The Web Eden environment [1,2,3] is an online environment for constructing interactive models that represents a radical new concept in technology-enhanced learning (TEL). By exploiting non-standard principles based on modelling dependency relationships for software construction, it introduces a new paradigm for open source development that blends with the learning experience. Because of its distinctive approach to software construction, Web Eden affords an unusually intimate blending of domain learning with model-building in the spirit of constructivism [7:#100]. This gives unprecedented scope for exploiting the environment to support learning in many different idioms. We can use Web Eden to guide learners through traditional tutorial-like learning material. Web Eden also enables the learner to explore live dynamic artefacts (as opposed to static pages of learning material). If the learners become really advanced, they are able to build their own artefacts and associated learning activities. Web Eden can run as a stand-alone environment, or we can embed it inside a virtual learning environment such as Moodle [7:#106].

Within Web Eden, as in a spreadsheet environment, there are counterparts of meaningful variable quantities ("observables"), defined connections between these which express the ways in which changing the value of one observable directly affects the value of another ("dependencies") and specific instances of redefinition of observables, both manual and automated, that correspond to meaningful action on the part of different agents. The use of dependency is a common - if implicit - feature of much software for educational applications (e.g. tools like Mathematica, The Geometer's Sketchpad, AgentSheets and Matlab, and learning artefacts such as Cabri Geometry and Logotron's Visual Fractions), and its merits are endorsed by the wide range of educational applications for spreadsheets [6]. The motivating idea behind Web Eden is that these merits cannot be fully realised within a conventional conceptual framework for computing [7:#096]. In particular, dependency cannot be integrated into an educational tool based on orthodox software principles (such as Imagine Logo) without compromising its conceptual integrity [7:#102].

In conventional TEL software, there is a clear distinction between the roles of the teacher (a pedagogical expert who conceives and specifies the educational content, interfaces, exercises and learning outcomes), the learner (typically a naive computer user who interacts with the learning environment through a preconceived interface) and the developer (an expert programmer who implements the learning environment). The Web Eden environment is open for interaction in all three roles at all times. What is more, the interaction takes essentially the same form for teacher, learners and developers alike. Every change to the current state to the current environment, no matter how it is to be interpreted (for instance, whether it is a change to the specification of the environment, a step in the learning process, or a revision to the interface or the underlying program), can be expressed as a redefinition of observables in the model. All restrictions upon interaction and interpretation are then of their essence purely discretionary, according to the expertise and interests associated with each specific role. This does not preclude the specification of interfaces to constrain the ways in which particular agents can redefine observables where this is appropriate.

Web Eden is a web-enabled version of the EDEN interpreter [7:#106]. EDEN was web-enabled by Richard Myers in a prize-winning final year project in 2007-8. It exploits state-of-the-art tools that make it possible for server and client machines to share the computational load in interpreting a model. It also overcomes the problems of efficiently interpreting many EDEN models concurrently by enabling distributed processing and load-balancing over many EDEN virtual machines. Many hundreds of models have been built using EDEN [5]. All such model-building has a strong ingredient of domain learning. Many models have an explicit educational objective and the range of learning applications is broad. Web Eden inherits the qualities of EDEN as an educational technology [4], creating a platform for the full realisation of the pedagogical advantages for which previous experience of EDEN has offered proof-of-concept, and helping to overcome the practical obstacles to wider dissemination and adoption. It addresses the portability issues encountered in downloading the interpreter and models, simplifies the integration of the EDEN engine with other applications through the use of web interfaces, and is designed to incorporate session-sharing features that obviate the need to set up networks for collaborative and distributed modes of interaction.

The most comprehensive practical introduction to Web Eden and the modelling principles on which it is based can be found in the workshops prepared in conjunction with The Sudoku Experience - an online activity for gifted and talented pupils organised by the University of Warwick in July 2008 [1]. In these workshops, novice learners are first acquainted with the basic concepts and techniques that are required for model-building. This involves introspecting about the kinds of observables and dependencies that are significant in solving a Sudoku puzzle. They are then shown how these can be related to other tasks, such as devising formulae to convert between different ways of indexing the squares of a Sudoku grid. Once the principles of model-building have been introduced, their application to Sudoku solution is illustrated with reference to a "colour Sudoku" extension and the automation of a technique that is first conceived and implemented as a 'manually executed' pattern of interaction. In the final workshop, the Web Eden environment is configured to allow collaborative concurrent solution of Sudoku puzzles.

Web Eden has also been applied in an online database module under the auspices of the Virtual Studies in Computer Science (ViSCoS) programme at the University of Joensuu, Finland in 2008-9. This has involved integrating Web Eden with the Moodle environment [7:#106]. In the module, design flaws in the international standard relational database language SQL are exposed by contrasting and critiquing different strategies for implementing SQL over a pure relational algebra notation. This practical and interactive approach to highlighting abstract design issues exploits the capacity for implementing additional notations within the Web Eden environment and the scope for open-ended interaction that Web Eden affords.

The Web Eden Sudodu model was re-used in a second-year undergraduate module in December 2008. Alloy, a tool for formal specification developed at MIT, was used to generate the five essentially different abstract mathematical groups of order 8. To make the structure of these groups more accessible, the 9-by-9 grid in the colour Sudoku model was adapted for displaying and manipulating the corresponding group tables [2]. Simple patterns of redefinition and renaming of elements served to acquaint students without specialist mathematical knowledge with the character of a mathematician's intuitive, rather than purely abstract and axiomatic, understanding of group structure.

These examples illustrate that Web Eden is even now ready for use. The environment has recently been further developed to support more sophisticated online use with personal and public project data. The fact that the essential interaction with online models is mediated entirely through definition of observables prepares the ground for several significant extensions. These include: comprehensive monitoring of interactions that enables intermediate states to be recorded and revisited as if "live"; novel possibilities for collaboration primarily mediated through interaction with artefacts rather than communication based on language; potential for graphical user interfaces for fabricating scripts from templates.

We do not envisage the deployment of Web Eden as the release of a product that meets a clearly preconceived specification, but as initiating an organic process of continuing development associated with the progressive extension, refinement and adaptation of existing models and of the environment itself to better meet educational goals. Teachers, developers and learners will all participate in this process. A major concern in TEL has been that of standardisation. In 2002-4, the principles underlying Web Eden were effectively deployed at the BBC R&D Laboratories in resolving critical issues of portability of digital content. This gives us confidence that, appropriately deployed, Web Eden can offer rich experiences customised to diverse learners and contexts. To achieve this goal, we aspire to establish an online Centre for Constructivist Computing that promotes the creation of models, teaching and learning strategies, and extensions and refinements of the modelling tool through open source development that brings together representatives from schools, universities and industry worldwide.

References

1. http://www.dcs.warwick.ac.uk/~wmb/sudokuExperience/workshops/
2. http://www.dcs.warwick.ac.uk/~wmb/webeden/Group8OpenDayNov2008.html
3. http://www.dcs.warwick.ac.uk/~wmb/webeden/puzzle.html
4. http://www2.warwick.ac.uk/fac/sci/dcs/research/em/applications/educationaltech/
5. http://empublic.dcs.warwick.ac.uk/projects/
6. J.E.Baker, S.J.Sugden, Spreadsheets in Education: The First 25 Years, Spreadsheets in Education, 2003.
7. Papers as indexed at: http://www2.warwick.ac.uk/fac/sci/dcs/research/em/publications/papers/
   Paper #106 is at http://www2.warwick.ac.uk/fac/sci/dcs/research/em/publications/papers/106/ etc