XML (Extensible Markup Language) is a language used in data representation and storage, and transmission and manipulation of data. Excessive memory consumption is an important challenge when representing XML documents in main memory. Document Object Model (DOM) APIs are used in a processing level that provides access to all parts of XML documents through the navigation operations. Although DOM serves as a a general purpose tool that can be used in different applications, it has high memory cost particularly if using naïve. The space usage of DOM has been reduced significantly while keeping fast processing speeds, by use of succinct data structures in SiXDOM [1]. However, SiXDOM does not explore in depth XML data compression principles to improve in-memory space usage. Such XML data compression techniques have been proven to be very effective in on-disk compression of XML document. In this thesis we propose a new approach to represent XML documents in-memory using XML data compression ideas to further reduce space usage while rapidly supporting operations of the kind supported by DOM. Our approach is based upon a compression method [2] which represents an XML document as a directed acyclic graph (DAG) by sharing common subtrees. However, this approach does not permit the representation of attributes and textual data, and furthermore, a naive implementation of this idea gives very poor space usage relative to other space-efficient DOM implementations [1]. In order to realise the potential of this compression method as an in-memory representation, a number of optimisations are made by application of succinct data structures and variablelength encoding. Furthermore, a framework for supporting attribute and textual data nodes is introduced. Finally, we propose a novel approach to representing the textual data using Minimal Perfect Hashing(MPH). We have implemented our ideas in a software library called DAGDOMand performed extensive experimental evaluation on a number of standard XML files. DAGDOM yields a good result and we are able to obtain significant space reductions over existing space-efficient DOM implementations (typically 2 to 5 times space reduction), with very modest degradations in CPU time for navigational operations.

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Service technology geared by its SOA architecture and enabling Web services is rapidly gaining in maturity and acceptance. Consequently, most worldwide (private and corporate) cross-organizations are embracing this paradigm by publishing, requesting and composing their businesses and applications in the form of (web-)services. Nevertheless, to face harsh competitiveness such service oriented cross-organizational applications are increasingly pressed to be highly composite, adaptive, knowledge-intensive and very reliable. In contrast to that, Web service standards such as WSDL, WSBPEL, WS-CDL and many others offer just static, manual, purely process-centric and ad-hoc techniques to deploy such services. The main objective of this thesis consists therefore in leveraging the development of service-driven applications towards more reliability, dynamically and adaptable knowledge-intensiveness. This thesis puts forward an innovative framework based on distributed high-level Petri nets and event-driven business rules. More precisely, we developed a new variant of high-level Petri Nets formalism called Service-based Petri nets (CSrv-Nets), that exhibits the following potential characteristics. Firstly, the framework is supported by a stepwise methodology that starts with diagrammatical UML-class diagrams and business rules and leads to dynamically adaptive services specifications. Secondly, the framework soundly integrates behavioural event-driven business rules and stateful services both at the type and instance level and with an inherent distribution. Thirdly, the framework intrinsically permits validation through guided graphical animation. Fourthly, the framework explicitly separates between orchestrations for modelling rule-intensive single services and choreography for cooperating several services through their governing interactive business rules. Fifthly, the framework is based on a two-level conceptualization: (1) the modelling of any rule-centric service with CSrv-Nets; (2) the smooth upgrading of this service modelling with an adaptability-level that allows for dynamically shifting up and down any rule-centric behavior of the running business activities.

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