Client/server computing

Autonomous Underwater Vehicles (AUV) collect a large volume of scientific data in every mission, using the onboard sensors, and store them in log files. The accessibility of these data is limited. Specific tools are required to extract the data to be processed on the user workstation with the installed analysis tools and scripts. The objective is to standardize and simplify the way data can be retrieved and processed from anywhere by anybody. The design of a server that manages the access to the data and to the applications that process them has been considered. Everything can then be done through the use of a single Java client executed on any Java compliant computer. Analysis tools are downloaded on the fly when needed and do not require any installation. New tools can be integrated into the application server in the form of plugins developed with an appropriate Java Library.

In this dissertation, an object-based I/O architecture for personal computers (PCs) and workstations is proposed. The proposed architecture allows the flexibility of having I/O processing performed as much as possible by intelligent I/O adapters, or by the host processor, or by any processor in the system, depending on application requirements and underlying hardware capabilities. It keeps many good features of current I/O architectures, while providing more flexibility to take advantage of new hardware technologies, promote architectural openness, provide better performance and higher reliability. The proposed architecture introduces a new definition of I/O subsystems and makes use of concurrent object-oriented technology. It combines the notions of object and thread into something called an active object. All concurrency abstractions required by the proposed architecture are provided through external libraries on top of existing sequential object-oriented languages, without any changes to the syntax and semantics of these languages. We also evaluate the performance of optimal implementations of the proposed I/O architecture against other I/O architectures in three popular, PC-based, distributed environments: network file server, video server, and video conferencing. Using the RESearch Queueing Modeling Environment (RESQME), we have developed detailed simulation models for various implementations of the proposed I/O architecture and two other existing I/O architectures: a conventional, interrupt-based I/O architecture and a peer-to-peer I/O architecture. Our simulation results indicate that, on several different hardware platforms, the proposed I/O architecture outperforms both existing architectures in all three distributed environments considered.

The Java Devlopment Environment defines SQLJ as a standard way of embedding the relational database language SQL in the object-oriented programming language Java. Oracle Corporation provides an extension of SQLJ that supports dynamic SQL constructs for the processing of SQL commands that are not completely known at compile time. Unfortunately, these constructs are not sufficient to handle all dynamic situations, so that the programmer has to depend on other SQL embeddings, such as JDBC, in addition to Oracle's SQLJ. In this thesis we implement several extensions to Oracle's SQLJ so that all dynamic situations can be programmed in SQLJ, without resorting to other SQL embeddings. We also add a sub-query based for loop facility, similar to the one provided in Oracle's database programming language PL/SQL, as an improvement over the iterator constructs that SQLJ provides. This thesis discusses the design, development and implementation of these SQLJ extensions, and provided applications that show the utility of these extensions in terms of clarity and power.