This paper proposes a model for access control within object-oriented systems. The model is based on RBAC (role-based access control) and is called DRBAC (dynamic RBAC). Although RBAC is powerful in access control, the original design of RBAC required that user-role assignments and role-permission assignments should be handled statically (i.e., the assignments should be handled by human beings). Nevertheless, the following dynamic features are necessary in access control within a software system: (a) managing dynamic role switching, (b) avoiding Trojan horses, (c) managing role associations, and (d) handling dynamic role creation and deletion. DRBAC offers the dynamic features. This paper proposes DRBAC.

The increasing complexity and shorter life cycle of software have made it necessary to reuse software. Object-oriented development has not facilitated extensive reuse of software and it has become difficult to manage and understand modern object-oriented systems which have become very extensive and complex. However, components, compared with objects, provide more advanced means of structuring, describing and developing systems, because they are more coarse grained and have more domain-specific aspects than objects. In addition, they are also suited to a current distributed environment due to their reusability, maintainability and granularity. In this paper, we present a process of extracting components from object-oriented systems. We define some static metrics and guidelines that can be applied to transform object-oriented systems into component-based systems. Our process consists of two parts. First, basic components are created based on composition and inheritance relationships between classes. Second, the intermediate system is refined into a component-based system with our proposed static metrics and guidelines.

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.

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.

This paper proposes the GDV system, which provides a format-independent interface with which to access documents in various formats. It also proposes a new approach for document representation to be used in the GDV system. In this approach, a document is represented by a chain of objects, each of which belongs to a certain class and transforms access operations according to the class-specific transformation rule. A user's request is interpreted as a request to the uppermost object of the chain, transformed by objects in the chain successively, and executed by the lowermost object in the chain. The initial state of a document is an object chain containing an unidentified object. As the unidentified object identifies and divides itself, classification (and chain generation) proceeds step by step.