The impact

OGSA-DAI is software for managing data that is distributed over different databases (and other data sources). Although many people want the functionality that OGSA-DAI provides, some new users had found difficulties in using and maintaining the software. The Software Sustainability Institute developed OGSA-DAI to address these issues - even for novice users.

The usability of OGSA-DAI was improved by developing a more intuitive user interface and providing the software preconfigured on a virtual machine, which makes it easier to download and start the software. The maintainability was addressed by developing OGSA-DAI to use the Graphiti Eclipse framework, which is a more intuitive interface for developing and maintaining code. The software was also made available on SourceForge, which is a first step towards developing a community around OGSA-DAI.

This work was completed in conjunction with the ADMIRE project.

The problem

OGSA-DAI is an application that provides Web Service-based wrappers to various types of data, e.g. relational data, with a built-in extensible streaming data access and integration workflows engine that allows workflows to run close to the data. These workflows can perform complex tasks - for example, you could get data from a database and merge it with data obtained from another public source and then send the result to a third party. OGSA-DAI provides developers with a framework whose basic functionality can be extended to build much more powerful capabilities such as a (relational) distributed query processing that can take relational data from various other services and perform sophisticated joins and other types of operations that provide federation capabilities to distributed data mediated through OGSA-DAI services.

OGSA-DAI was adopted by the EU funded ADMIRE project, which constructed a platform for researchers who perform data-intensive research. ADMIRE used OGSA-DAI and some other services to abstract away from the underlying resources allowing domain experts to effectively view the distributed data they were interested in as though it were a single federated resource. To operate within this framework domain experts would work together with ADMIRE developers to produce canonical workflows using a new language called DISPEL to facilitate this process. These workflows could be used by the appropriate community to undertake its research.

To further simplify the process of building complex workflows a visual workflow builder was written within the ADMIRE project. This used Eclipse as the base system with the Graphical Modelling Framework to do the visualisation and code generation within the Eclipse platform. However, this was found to be cumbersome and difficult to both use and extend. So with funding from JISC and help from the Software Sustainability Institute the workbench was made more usable and maintainable and an open development process was adopted to make the software more accessible to other interested parties.

The solution

The solution consisted of two types of review:

• The first involved reviewing the maintainability of the OGSA-DAI work bench code. This revealed significant challenges in understanding how it works and how to modify or extend it. In the end it was decided to be easier to refactor the workbench to use Graphiti, a new Eclipse framework developed by SAP.
• The second type of review was a usability evaluation, specifically an expert heuristic evaluation. This was done in two iterations and the results of the evaluation used to guide improvements of the usability of the workbench.

The workbench was put in SourceForge which would both help in the workbench's long term sustainability. To give people to quickly try out the software without having to undertake the onerous task of setting up an ADMIRE framework together with the required OGSA-DAI services a test system was made available in a VMware virtual machine (VM) image. So, if you would like to try out the OGSA-DAI visual workbench all you have to do is download the VM from SourceForge, kick-it up using a VMware player and follow the tutorial included in the image.

The OGSA-DAI Visual Workbench is now in a much better position to be developed in the future thanks to JISC funding and help from the Software Sustainability Institute.

To try out the visual workbench you can download the Workbench VM from:

• http://sourceforge.net/projects/admire/files/

The development of this project was also blogged and provides insights into the decisions made during the project.