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SUMMARYInitially, Grid technologies were principally associated with supercomputer centres and large-scale scientific applications in physics and astronomy. They are now increasingly seen as being relevant to many areas of e-Science and e-Business. The emergence of the Open Grid Services Architecture (OGSA), to complement the ongoing activity on Web Services standards, promises to provide a service-based platform that can meet the needs of both business and scientific applications. Early Grid applications focused principally on the storage, replication and movement of file-based data. Now the need for the full integration of database technologies with Grid middleware is widely recognized. Not only do many Grid applications already use databases for managing metadata, but increasingly many are associated with large databases of domain-specific information (e.g. biological or astronomical data). This paper describes the design and implementation of OGSA-DAI, a service-based architecture for database access over the Grid. The approach involves the design of Grid Data Services that allow consumers to discover the properties of structured data stores and to access their contents. The initial focus has been on support for access to Relational and XML data, but the overall architecture has been designed to be extensible to accommodate different storage paradigms. The paper describes and motivates the design decisions that have been taken, and illustrates how the approach supports a range of application scenarios. The OGSA-DAI software is freely available from http://www.ogsadai.org.uk.

This paper presents the identification of a new programming language concept and reports our initial investigations of its utility. The concept is to identify persistence as an orthogonal property of data, independent of data type and the way in which data is manipulated. This is expressed by the principle that all data objects, independent of their data type, should have the same rights to persistence or transience. We expect to achieve persistent independent programming, so that the same code is applicable to data of any persistence. We have designed a language PS-algol by using these ideas and constructed a number of implementations. The experience gained is reported here, as a step in the task of achieving languages with proper accommodation for persistent programming.

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International audienceThis special issue and our editorial celebrate 10 years of progress with data-intensive or scientific workflows. There have been very substantial advances in the representation of workflows and in the engineering of workflow management systems (WMS). The creation and refinement stages are now well supported, with a significant improvement in usability. Improved abstraction supports cross-fertilisation between different workflow communities and consistent interpretation as WMS evolve. Through such re-engineering the WMS deliver much improved performance, significantly increased scale and sophisticated reliability mechanisms. Further improvement is anticipated from substantial advances in optimisation. We invited papers from those who have delivered these advances and selected 14 to represent today's achievements and representative plans for future progress. This editorial introduces those contributions with an overview and categorisation of the papers. Furthermore, it elucidates responses from a survey of major workflow systems, which provides evidence of substantial progress and a structured index of related papers. We conclude with suggestions on areas where further research and development is needed and offer a vision of future research directions

Recent HCI research has produced analytic evaluation techniques which claim to predict potential usability problems for an interactive system. Validation of these methods has involved matching predicted problems against usability problems found during empirical user testing. This paper shows that the matching of predicted and actual problems requires careful attention, and that current approaches lack rigour or generality. Requirements for more rigorous and general matching procedures are presented. A solution to one key requirement is presented: a new report structure for usability problems. It is designed to improve the quality of matches made between usability problems found during empirical user testing and problems predicted by analytic methods. The use of this report format is placed within its design research context, an ongoing project on domain-speci® c methods for software visualizations.

The language Java is enjoying a rapid rise in popularity as an application programming language. For many applications an effective provision of database facilities is required. Here we report on a particular approach to providing such facilities, called "orthogonal persistence". Persistence allows data to have lifetimes that vary from transient to (the best approximation we can achieve to) indefinite. It is orthogonal persistence if the available lifetimes are the same for all kinds of data. We aim to show that the programmer productivity gains and possible performance gains make orthogonal persistence a valuable augmentation of Java.

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