/ Sabhash Bhalla / Associate Professor
Technological advances in the area of data modeling and design of information systems, aim to capture a wide variety of applications into the fold of database systems technology. In the near future, Database Systems are likely to be in use within a diverse range of applications concerning banking, insurance, spacecraft monitoring, and many other applications such as monitoring industrial power grids.
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 models. One such example is that of Object-Oriented data modelling techniques for representation of complex data objects.
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. This situation has led to concentrated efforts by many researchers to find suitable transaction management strategies and alternatives.
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. A brief outline of the ongoing projects is given below.
Data Modelling for Complex Objects
Information Processing Systems of the 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 ``Data Modelling for Complex Objects", new approaches for representing such objects are being explored.
One of the new challenging areas 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 unsuitable for adoption in new application environments. Many new approaches that are more appropriate for the new environment are being studied.
Refereed Journal Papers
Replicated data management systems adopt the 1-copy serializability criteria for processing transactions. In order to achieve this goal, many approaches rely on obtaining votes from other sites for processing update requests. In the proposed approach, a technique for generation of precedence graphs for each transaction execution is analyzed. The transaction data flow graph approach is a fully distributed approach. The proposed technique is free from deadlocks, and avoids resubmission of transactions.
Refereed Proceeding Papers
In the existing voting based approaches, the update request is executed, and the variables are sent to other sites for majority approval. In these approaches, if the submitted transactions are in serializability conflict, then some of the transactions are rejected. These transactions are resubmitted for execution, and by this, these incur additional processing delays and overheads. A technique has been proposed, that generates a partial data flow graph on visits to sites by a transaction.
In a temporal DBMS environment the data and the schema definition evolves with time. An effective method to implement an evolving schema is by supporting versions of schema within the DBMS. A hierarchical schema definition which can implement versions of schema has been studied. A hierarchical schema definition that supports the property of dynamic evolution has been incorporated. The query languages can support queries on data model using this approach.
Doctoral Dissertations Advised
Thesis Advisor: Subhash Bhalla.
Thesis Advisor: Subhash Bhalla.