Recovery within long running transactions

As computer systems continue to grow in complexity, the possibilities of failure increase. At the same time, the increase in computer system pervasiveness in day-to-day activities brought along increased expectations on their reliability. This has led to the need for effective and automatic error recovery techniques to resolve failures. Transactions enable the handling of failure propagation over concurrent systems due to dependencies, restoring the system to the point before the failure occurred. However, in various settings, especially when interacting with the real world, reversal is not possible. The notion of compensations has been long advocated as a way of addressing this issue, through the specification of activities which can be executed to undo partial transactions. Still, there is no accepted standard theory; the literature offers a plethora of distinct formalisms and approaches. In this survey, we review the compensations from a theoretical point of view by: (i) giving a historic account of the evolution of compensating transactions; (ii) delineating and describing a number of design options involved; (iii) presenting a number of formalisms found in the literature, exposing similarities and differences; (iv) comparing formal notions of compensation correctness; (v) giving insights regarding the application of compensations in practice; and (vi) discussing current and future research trends in the area.peer-reviewe

ABC Analysis in an Internet Shop: A New Set of Criteria

This article presents a model of ABC analysis tailored for internet shops. The standard set of criteria is expanded to cover e-commerce specific characteristics, such as the number of product views, search engine rankings and product links via a recommendation system..The proposed new methodology is applied to real data from an internet bookstore in Poland. A comparison with the results of a standard, not internet-oriented ABC analysis shows the advantage of using the new set of criteria.ABC analysis, internet shop, inventory control

A pilot study on constructing a Scottish sectoral CO2 emissions account

To calculate polluting emissions, the Scottish economy was divided into 76 sectors and the pollution attributable to each sector was estimated. We used emission/output ratios for the UK, but then further adjusted estimated Scottish emissions, using the ratio of economic activity for each sector between Scotland and the UK

Generating varied narrative probability exercises

This paper presents Genpex, a system for automatic generation of narrative probability exercises. Generation of exercises in Genpex is done in two steps. First, the system creates a specification of a solvable probability problem, based on input from the user (a researcher or test developer) who selects a specific question type and a narrative context for the problem. Then, a text expressing the probability problem is generated. The user can tune the generated text by setting the values of some linguistic variation parameters. By varying the mathematical content of the exercise, its narrative context and the linguistic parameter settings, many different exercises can be produced. Here we focus on the natural language generation part of Genpex. After describing how the system works, we briefly present our first evaluation results, and discuss some aspects requiring further investigation

Temporal Reasoning Through Automatic Translation of tock-CSP into Timed Automata

In this work, we present an approach for automatic translation of tock-CSP into Timed Automata (TA) for Uppaal to facilitate using Uppaal in reasoning about temporal specifications of tock-CSP models. The process algebra tock-CSP provides textual notations for modelling discrete-time behaviours, with the support of tools for automatic verification. Automatic verification of TA with a graphical notation is supported by Uppaal. The two approaches provide facilities for automatic verification. For instance, liveness requirements are difficult to specify with the constructs of tock-CSP, but they are easy to specify and verify in Uppaal. We have developed a translation technique and a tool based for translating tock-CSP into a network of small TAs for capturing the compositional structure of tock-CSP. For validating the rules, we begin with an experimental approach based on finite approximations to trace sets. Then, we explore using structural induction to establish the correctness

European Financial System Governance. CEPS Policy Brief, No. 106, 14 June 2006

[From the Introduction]. The intention of this paper is not to make another assessment of the FSAP [Financial Services Action Plan] and its impact,1 but rather to address two subjects. First, we discuss whether decentralisation is here to stay. This structure has its advantages, but creates some unsound asymmetries. Second, there are concepts which, in the aftermath of the FSAP, are beginning to be widely used, but need clarification. Before discussing these issues, we briefly review some facts and patterns of evolution in the European financial system

Library purchasing consortia in the UK: activity, benefits and good practice.

Following a brief introduction in Section 1, Section 2 sets out the operational context of library purchasing consortia. A range of key factors have shaped recent developments in the four LIS sectors under consideration (FE, HE, health and public libraries); some have exerted a common influence over all (e.g. information technology, European Commission purchasing directives, new central government, decline in bookfunds); some are sector-specific (e.g. purchasing arrangements, regional administrative frameworks, collaborative partnerships). The structure and markets of the book and periodical publishing industry in the UK are reviewed, with attention paid to historical as well as more recent practice that has had an impact on library supply. Although each component of the LIS purchasing consortia jigsaw displays individual characteristics that have evolved as a response to its own environment, the thread that links them together is constant change. Section 3 presents the results of a survey of identified library purchasing consortia in the four library sectors. It treats common themes of relevance to all consortia arising from information gathered by seminar input, questionnaire and interview. These include models of consortium operation, membership and governance, ‘typical’ composition of consortia in each sector, and links to analogous practice in other library sectors. Common features of the tendering and contract management process are elicited and attention paid to any contribution of procurement professionals. Finally, levels of consortium expenditure and cost savings are estimated from the published statistical record, which readily demonstrate in financial terms the efficiency of the consortial purchase model for all types of library in the United Kingdom. Section 4 presents the results of a survey of suppliers to libraries in the United Kingdom of books and periodicals, the two sectors most commonly represented in current contracts of library purchasing consortia. It sets out in some detail the operating context governing the highly segmented activities of library booksellers, as well as that pertaining to periodicals suppliers (also known as subscription agents). Detailed responses to questions on the effects of library purchasing consortia on suppliers of both materials have been gathered by questionnaire survey and selected follow-up interviews. Results are presented and analysed according to supply sector with attention given to the tendering process, current contracts under way, cross-sectoral clientele, and advantages and inhibitors of consortia supply. Further responses are reported on issues of how consortia have affected suppliers’ volume of trade, operating margins and market stability as perceived in their own business, the library supply sector and the publishing industry. Finally, overall conclusions are drawn and projections made as to future implications for both types of library suppliers. Section 5 synthesises findings, details enabling and inhibiting factors for consortia formation and models of best practice amongst consortia. The scope for cross-sectoral collaboration is discussed and found to be limited at present. Pointers are given for future activity