/ Subhash Bhalla / Associate Professor
Current developments in the area of data modeling and information systems' design aim to capture a wide variety of applications into the fold of DBMS (Database Management System) technology. This is due to improved understanding of information extracted from databases by the usage of advanced DBMS techniques. The DBMSs currently use visual representations within new interfaces to manage large volumes of data, and also to manage data that may have complex features associated with its structure. In addition to complexity in features, such as multiple attributed data, wave-forms and multi-dimensional orientation, many new types of raw data are emerging that need to be captured by DBMSs for the purpose of information extraction. Among these, the image data and video image data are two important forms of data and many research efforts are being made to make suitable DBMS architectures for image and video databases.
In order to provide flexibility in terms of data representation, the databases need the support of powerful data-modelling techniques. Most of the advances in techniques concentrate on capturing more meaning within data that is made resident on a computer system. Within this framework, a number of researchers are actively developing improved data management strategies. The database systems laboratory aims to participate in research activity to promote Database utilization for new applications.
The laboratory has activity in progress in the area of transaction processing and modelling of data objects for new applications. In case of new applications, different applications have varying needs in terms of data representation and operations that need to be performed. Many applications add many types of transactions and many types of processing constraints.
The transaction processing environments occuring in various applications include, real-time systems, distributed database systems, main-memory resident systems, distributed heterogeneous database systems, and applications requiring complex data representations based on Object-Oriented databases. The transaction management issues among various application environments consider successful completion of user transactions. There are a number of transaction processing domains being explored by researchers in this line of activity. These include - long duration transactions, nested transactions, time-critical transactions, distributed computing, committing transactions in the event of failures, and management of replicated databases.
There is a continuing evolution of computer systems as a hierarchy of computing elements that cooperate to perform computations. In addition complex software systems also introduce multiple layers of software. Thus, the activity of performance evaluation of transaction processing systems is an important area that provides improved understanding of systems. This facilitates improved integration and refinement in technique.
The Database Systems Laboratory has research activity concentrating on data modelling as well as transaction processing activity. A brief outline of the ongoing projects is given below.
Information Processing Systems of future will be a combination of integrated components. There will be components for intelligent problem solving, or decision making, components for specialized data processing (e.g., image enhancers), and components for shared information management. The applications will utilize a shared base of information. The examples of some of the application domains are business automation, industrial automation, computer-aided design and manufacture, and cartography. Under the "Data Modelling for Complex Objects" the new approaches for representing such objects are being explored. Among these relation of graphics and databases is being studied.
One of the new challenging area of interest in transaction management is that of Real-time database systems in which transactions have time constraint. Within the new environment, the database management system must support a mix of ordinary as well as real-time transactions. The transaction support must also be highly reliable and fast.
Traditional approaches to transaction management introduce elements of unpredictable delays during transaction processing. Thus, making these not suitable for adoption in new application environments. Many new approaches that are more appropriate for the new environment are being studied.
Refereed Journal Papers
Transaction management consists of many components, such as scheduling, concurrency control, recovery, and distributed commit. These components are designed independently and introduce varying levels of delays. For example, Concurrency control based on distributed locking, requires additional efforts for deadlock detection and elimination. The possibility of a deadlock leads unpredictable delays, and repeated restarts of transactions in distributed systems. On the contrary, real-time transactions require a response within a time limit. In this study, an effort has been made for countering the delay problems.
Japanese is often characterized as a difficult foreign language for a Westerner to learn. While differences in vocabulary, grammar, and culture contribute to this difficulty, the main problem is the complex writing system which, utilizing many thousands of characters. Very often, the student of Japanese simply cannot read. In addition to the usual bilingual dictionaries, the student must use dictionaries not only for the ordinary uses of characters, but also for unique and idiosyncratic uses of characters in personal and place names. Modern storage media such as CD-ROMs and magnetic-optical disks permit large amounts of data to be stored so that the information contained in a set of bilingual and character dictionaries can be compactly represented. The information thus represented can be treated as a linguistic database which can be deductively accessed, combining many linear dictionaries into a single multi-linear dictionary.
A number of dictionaries are needed in order to locate a reference in Japanese language. The methods of refering to information in these dictionaries are very time consuming. Also, most of the options that are available are more convenient for native users of Japanese language. To surmount this difficulty, the exiting methods for indexing information in Japanese dictionaries are studied in this paper.
Consistent recovery from process failures is an essential component of reliable distributed systems. Many existing recovery techniques use asynchronous message logging and checkpoints. Most of the present approaches depend on logged states of non-fail processes for recovery. A model of recovery based on the current active states of processes has been proposed. The algorithm considers recoverable state of the failed process and current states of the non-failed processes. Each process recovers to a consistent system state independently.