Core Technologies for Native XML Database Management Systems

This work investigates the core technologies required to build Database Management Systems (DBMSs) for large collections of XML documents. We call such systems XML Base Management Systems (XBMSs). We identify requirements, and analyze how they can be met using a conventional DBMS. Our conclusion is that an XML support layer on top of an existing conventional DBMS does not address the requirements for XBMSs. Hence, we built a Native XBMS, called Natix. Natix has been developed completely from scratch, incorporating optimizations for high-performance XML processing in those places where they are most effective

The Replica Consistency Problem in Data Grids

Fast and reliable data access is a crucial aspect in distributed computing and is often achieved using data replication techniques. In Grid architectures, data are replicated in many nodes of the Grid, and users usually access the "best" replica in terms of availability and network latency. When replicas are modifiable, a change made to one replica will break the consistency with the other replicas that, at that point, become stale. Replica synchronisation protocols exist and are applied in several distributed architectures, for example in distributed databases. Grid middleware solutions provide well established support for replicating data. Nevertheless, replicas are still considered read-only, and no support is provided to the user for updating a replica while maintaining the consistency with the other replicas. In this thesis, done in collaboration with the Italian National Institute of Nuclear Physics (INFN) and the European Organisation for Nuclear Research (CERN), we study the replica consistency problem in Grid computing and propose a service, called CONStanza, that is able to synchronise both files and heterogeneous (different vendors) databases in a Grid environment. We analyse and implement a specific use case that arises in high energy Physics, where conditions databases are replicated using databases of different makes. We provide detailed performance results, and show how CONStanza can be used together with Oracle Streams to provide multitier replication of conditions databases using Oracle and MySQL databases

Semantic discovery and reuse of business process patterns

Patterns currently play an important role in modern information systems (IS) development and their use has mainly been restricted to the design and implementation phases of the development lifecycle. Given the increasing significance of business modelling in IS development, patterns have the potential of providing a viable solution for promoting reusability of recurrent generalized models in the very early stages of development. As a statement of research-in-progress this paper focuses on business process patterns and proposes an initial methodological framework for the discovery and reuse of business process patterns within the IS development lifecycle. The framework borrows ideas from the domain engineering literature and proposes the use of semantics to drive both the discovery of patterns as well as their reuse