Deleting completed transactions

AbstractWe derive necessary and sufficient conditions on when it is safe to forget (and remove) a completed transaction in several versions of conflict-graph-based schedulers. We show that the conditions can be applied repeatedly and analyze their complexity

Developing A System To Evaluate Text\u27s Suitability For Use In Greek Language Teaching

Internet is a dynamic corpus, a huge digital library of authentic material which is of particular im- portance to language teaching. In the modern pedagogical framework, language teaching is based on the genre-based approach and on the teaching of language to its authentic use. Viewing the Web as a corpus for the purposes of language teaching and due to the difficulty on selecting suitable texts with specific grammatical information from the Web, this paper presents the development life cycle phases of the system diaKeimenou. The literature review showed the research gap in relation to the ways of searching and finding a suitable text for use in the language teaching according to specific linguistic characteristics associated with the teaching objectives. The computational tool by the name diaKeimenou which is presented in this paper aims to fill this gap and help the teacher to evaluate text’s suitability given the specified learning objectives without much effort and time. The results from the usability evaluation show that the tool diaKeimenou is useful and easy to use

A DISTRIBUTED E-LEARNING SERVICE FOR REMOTE AREAS

The cloud-compatible architecture of a distributed distance e-learning system which has been deployed and is being utilized in five remote areas in Eastern Europe (Finland, Poland, Bulgaria, Greece and Cyprus) is presented and discussed as a case study of e-learning. A series of e-courses is being conducted with a variety of learning tools and techniques: a Virtual World, Web 2.0 tools, a web conference platform and a learning management system. Emphasis is placed on the feasibility of the delivery of the integrated Distance Learning (DL) service through distributed web services; an architecture is proposed that extends the existing one by implementing the DL service in the form of a SOA in a hybrid cloud

On the Creation of Sustainable Design Patterns of ICT Integration in the Classroom

The paper focuses on the methodology of making observations that account for the actual use of ICT infrastructure and tools in the classroom. The observational study is part of a project that focuses on scenario feasibility as an enabler of ICT usage. In particular, the observations provide input on pattern mining with the aim to help teachers and other stakeholders in the decision-making process of selecting suitable ICT facilities

Orchestration Graphs: Enabling Rich Social Pedagogical Scenarios in MOOCs

One of the initial promises of MOOCs was to enable participants from around the world to learn and build knowledge together, however existing MOOC platforms are very limited in their collaborative functionality. Using a recent educational modeling language which can express a broad diversity of educational scenarios, we present a technical infrastructure design and prototype which enables instructors to design and run pedagogically rich and therefore complex scenarios. We present this as a theoretical and technical contribution to support a broad program of research and innovation related to collaborative learning at scale

FROG: rapid prototyping of collaborative learning scenarios

We describe FROG, an integrated environment for authoring and running collaborative learning scenarios, called Orchestration Graphs. We describe the pedagogical background and the technical architecture, and present a case study of a teacher using FROG to experiment with a variation of a jigsaw script

Transaction Synchronisation In Object Bases

We propose a formal model of concurrency control in object bases. An object base is like a database except that information is represented in terms of "objects" that encapsulate both data and the procedures through which the data can be manipulated. The model generalises the classical model of database concurrency control: it allows for nested transactions (as opposed to flat transactions) which may issue arbitrary operations (as opposed to just read and write operations). We establish an analogue to the classical serialisability theorem and use it to derive simple proofs of correctness of two concurrency control algorithms for object bases, namely Nested Two-Phase Locking (Moss' algorithm) and Nested Timestamp Ordering (Reed's algorithm). Concurrency control in object bases can be viewed as a combination of intra-object and inter-object synchronisation. The former ensures that each object's own methods are executed in serialisable fashion; the latter ensures the compatibility of trans..