Introduction

OGSA-DAI is a middleware product that allows data resources, such as relational or XML databases, to be accessed via web services. An OGSA-DAI web service allows data to be queried, updated, transformed and delivered. OGSA-DAI can be used to provide web services that offer data integration services to clients.

OGSA-DAI web services can be deployed within a Grid environment. OGSA-DAI thereby provides a means for users to Grid-enable their data resources.

Motivation

OGSA-DAI is motivated by the need to:

• Allow different types of data resources - including relational, XML and files - to be exposed onto Grids.
• Provide a way of querying, updating, transforming and delivering data via web services.
• Provide access to data in a consistent, data resource-independent way.
• Allow metadata about data, and the data resources in which this data is stored, to be accessed.
• Support the integration of data from various data resources.
• Provide services that can be combined to provide higher-level web services that support data federation and distributed query processing.
• Contribute to a future in which scientists can move away from technical issues such as handling data location, data structure, data transfer and integration and instead focus on application-specific data analysis and processing.

What Does OGSA-DAI Do?

OGSA-DAI can support the following:

• Different types of data resources - including relational, XML and files - can be exposed via web services. A number of popular data resource products are supported.
• Data within each of these types of resource can be queried and updated.
• Data can be transformed (using XSLT), compressed and decompressed (using ZIP and GZIP compression).
• Data can be delivered to clients, other OGSA-DAI web services, URLs, FTP servers, GridFTP servers, or files.
• Requests to OGSA-DAI web services have a uniform format irrespective of the data resource exposed by the service (though the actions specified within each request may be data resource-specific).
• Provide information about the data resources exposed by an OGSA-DAI web service and the functionality supported by the service to clients.
• OGSA-DAI web services may be extended to expose their own data resources and to support application-specific functionality, in addition to that already provided by this OGSA-DAI distribution.

OGSA-DAI provides web services compliant with two popular web services specifications:

• Web Services Inter-operability (WS-I)
  • http://www.ws-i.org.
  • The WS-I version of OGSA-DAI is compatible with the UK OMII's implementation of WS-I. For more details on OMII and WS-I see: http://www.omii.ac.uk.
• Web Services Resource Framework (WSRF)
  • http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=wsrf.
  • The WSRF version of OGSA-DAI is compatible with the Globus Toolkit's implementation of WSRF. For more details on the Globus Toolkit and WSRF see: http://www-unix.globus.org/toolkit.

Your OGSA-DAI distribution will conform to only one of the above standards and use a specific implementation of it. Check the front page of the user documentation to see which version you have.

OGSA-DAI and DAIS

The DAIS - Database Access and Integration Services - Working Group of the Global Grid Forum (GGF) is formulating standards for database access and integration services.

The development of OGSA-DAI has been occurring in parallel to the development of these specifications. OGSA-DAI influences, and is influenced by, this work. It is intended that OGSA-DAI will eventually provide an implementation of the final version of the DAIS specifications.

Further information on the GGF and DAIS are available from:

• DAIS Working Group:
  • http://forge.gridforum.org/projects/dais-wg.
• Global Grid Forum:
  • http://www.ggf.org.