bus systems. Porting of the Java code to other platforms like Windows NT and Linux has proven to be successful.

A complex ligase ribozyme evolved in vitro from a group I ribozyme domain.

Like most proteins, complex RNA molecules often are modular objects made up of distinct structural and functional domains. The component domains of a protein can associate in alternative combinations to form molecules with different functions. These observations raise the possibility that complex RNAs also can be assembled from preexisting structural and functional domains. To test this hypothesis, an in vitro evolution procedure was used to isolate a previously undescribed class of complex ligase ribozymes, starting from a pool of 10(16) different RNA molecules that contained a constant region derived from a large structural domain that occurs within self-splicing group I ribozymes. Attached to this constant region were three hypervariable regions, totaling 85 nucleotides, that gave rise to the catalytic motif within the evolved catalysts. The ligase ribozymes catalyze formation of a 3',5'-phosphodiester linkage between adjacent template-bound oligonucleotides, one bearing a 3' hydroxyl and the other a 5' triphosphate. Ligation occurs in the context of a Watson-Crick duplex, with a catalytic rate of 0.26 min(-1) under optimal conditions. The constant region is essential for catalytic activity and appears to retain the tertiary structure of the group I ribozyme. This work demonstrates that complex RNA molecules, like their protein counterparts, can share common structural domains while exhibiting distinct catalytic functions.

Stochastic coupling for von Neumann algebras

We consider even and odd stochastic transitions of von Neumann algebras when dual mappings intertwine (couple) modular groups of the corresponding states (with the occurrence of a sign exchange for the odd case). We show that one can define modular objects and cones associated to linear combinations of von Neumann algebras, which generalize objects and cones in the standard modular theory. In the odd case, we find sufficient conditions for the intertwining property and consider several applications to noncommutative Markov processes.

Jonathan: an open distributed processing environment in Java

This paper describes a minimal and modular Object Request Broker (ORB) framework from which it is possible to build highly flexible ORBs supporting the introduction of arbitrary binding mechanisms between interacting objects. We show that such a framework consists essentially of extending the Java notion of object reference to make it distributed. Jonathan is a Java implementation of such a framework, featuring a CORBA 2.0 `personality' and several different binding factories. It could be easily extended with new binding factories and personalities (e.g. a RMI personality) or scaled down to fit particular needs.

A Core Calculus of Classes and Objects

We present an imperative calculus for a class-based language. By introducing classes as the basic object-oriented construct in a λ-calculus with records and references, we obtain a system with an intuitive operational semantics. Objects are instantiated from classes and represented by records. The type system for objects uses only functional, record, and reference types, and there is a clean separation between subtyping and inheritance. We demonstrate that the calculus is sound and sufficiently expressive to model advanced language features such as inheritance with method redefinition, multi-level encapsulation, and modular object construction.

Validating the TEMAA LE evaluation methodology: a case study on Danish spelling checkers

This paper describes the work carried out at the Center for Sprogteknologi in Copenhagen to validate the LE evaluation methodology developed by the LRE project TEMAA. TEMAA has developed a framework for the evaluation of LE products, implemented in a Parameterisable Testbed (PTB). The framework allows for a modular, formal and exible description of user requirements and objects of evaluation, it accommodates test methods of various kind and provides a methodology for assessing test results in the light of the requirements expressed by different user types. While the fundamentals of the TEMAA framework are meant to apply to adequacy evaluation of LE products in general, a detailed methodology has been worked out for the evaluation of spelling and grammar checkers, and applied to the concrete evaluation of Danish and Italian spelling checkers. The main focus of this paper is on showing that the general methodology provides a valid model for designing and carrying out a concrete evaluation, as in the case study on Danish spelling checkers.

Object Orientation in Educational Software

SUMMARY Changing educational circumstances and improving technology are generating the need for a unified perspective of course design that applies to computer‐based courses and courseware. It should combine the principles of educational theory, employed in conventional teaching and learning, with programming methodology, to produce a framework that is compatible with both fields. In particular, it is interesting to see what advantages can be obtained from the use of object orientation, which has proved to be successful in other computing applications. An object‐oriented model is developed which combines the principles of course design with programming practice. It produces a hierarchical structure of modular objects, each of which combines syllabus content and educational methods in a self‐contained program. The structure has a number of advantages, in terms of programming, and some specific characteristics that may be regarded as educational advantages, compared to the more traditional, procedural approach.

A comprehensive approach to method validation based on object technology

Method validation procedure requires a strategy for collecting those validation data that are best adapted to the analytical technique used. A flexible and general approach based on Object Linking and Embedding technology is proposed. It allows a traceable validation strategy using modular objects which encapsulate documentation, analytical data and processing logic. The contents of these objects are accessible through a standard user interface. This paper demonstrates how this can reduce experiment time, simplify evaluation efforts, and increase the ease of use of validation figures of merit. An illustration using Microsoft Visual Basic for Applications is presented, and some specific aspects are described. It consists of the evaluation of a time domain NMR technique for determining the moisture content of foods involving a multivariate calibration step. This study also illustrates how guidelines such as Good Validation Practices could be defined to present all validation documents in a standardised manner.

Object-Oriented Analysis of South Florida Hydrologic Systems

Object-oriented analysis is a methodology used to study real-world systems by identifying system components and behavior. An object-oriented analysis of south Florida hydrologic systems was conducted to determine how well this methodology organizes system information. The principal products of this analysis were three conceptual models characterizing the overall structure, behavior, and functionality of south Florida hydrologic systems. The object model identifies system components, or classes, their attributes, and their relationships with one another. The dynamic model presents class behavior, and the functional model shows how class attribute values are transformed. These models represent a variety of south Florida hydrologic systems and can be used to develop design specifications for a library of modular software objects, in which each object corresponds to a class in the object model.

Embedded system specifications and transformation into Occam

One of the most important stages in the development of any real-time system is the generation of a consistent design that satisfies an authoritative specification of requirements. Management of the development of complex real-time systems requires the appropriate level of decomposition, encapsulation and abstraction, and their implementation requires languages incorporating concurrency and error-handling facilities. This paper shows that Modular Object Oriented Notation (MOON) specifications cater for the specification of real-time systems, which can be suitably transformed for concurrent implementation using Occam and similar languages.

Oberon-2 in Windows: what price compatibility?

A compiler has been developed so that programs can be written in the modular object oriented language Oberon-2 for the Windows 3 environment. To assess the price of making the Oberon-2 compiler compatible with Windows 3 the relative value of several factors compared with the original ETH Oberon compiler have been measured. In summary, compiler size increased by 70%, its compile speed dropped by 40%, runtime speed dropped by 50% and project time was twice that expected.