Using object-oriented techniques, one can build software that models the real world more closely. In objectoriented analysis and design, two types of closely interrelated models have been built which specify the static structure and the dynamic behavior of objects. Much work based on those models deals with how to use inheritance to support reuse and easy extension more precisely. In this paper, we are concerned with the dynamic aspects of objects, and define a behavior inheritance relationship between a class and its subclass. We present a set of derivation operations based on the incremental design of the behavior model. The operations preserve the behavior inheritance relationship between classes. The result makes a theoretical base for making new classes by reusing the existing classes in objectoriented system development.

A formal system-level synthesis model for the concurrent object-oriented design of parallel computer systems, called Multi-token Object-oriented Bi-directional net (MOBnet), is proposed. The MOBnet model extends the standard Petri net by defining (1) multiple tokens to represent different kinds of synthesis control information, (2) object-oriented nodes (places) to denote the system parts under synthesis, and (3) bi-directional arcs to model the design completion check and synthesis rollback operations. In this paper, we first show that MOBnet can serve as a pre-fabrication design methodology analysis tool in ways such as class hierarchy construction, design specification comparison, reachability analysis, and concurrent process management and analysis. We then formally prove MOBnet to be a valid model for concurrent synthesis and give experimental application examples to verify. Finally, solution schemes for the design completion check and synthesis rollback problems are formally validated by analyzing the dynamic behavior of MOBnet, and experimentally illustrated through examples.

In this paper, we present a first step for developing a method of verifying both safety and correctness of object-oriented design specification. At first, we analyze the discrepancies, which can occur between requirements specification and design specification, to make clear target faults. Then, we propose a new design review method which aims at detecting faults in the design specification by using three kinds of information tables. Here, we assume that component library, standards for safety and design specification obtained from the Booch's object-oriented design method are given. At the beginning, the designers construct a design table based on a design specification, and the verifiers construct a correctness table and a safety table from component library and standards for safety. Then, by comparing the items on three tables, the verifiers review a given design specification and detect faults in it. Finally, using a small example of object-oriented design specification, we show that faults concerning safety or correctness can be detected by the new design review method.

A structural active-object system (SAOS) is a transition-based object-oriented system suitable for rapid development of hardware logic simulators. A SAOS consists of a collection of interacting structural active objects (SAOs), whose behaviors are determined by the transition statements provided in their class definitions. Furthermore, SAOs can be structurally and hierarchically composed from their component SAOs like hardware components. These features allow SAOs to model components for circuit simulation more naturally than passive objects used in ordinary object-oriented programming. Also, we can easily create new kinds of components by using the inheritance mechanism. Executions of transition statements may be event-and/or time-driven, and hence digital, analog, and mixed-mode simulation is possible. Prototype simulation programs with graphical user interfaces have been developed as SAOS programs for digital, analog, and mixed-mode circuit simulation.

In this paper, we describe the design and implementation of a hypermedia system that has the following characteristics. First, being designed according to the Dexter hypertext reference model, it has a layered architecture and thus maintains commonality with other hypermedia systems based on the Dextermodel. Second, being designed based on the MHEG standard, it has data structures that are inherently suitable for data interchange and synchronization. Third, adopting the MIME protocol, it provides multimedia mail services. Finally, being built on top of an object-oriented DBMS, it makes it easy to represent Dexter and MHEG models and also provides efficient storage and search capabilities. The contribution of this paper is combining these characteristics to build an integrated hypermedia system reflecting reference architectures and international standard efforts.

A detabase system that provides step-by-step guidance for LSI failure analysts has been developed. This system has three main functions: database, navigator, and chip tracking. The datebase stores failure analysis information such as analysis method and failure mechanisms including image data. It also stores conditions and results of each analysis step and decisions to proceeds to the next analysis step. With 2000 failure analysis cases, data retrieval takes 6.6 seconds, a table containing 20 photos is presented in 6.5 seconds, and a different set of data can be displayed in 0.6 seconds. The navigator displays a standard analysis procedure illustrated in flow charts.The chip tracking shows where the particular chip is and what analysis it is undergoing, which is useful for the situation where many chips are simultaneously analyzed. Thus, this system has good enough functions of analysis procedure management and performance of quick data access to make failure analysis easier and more successful.

Aczel's theory of structured objects is extended under the assumption that a structured object may belong to a sort and that these sorts are partially ordered. Based on the assumption, the forms of required objects can be specified more precisely and concisely. The resulting theory provides a general principle for the construction of order-sorted ontologies and universes of structured objects. It is applicable to systems with structured objects, such as situation theory, feature-based grammars, knowledge representation, constraint logic programming and object-oriented systems.

We propose a distributed operation system platform for optical cable networks. This distributed platform is an extension of the previously proposed platform for a flexible cable network operation. The concept of the unit platform has been proposed for the distributed operation system platform. By using this concept, we discuss the system upgrade including the connection to other operation systems. We use an object-oriented software technology for designing the distributed operation system platform. The prototype system has been constructed using C++ programing language and the evaluated results are shown.

As Object-Oriented Database Systems (OODBS) play an increasingly important role in advanced database systems, OODBS performance becomes a significant issue. It is well known that there is a strong relationship between performance and the concurrency control algorithms employed by the Database Management System (DBMS). Class Granularity Locking (CGL) and Class Hierarchy Granularity Locking (CHGL) are proposed as the concurrency control algorithms for OODBS to minimize the locking overhead. However, their basic characteristics, including the licking overhead and concurrency, have not been extensively investigated and it is not known which one is most appropriate for the general case. In this paper, we construct a simulation model for OODBS and carry out several performance evaluation studies on these two Class-Hierarchy Locking protocols and the Non Class-Hierarchy Locking (NCL) protocol. The NCL protocal is a variation of the conventional two phase locking protocol being applied to OODBS data structures.

Flora is a functional-style language for object and relational algebra. It has been designed for efficient support of advanced database languages combining rules and objects using compilation and optimization. Flora is a strongly typed language based on an OO data model and incorporating support for collection-oriented computational capabilities. In this paper, we describe the design and architecture of the Flora optimizer which is rule-based, yet doing cost-based optimization. The optimizer uniformly captures logical, semantic and implementation knowledge regarding the execution system and the applications by means of assertions. This framework eases extensibility and enables efficient query rewriting.

In order to make the hyperling generation mechanism not only dynamic but also systematic, we will mainly describe the use of the querying and abstraction facilities in hypertext database systems. Our work focuses on a dynamic, abstract and systematic link generation mechanism. The prototype system named TextLink/Gem is implemented by taking an object-oriented approach, and the notions of anchor objects, query-pair links, polymorphic links and inheritable links, on which the system is based, and their implementations are described in detail.

For a complex object model, a form of range restriction, called specialization constraint (SC), has been studied. On the other hand, very few models have been proposed that support selective inheritance. In this paper, the following consideration is taken into SCs for a complex object medel suppoorting selective inheritance. A polynomial-time algorithm is given for deciding if a given database schema is well-formed. A sound and complete axiomatization for SCs is presented. A polynomial-time algorithm is given that decides if an SC is a logical consequence of a set of SCs. Finally, another polynomial-time algorithm is given, which decides if there exists a database that contains a given path from a given class.

This paper discusses an object-oriented approach to temporal multimedia data modeling in OMEGA; a multimedia database management under development at the University of Library and Information Science. An object-orientated approach is necessary to integrate various types of heterogeneous multimedia data, but it has become clear that current object-oriented data models are not sufficient to represent multimedia data, particularly when they are temporal. For instance, the current object-oriented data models cannot describe objects whose attribute values change time-dependently. Also, they cannot represent temporal relationships among temporal multimedia objects. We characterize temporal objects as instances of a subclass of class TimeInterval with the temporal attributes and the temporal relationships. This temporal multimedia data model is designed upward compatible with the ODMG-93 standard object model. To organize a temporal multimedia database, a five temporal axes model for representing temporal multimedia objects is also introduced. The five temporal axes--an absolute, an internal, a quasi-, a physical, and a presentation time axis--are necessary to describe time-dependent properties of multimedia objects in modeling, implementing and use. A concrete example of this organization method is also illustrated.

A typed, object-oriented database technology, equipped with appropriate declarative, temporal logic based executable constraints, is presented. The underlying object-oriented database type system is based on advanced features such as subtype, parametric and F-bounded polymorphism. A particularly distinctive feature of the type system is its associated type-safe reflection technology, which provides the flexibility required by database operators without sacrificing type safety. Strongly, and even statically typed, executable class specifications of a variety of standard database abstractions, both application-oriented and system-oriented, are presented in the paper, in order to demonstrate strate the applicability of the paradigm. The temporal logic basis of the constraint language has an execution model, as well as the minimal model semantics, and it allows complex, temporal behavioral patterns to be expressed. It is based on three tomporal operators: always, next time and some time, and rules that determine how these operators may be applied in temporal Horn clauses. Because of the object-oriented nature of the paradigm, the logic basis is also equipped with the equality predicate The proposed technology is intended to provide major advantages not only in managing appropriately complex application environments with temporal constraints, but also in providing more efficient (because of static type checking) and reliable database management systems. It offers the advantages of non-procedural data languages and the richness of a temporal object-oriented paradigm. It also leads to a powerful prototyping tool for structural and behavioral testing of complex, strongly typed object-oriented systems, prior to major procedural implementation efforts.

Object-oriented programming requires different skills from those of traditional structured programming. Thus, a good interactive environment for beginners of object-oriented programming should be provided. We have designed and implemented a visual environment of object-oriented programming for beginners. If a programmer draws a diagram of the tree of the hierarchy of classes visually by using our tool, the relationship between superclasses and subclasses are automatically established. Moreover, in order to prevent careless mistakes to override methods, the prototype environment in the Smalltalk language checks written methods. We conducted an experiment with our tool and evaluated its usefulness.

We have designed and implemented a simple yet powerful declarative synchronization mechanism for a paralle object-oriented computation model. The mechanism allows the user to control multiple message reception, specify the order of message reception, lock an invocation, and specify relations as invocation constraints. It has been included in a parallel object-oriented language, called A-NETL. The compiler and operating system have been developed on a total architecture, A-NET (Actors NETwork). The experimental results show that (i) the mechanism allows the user to model asynchronous events naturally, without losing the integrity of described programs; (ii) the replacement of the mechanism with the user's code requires tedious descriptions, but gains little performance enhancement, and certainly loses program readability and integrity; (iii) the mechanism allows the user to shift synchronous programs to asynchronous ones, with a scalable reduction of execution times: an average 20.6% for 6 to 17 objects and 46.1% for 65 objects. These prove the effectiveness of the proposed synchronization mechanism.

This paper presents a layered hierarchical switching-software technology, which is based on an object-oriented design approach, that improves software reusability and productivity. This technology enables a non-stop, service-enhanceable software environment (called NOSES), which satisfies customer demands for quick provisioning of new service features without interrupting service, and which improves software reliability. This technology was developed as part of our overall plan to establish a communications software platform that can be customized for use by various communications systems, such as STM, ATM, and IN. The developed non-stop service enhanceable software techniques are call-recovery restart, system file update, and on-line partial file modification; they were achieved by using dynamic program modification. A system file update inevitably affects calls in service, despite efforts to save in-service calls by copying the call data from the old file to the new one. We have therefore developed a different approach: on-line partial-file modification. Our prototype switching system has proven the effectiveness of this modification method and has shown that it can cover a limited range of service feature additions (which meets customer demands for quick service provisioning), as well as all bug fixes (which can lead to higher software reliability due to not using conventional machine code for software patching), without interrupting service. This paper describes on-line partial-file modification, which can be applied to communications systems that require resident program modification or initialization without program loading; that is, the program exists permanently in main memory. An evaluation of this approach also showed that the productivity of service-layer software increases about two times and that the total increase in systems development productivity is about 25%.

This paper describes the design of the reflective concurrent object-oriented specification language RMondel. RMondel is designed for the specification and modeling of distributed systems. It allows the development of executable specifications which may be modified dynamically. Reflection in RMondel is supported by two fundamental features that are: Structural Reflection (SR) and Behavioral Reflection (BR). Reflection is the capability to monitor and modify dynamically the structure and the behavior of the system. We show how the features of the language are enhanced using specific meta-operations and meta-objects, to allow for the dynamic modification of types (classes) and instances using the same language. RMondel specification can be modified by adding or modifying types and instances to get a new adapted specification. Consistency is checked dynamically at the type level as well as at the specification level. At the type level, structural and behavioral constrations are defined to preserve the conformance of types. At the specification level, a transaction mechanism and a locking protocol are defined to ensure the consistency of the whole specification.

This paper first proposes an object-oriented service network model, which is composed of application, server and resource object groups, from both viewpoints of rapid and smooth introduction and effective execution of the next generation IN services. The paper also, proposes a testbed system, which is referred to as "To-be-IN (Testbed on Object-oriented and B-ISDN Environment for IN)", for evaluating network architecture based on the proposed model. Using the testbed, several technical issues can be solved such as object-oriented realization of IN services, a provision of distribution transparent environment and a transition strategy from today's IN network. The testbed system is constructed on a currently available computing environment in which a distribution transparency mechanism is added. This system provides Service Creation Environment (SCE) for a purpose of achieving seamless software transfer from a development phase to an operation phase in the object-oriented service network model. The paper finally summarizes some results of an experimental implementation of the system.

This paper describes two main technologies for achieving reliable real-time distributed communications systems. One is the technology to prevent the influence of a fault in an autonomous distributed system from spreading to the whole system (called autonomous distributed system control). The other is a software structure based on distributed processing, the object-oriented approach, and layering for better maintainability and expandability (called OO software structure). For the autonomous distributed system control, several inter-subsystem communication methods are proposed and evaluated. From the standpoints of the fault processing and processing load, frames should be sent through a data link over ATM connection and when a fault occurs the link should be switched over without loss of data. A pilot system achieved good reliability without an excessive number of dynamic steps. This autonomous control method will lead to a highly reliable communications system with large capacity. For the OO software structure, this paper gives experimental results from the implementation of a prototype system. Its distributed environment should lead to high reliability by extending the CHILL run-time routine (RTR). This software structure promises to provide service quickly, to reduce costs, and to make the development of each layer's software independent. A real-time OS, e.g., CTRON kernel combined with RTR can give real-time performance, high reliability and high productivity over the distributed system. The use of RTR can reduce the time for the call recovery process.