Takaichi Yoshida

The flying object for an open distributed environment

We propose the flying object that adapts itself to the environment by means of a dynamic behavior change mechanism. The flying object is a user-defined, first-class and abstract entity. Such properties provide independency and transparency. The flying object model establishes a unique decomposition of the flying object. In this model, the flying object consists of four objects: the delegater that encapsulates the implementation, the message handler that interprets the messages, the event handler that provides adaptation strategies and the context object that holds a state beyond the adaptation. The ability of accommodation, the openness, is one of the great contributions of this model because many functions such as object migration, load balancing, distributed transaction management, the communication protocols and even adaptation strategies can be introduced by the message handler and the event handler as a plug-in module. Furthermore, a source code translation technique is introduced for automatic decomposition of the flying object as a replacement for the virtual machine customizations or low-level programming. The delegater and the context object are instantiated from the same translated class to minimize maintenance costs of classes as a result of an automatic translation. Therefore, the system organized by the flying object is best suited for the open distributed environment.

An adaptable replication scheme for reliable distributed object-oriented computing

To enhance reliability of distributed systems, replication techniques are used. We propose an adaptable replication scheme that enables an object to adapt itself to provide a replicated service, and a replicated object to choose the replication strategy that best fits to achieve its requirements. What kind of replication strategy should be used depends on an execution environment as well as an application. The adaptable replication scheme permits replacement of down replicas, or change of the number of replicas when partial failures occur and chooses the most adequate consistency protocol for the current configuration. Clients to the recently adapted objects for replication should take actions that enables then to obtain a thorough service of the replicated object. The adaptable replication scheme is being designed as part of the Juice system. The Juice object model allows objects to change its behavior on the fly by replacing some components in a modular way.

Route navigation method for disabled access GIS in consideration of abilities and psychologies

This paper aims to propose a route navigation method for disabled access GIS. We focused the disabled’s psychologies as well as their physical conditions. This paper represents quantization of physical and psychological burden of the disabled persons inflicted by various barrier factors. Also it represents estimation of total burden of a route to determine the optimum route. The route is represented by graph theory and route navigation method which is based on Dijkstra algorithm is applied. We extend the algorithm to make it possible to provide information on obstacles even when there are no accessible routes available to destination. The result of this study is being implemented and published as 3D Web Disabled Access GIS.

Integrating OO road network database, cases and knowledge for route finding

Finding a good route for travelling has been a necessity of human beings and also one of the major problems faced by the transportation industry. The huge and complicated road network in a modern country makes it difficult to find a best route for travelling from one place to another. In Network Theory (NT) it is called the shortest path problem. Shortest path algorithms are used for solving this type of problems. The route searched by the shortest path algorithm alone may be a shortest one but could not be guaranteed as a best route because many irrelevant/unusable road segments may be the part of the solution. Moreover, these algorithms search whole road network blindly even for source and destination nodes in a small part of the road network. This imposes stringent requirements on arrangement of road network data in such a way that its retrieval, especially a part of the road or road sub-network in a specific part of the country, should be efficient and unnecessary data processing is avoided. We also observe that there are some routes that may be computed once and stored as cases for future use. This is case-based reasoning (CBR) that is a recent approach to problem solving and learning. In this paper we integrate Objectoriented Road Network Database, CBR and knowledge to reduce the search space and time for a shortest route finding algorithm.

OORF: an object-oriented route finder

Travelling is a part of human beings day-to-day life. The huge and complicated road network in a country makes it difficult to find a shortest (best) route for travelling from one place to another. Many shorts route finding algorithms have been designed. Since route finding involves a massive and complicated road network data therefore, it is necessary to arrange the data in such a way that its retrieval, especially a part of the road or road sub-network in a specific part of the country, should be efficient and unnecessary data processing is avoided. This paper presents an object-oriented road network data model in which we divide the road into road segments and road network into road sub-networks, into levels in which a country is divided administratively, i.e. prefectures, cities, etc. We have implemented the model for shortest route finding.

A quorum based group k -mutual exclusion algorithm for open distributed environments

This paper presents a quorum-based group k-mutual exclusion algorithm for open distributed computing systems that can evolve their behavior based on membership changes in the environment. The algorithm consists of two main layers; the quorum-consensus and quorum-reconfiguration. The quorum consensus layer is used to handle requests from and to the application layer, and it directly adopts a proposed k-coterie based algorithm of the group k-mutual exclusion in the static environments without any change to its protocol. Thus, the message complexity and quorum availability are the same as in the static environments. The quorum reconfiguration reconstructs information structure of the k-coterie by simply implementing the properties of two quorum input operations called coterie-join and coterie-cross. The reconfiguration layer is simple to use and has a great ability to complete any operation during reconfiguration powerfully thus system does not enter the halt state.

Stochastic field model for autonomous robot learning

Through reinforcement learning, an autonomous robot creates an optimal policy which maps state space to action space. The mapping is obtained by trial and error through the interaction with a given environment. The mapping is represented as an action-value function. The environment accords an information in the form of scalar feedback known as a reinforcement signal. As a result of reinforcement learning, an action has the high action-value in each state. The optimal policy is equivalent to choosing an action which has the highest action-value in each state. Typically, even if an autonomous robot has continuous sensor values, the summation of discrete values is used as an action-value function to reduce learning time. However, the reinforcement learning algorithms including Q-learning suffer from errors due to state space sampling. To overcome the above, we propose an EQ-learning (extended Q-learning) based on a SFM (stochastic field model). EQ-learning is designed in order to accommodate continuous state space directly and to improve its generalization capability. Through EQ-learning, an action-value function is represented by the summation of weighted base functions, and an autonomous robot adjusts weights of base functions at learning stage. Other parameters (center coordinates, variance and so on) are adjusted at the unification stage where two similar functions are unified to a simpler function.

Filtering and segmentation of digitized land use map images

Abstract. One important step in the analysis of digitized land use map images is the separation of the information in layers. In this paper we present a technique called Selective Attention Filter which is able to extract or enhance some features of the image that correspond to conceptual layers in the map by extracting information from results of clustering of local regions on the map. Different parameters can be used to extract or enhance different information on the image. Details on the algorithm, examples of application of the filter and results are also presented.

MPSS ­ Multi Process System Simulator

MPSS simulates the behavior of a high traffic transaction processing system. An effective use of MPSS is the analysis of the impact of exclusive control of system resources over multiple processes. MPSS consists of a control process and multiple application processes. The control process is designed to simulate a transaction processing monitor. It initiates and oversees multiple application processes running concurrently. An application process behaves as a transaction processing application, however it does not access databases, or communicate with remote users. Instead, it consumes CPU, holds system resources, and waits for an event or a resource by invoking system calls provided by the MPSS system call library. Some of the system calls provided are LOCK and UNLOCK, both for controlling exclusive use of a resource, and WAIT, for an event of a resource to be released by other processes or for a defined time period to simulate process wait for events such as I/O completions. All the activities are traced and logged for later analysis. MPSS can also be used as a test bed for a system call library routine in testing and/or evaluating its effect to the system. It is also possible to test a new application model in the MPSS environment in regard to its affect to existing system activities before going into production.

Clear separation and combination of synchronization constraint for concurrent object oriented programming

This paper presents a language framework for a concurrent description and an implementation of a synchronization mechanism in distributed object-oriented computation. Some concurrent object-oriented languages are considered to be constructed from a user-defined function and a synchronization constraint. We propose the language for the synchronization constraint, which allows to define mutual exclusion and conditional synchronization by using declarative notations. The synchronization constraint is separated from user-defined functions, and the relation between them is described in the binding code. The binding mechanism reduces the dependency between them and contributes to code reuse. This framework makes it is easy for programmers to understand and describe the use-defined functions and synchronization constraints independently. The implementation of the synchronization mechanism is based on a reconfigurable object model that we are developing. The user-defined function and synchronization mechanism are implemented as its own separated module in the single object. Then the synchronization mechanism has flexibility and preserves the concept of object-orientation.