Master Thesis - Past Projects - Abstract

QoS Management in Configurable Real-Time Databases

ID: LiTH-IDA-EX 04/071-SE

In response to the increasing demand for embedded systems with real-time database support,a configurable real-time database (COMET) has been developed. To get the advantages of both component-based software development and aspect-oriented software development, COMET was designed following a novel method for aspectual component-based real-time system development (ACCORD). A class of embedded real-time systems can accept that a subset of their data-manipulation tasks fail to complete before their deadlines. These soft real-time systems require guarantees that the number of missed deadlines stay below a specified percentage at all times. The aim of this project is to extend the COMET library with components and aspects to implement two algorithms that provide guarantees for missed deadlines. The first algorithm is a Feedback Control algorithm based on deadline Miss ratio (FC-M). It uses the deadline miss ratio to adjust an admission controller. The second algorithm is a QoS-sensitive approach for tiMeliness and Freshness guarantees (QMF) and extends FC-M to handle of the freshness of data. It uses information about how often various data items are requested,to reject unnecessary updates of these data items. FC-M and QMF have been implemented as components and aspects to allow tailoring of COMET to meet the demands of more applications. Subsets of the new components and aspects can also be used with other configurations to provide various functionality, and, thus, improving the reconfiguratbility of COMET. When woven into COMET, FC-M significantly improves the deadline miss ratio under overloads. QMF, on the other hand, proved less useful.

Keywords: aspect-oriented sofware development, component-based software development, real-time databases, feedback control scheduling, quality of service, freshness guarantees

Author(s): Mikael Björk

Contact: Jörgen Hansson