Distributed databases and other networked information systems use copies or mirrors to reduce latency and to increase availability. Copies need to be refreshed. In a loosely coupled system, the copy sites are typically responsible for synchronizing their own copies. This involves polling and can be quite expensive if not done in a disciplined way. We explore the topic of how to determine a refresh schedule given knowledge of the update frequencies and limited bandwidth. The emphasis here is on how to use additional information about the aggregate interest of the user community in each of the copies in order to maximize the perceived freshness of the copies. We develop a model and an optimal solution for small cases, presents several heuristic algorithms that work for large cases, then explores the impact of object size on the refresh schedule. It also presents experimental evidence that our algorithms perform quite well.

We describe an index hint mechanism for on-demand data broadcast environments, which enables mobile clients to spend less power consumption by reducing their tuning times. We propose approaches to estimate the data broadcast times for a set of data items so that the index mechanism can be applied to on-demand data broadcasts. We also propose how to organize and apply index hints using the estimated broadcast times of data items. Our simulation results show that the proposed index hint mechanism effectively reduces the tuning times of mobile clients, thereby reducing their power consumption.

The productivity of software development largely depends on the degree of how much the ready-made software components are reused effectively. An object-oriented application framework is a semi-completed application. It enables software developers to reuse the knowledge from the application analysis and design phase as well as the development phase of software. As object-oriented frameworks are complex and large, the effectiveness of conventional approaches to retrieve reusable frameworks may be reduced. This paper proposes to model object-oriented frameworks using XML (Extensible Markup Language) and apply a retrieval technique for structured documents. It characterizes elements for describing framework information and suggests their schema. It also increases the effectiveness of search by expanding similar terms through query reformulation.

Previous works on buffer management in the database area paid little attention to the dynamic buffer allocation involving reallocation of buffers of queries while exploiting the known access patterns of the database operations. This paper proposes a new buffer allocation technique to improve the system's global performance. The main idea is to maximize the effectiveness of the buffer allocation. For this end, the less-utilized buffers of queries are partially preempted and reallocated to the other queries which can utilize them more effectively. The proposed technique reduces the waiting time portion of query processing through the flexible buffer allocation. The simulation results show that the proposed technique performs better than the conventional ones.