RAFDA: A Policy-Aware Middleware Supporting the Flexible Separation of Application Logic from Distribution

Middleware technologies often limit the way in which object classes may be used in distributed applications due to the fixed distribution policies that they impose. These policies permeate applications developed using existing middleware systems and force an unnatural encoding of application level semantics. For example, the application programmer has no direct control over inter-address-space parameter passing semantics. Semantics are fixed by the distribution topology of the application, which is dictated early in the design cycle. This creates applications that are brittle with respect to changes in distribution. This paper explores technology that provides control over the extent to which inter-address-space communication is exposed to programmers, in order to aid the creation, maintenance and evolution of distributed applications. The described system permits arbitrary objects in an application to be dynamically exposed for remote access, allowing applications to be written without concern for distribution. Programmers can conceal or expose the distributed nature of applications as required, permitting object placement and distribution boundaries to be decided late in the design cycle and even dynamically. Inter-address-space parameter passing semantics may also be decided independently of object implementation and at varying times in the design cycle, again possibly as late as run-time. Furthermore, transmission policy may be defined on a per-class, per-method or per-parameter basis, maximizing plasticity. This flexibility is of utility in the development of new distributed applications, and the creation of management and monitoring infrastructures for existing applications.Comment: Submitted to EuroSys 200

A Comparative Evaluation of .net Remoting and JAVA RMI

Distributed application technologies such as Micrososoft.NET Remoting, and Java Remote Method Invocation (RMI) have evolved over many years to keep up with the constantly increasing requirements of the enterprise. In the broadest sense, a distributed application is one in which the application processing is divided among two or more machines. Distributed middleware technologies have made significant progress over the last decade. Although Remoting and RMI are the two of most popular contemporary middleware technologies, little literature exists that compares them. In this paper, we study the issues involved in designing a distributed system using Java RMI and Microsoft.NET Remoting. In order to perform the comparisons, we designed a distributed distance learning application in both technologies. In this paper, we show both similarities and differences between these two competing technologies. Remoting and RMI both have similar serialization process and let objects serialization to be customized according to the needs. They both provide support to be able to connect to interface definition language such as Common Object Request Broker Architecture (CORBA). They both contain distributed garbage collection support. Our research shows that programs coded using Remoting execute faster than programs coded using RMI. They both have strong support for security although implemented in different ways. In addition, RMI also has additional security mechanisms provided via security policy files. RMI requires a naming service to be able to locate the server address and connection port. This is a big advantage since the clients do not need to know the server location or port number, RMI registry locates it automatically. On the other hand, Remoting does not require a naming service; it requires that the port to connect must be pre-specified and all services must be well-known. RMI applications can be run on any operating system whereas Remoting targets Windows as the primary platform. We found it was easier to design the distance learning application in Remoting than in RMI. Remoting also provides greater flexibility in regard to configuration by providing support for external configuration files. In conclusion, we recommend that before deciding which application to choose careful considerations should be given to the type of application, platform, and resources available to program the application

Using a Commercial Framework to Implement and Enhance the IEEE 1451.1 Standard

In 1999, the 1451.1 Std was published defining a common object model and interface specification to develop open, multi-vendor distributed measurement and control systems. However, despite the well-known advantages of the model, few have been the initiatives to implement it. In this paper we describe the implementation of a NCAP – Network Capable Application Processor, in a well-known and well-proven infrastructure: the Microsoft .NET Framework. The choice of a commercial framework was part of our strategy: to take advantage of several “of the shelf” technologies and adapt them to produce a NCAP prototype, called NCAP/XML. In addition, a solution to enhance the 1451.1 Std is presented by proposing a new format for inter-NCAP communication based on XML (eXtended Markup Language)

Building a Truly Distributed Constraint Solver with JADE

Real life problems such as scheduling meeting between people at different locations can be modelled as distributed Constraint Satisfaction Problems (CSPs). Suitable and satisfactory solutions can then be found using constraint satisfaction algorithms which can be exhaustive (backtracking) or otherwise (local search). However, most research in this area tested their algorithms by simulation on a single PC with a single program entry point. The main contribution of our work is the design and implementation of a truly distributed constraint solver based on a local search algorithm using Java Agent DEvelopment framework (JADE) to enable communication between agents on different machines. Particularly, we discuss design and implementation issues related to truly distributed constraint solver which might not be critical when simulated on a single machine. Evaluation results indicate that our truly distributed constraint solver works well within the observed limitations when tested with various distributed CSPs. Our application can also incorporate any constraint solving algorithm with little modifications.Comment: 7 page

Pembuatan System Corporate Messenger Pada Jaringan Lan

Corporate messenger is the one of the application that can be used for communication in a local area network. The backgrounds of this topic are needs of sending message process in the LAN. The messages which want to be presented are not only in a text format, but also can be in audio visual format. Computer client will connect to the server. When the connection has been established, the client continued the authentication and started sending message between client and server. Audio and video message sending can be done with peer to peer connection with entering the IP address first from remote user that we want to communicate with. The evaluation of this application was done by using 3 computers and as the result, we found that authentication process can work properly, sending text message was done properly and communication using audio can be heard clearly. In addition to video sending message, we could see directly in remote client. The average time to show the video on remote client is 3.771 seconds

Towards Adaptable and Adaptive Policy-Free Middleware

We believe that to fully support adaptive distributed applications, middleware must itself be adaptable, adaptive and policy-free. In this paper we present a new language-independent adaptable and adaptive policy framework suitable for integration in a wide variety of middleware systems. This framework facilitates the construction of adaptive distributed applications. The framework addresses adaptability through its ability to represent a wide range of specific middleware policies. Adaptiveness is supported by a rich contextual model, through which an application programmer may control precisely how policies should be selected for any particular interaction with the middleware. A contextual pattern mechanism facilitates the succinct expression of both coarse- and fine-grain policy contexts. Policies may be specified and altered dynamically, and may themselves take account of dynamic conditions. The framework contains no hard-wired policies; instead, all policies can be configured.Comment: Submitted to Dependable and Adaptive Distributed Systems Track, ACM SAC 200

Keyword Indexing and Searching for Large Forensics Targets using Distributed Computing

When computer forensics investigation is carried out on single workstations and the forensics image in hand is of terabytes of length, indexing of keywords takes a heavy toll. With the manifold increase of forensics data, there is an urgent need to develop a distributed digital forensics toolkit associated with sophisticated indexing and searching capabilities which utilizes multiple idle computers to index forensics images. This toolkit will deliver fast paced search performance running indexing of large forensics data and will produce smaller indexing time and faster search speeds as compared to non indexed searches on standalone workstations. The distributed resources of available computers thus make an ideal platform for virtual supercomputing performing indexing and searching on available machines

Creating a Distributed Programming System Using the DSS: A Case Study of OzDSS

This technical report describes the integration of the Distribution Subsystem (DSS) to the programming system Mozart. The result, OzDSS, is described in detail. Essential when coupling a programming system to the DSS is how the internal model of threads and language entities are mapped to the abstract entities of the DSS. The model of threads and language entities of Mozart is described at a detailed level to explain the design choices made when developing the code that couples the DSS to Mozart. To show the challenges associated with different thread implementations, the C++DSS system is introduced. C++DSS is a C++ library which uses the DSS to implement different types of distributed language entities in the form of C++ classes. Mozart emulates threads, thus there is no risk of multiple threads accessing the DSS simultaneously. C++DSS, on the other hand, makes use of POSIX threads, thus simultaneous access to the DSS from multiple POSIX threads can happen. The fundamental differences in how threads are treated in a system that emulates threads (Mozart) to a system that make use of native-threads~(C++DSS) is discussed. The paper is concluded by a performance comparison between the OzDSS system and other distributed programming systems. We see that the OzDSS system outperforms ``industry grade'' Java-RMI and Java-CORBA implementations