Euan W. Dempster

Dynamic Information Presentation through Web-based Personalisation and Adaptation — An Initial Review

Personalisation and adaptation of information and information presentation to reflect user needs and interests is an area in which there is considerable interest. DIP, Dynamic Information Presentation, is a research project that focuses on problems in this area. As part of this research a review has been conducted of existing Web-based information applications from a variety of domains that use such techniques, and a set of dimensions proposed as a basis for analysing andcomparing them. The applications fall naturally into three categories. The results provide a useful step towards a general framework for classifying these approaches.

Approximate Estimation of Transaction Response Time

This paper describes a study of different approximation techniques used to predict the response times of database transactions represented as patterns of resource consumption and modelled with non-product-form queueing networks. The techniques are applied to a range of examples. The experiments show that none of the approximation techniques has a consistent advantage over the others for all cases considered. On the other hand, a simple heuristic rule is formulated which provides an acceptable approximation to the average transaction response time for the entire range of examples. The rule specifies a procedure for labelling each queue in a queueing network as either an M/M/1 or an M/G/1 resource. The resulting network can then be solved to obtain the mean response time of individual transactions.

An analytical tool for predicting the performance of parallel relational databases

The uptake of parallel DBMSs is being hampered by uncertainty about the impact on performance of porting database applications from sequential to parallel systems. The development of tools which aid the system manager or machine vendor could help to reduce this problem. This paper describes an analytical tool which determines the performance characteristics (in terms of throughput, resource utilisation and response time) of relational database transactions executing on particular machine configurations and provides simple graphical visualisations of these to enable users to obtain rapid insight into particular scenarios. The problems of handling different parallel DBMSs are illustrated with reference to three systems – Ingres, Informix and Oracle. A brief description is also given of two different approaches used to confirm the validity of the analytical approach on which the tool is based. Copyright

Verifying a Performance Estimator for Parallel DBMSs

Although database systems are a natural application for parallel machines, their uptake has been slower than anticipated. This problem can be alleviated to some extent by the development of tools to predict the performance of parallel database systems and provide the user with simple graphic visualisations of particular scenarios. However, in view of the complexities of these systems, verification of such tools can be very difficult. This paper describes how both process algebra and simulation are being used to verify the STEADY parallel DBMS performance estimator.

A toolkit for creating personalized presentations

With the explosion in the availability of information online, users are finding it increasingly difficult to track down the specific material that they require. Users are therefore becoming increasingly dependent on intelligent services to provide information that is dynamically selected and presented according to their preferences. However, development of these personalized services is not trivial. Significant effort is required in terms of engineering the underlying knowledge that is used by a service to determine which information might be relevant to a particular user and how to present it. A Toolkit that reduces the complexity involved in the creation and maintenance of such services is discussed.

A tool for supporting the teaching of parallel database systems

Parallel database systems are complex entities. When teaching about these systems as part of a course in a limited time, one has difficulty providing useful practical experience that gives a deep insight into system behavior and operation. This paper describes a tool for performance prediction that has been developed to aid the visualization of parallel database systems and that is currently being used to support teaching. The tool enables students to experiment with different hardware and software configurations and to view the effects of changes on the performance of the system. The tool provides insight into how data can be placed among the nodes of a parallel machine according to predefined strategies, as well as manually, and provides feedback on the effect of these on throughput and response time. This tool is able to provide a good appreciation of the concepts in a relatively short period of time.

Modelling Parallel Oracle for Performance Prediction

The problem of predicting the performance of a parallel relational DBMS for a set of queries applied to a particular data set on a shared nothing parallel architecture without transferring the application to a parallel system is a challenging one. An analytical approach has been developed to assist with this task and has been applied to the ICL GoldRush machine, a parallel machine with a shared-nothing architecture. This paper describes how the Oracle Parallel Server and the Parallel Query Option are modelled by the method and compares the predictions of the model against actual measurements obtained.

Some Results from a New Technique for Response Time Estimation in Parallel DBMS

The need for tools for performance prediction of parallel database systems is generally recognised. One such tool which has been developed (Steady) is based on analytical techniques to obtain a rapid estimate of performance. The approach to predicting response time involves a heuristic approximation coupled with standard queueing solutions. This paper reports on preliminary results for both maximum transaction throughput and response time obtained in comparing this approach against actual measurements.

STEADY - A Tool for Predicting Performance of Parallel DBMSs

Predicting the performance of a parallel relational DBMS executing an arbitrary set of transactions on particular data sets for different architectural configurations with different data placement strategies is a non-trivial task. An analytical tool has been developed to assist with this task and can be used for application sizing, capacity planning and performance tuning.

Constraining XML transformations for personalised information presentation

Through the use of different stylesheets it is possible to transform the information contained in XML documents and present it in different ways, for example to create personalised presentations. However, in doing so there is a danger that the transformation may result in a presentation, which fails to carry the essential message intended by the provider of the source document. We believe that the Information Provider should be able to provide constraints on permitted transformations of their document, stating for example which elements are mandatory, which must not be changed, which must have the order preserved. This paper discusses the need for such transformation constraints, and proposes a simple metadata annotation expressing the required constraints. We consider the adequacy of the proposed approach, and alternative ways to constrain transformations.