The International Virtual Observatory Alliance (IVOA: http://www.ivoa.net) represents 14 international projects working in coordination to realize the essential technologies and interoperability standards necessary to create a new research infrastructure for 21st century astronomy. This international Virtual Observatory will allow astronomers to interrogate multiple data centres in a seamless and transparent way, will provide new powerful analysis and visualisation tools within that system, and will give data centres a standard framework for publishing and delivering services using their data. The first step for the IVOA projects is to develop the standardised framework that will allow such creative diversity. Since its inception in June 2002, the IVOA has already fostered the creation of a new international and widely accepted, astronomical data format (VOTable) and has set up technical working groups devoted to defining essential standards for service registries, content description, data access, data models and query languages following developments in the grid community. These new standards and technologies are being used to build science prototypes, demonstrations, and applications, many of which have been shown in international meetings in the past two years. This paper reviews the current status of IVOA projects, the priority areas for technical development, the science prototypes and planned developments.
For the Virtual Observatory to connect archives around the globe, some standardization is needed. It is not necessary to rework the internal structure of each archive to a common standard, but standards for interfaces to archives and for exchange of data are important.
We report on standardization work currently going on in the AVO and AstroGRID projects in the following areas:
- Exchange formats for tabular data;
- Semantic definitions for quantities in tabular data;
- Identification of user and authorization to use resources;
- Query interfaces to archives;
- Catalogues of data resources.
Discussion on standards is ongoing among all Virtual Observatory projects.
AVO Work Area 2 consists of deployment and demonstration of an interoperability prototype. Access to archives of all the partners (ESO, ESA, AstroGrid, Terapix, Jodrell Bank) is implemented via the CDS data federation and integration tools: VizieR and Aladin. The prototype is available for science usage and more functionalities, based in particular on the usage of Uniform Content Descriptors (UCDs) for data mining, will be developed. Case by case discussion with data providers will help to establish a set of practical recommendations for interoperability. Science requirements and new technologies studied by the other AVO work Areas will also be tested. Discussions on standards are ongoing among all VO projects.
Building an automated classifier for high-energy sources provides an opportunity to prototype approaches to building the Virtual Observatory with a substantial immediate scientific return. The ClassX collaboration is combining existing data resources with trainable classifiers to build a tool that classifies lists of objects presented to it. In our first year the collaboration has concentrated on developing pipeline software that finds and combines information of interest and in exploring the issues that will be needed for successful classification.
ClassX must deal with many key VO issues: automating access to remote data resources, combining heterogeneous data and dealing with large data volumes. While the VO must attempt to deal with these problems in a generic way, the clear science goals of ClassX allow us to act as a pathfinder exploring particular approaches to addressing these issues.
The Astrophysical Virtual Observatory Project (AVO: http://www.eso.org/projects/avo/) will conduct a research and demonstration program on the scientific requirements and technologies necessary to build a VO for European astronomy. The AVO has been jointly funded by the European Commission and six European organizations for a three year Phase-A work program valued at 5 million Euro. The Phase A program will focus its work in three areas -- science requirements, archive interoperability and GIRD/database technologies. The AVO project, the US NVO and UK ASTROGRID projects have been working closely together over the past nine months to reach consensus on essential technical directions and standards that will facilitate the possibility of an International Virtual Observatory. An International Virtual Observatory Alliance was formed in June 2002 among all currently funded and proposed VO projects. The IVOA has adopted a roadmap for IVO developments over the next three years that will feature coordinated demonstrations of VO capabilities on specific science programs, and international agreements on key interoperability standards and tools.
Interoperability is one of the important issues in the current efforts to build the Virtual Observatory. We present here some of the tools which already contribute to the efficient exchange of information between archives and databases.
The Centre de Donnees astronomiques de Strasbourg (CDS) develops a set of value-added services, widely used for information retrieval, observation preparation, data interpretation, etc. SIMBAD, VizieR, Aladin and the 'Dictionary of Nomenclature' integrate heterogeneous selected information from observatory archives, sky surveys and publications. Each service organizes information in a different way (astronomical objects, tables, images with overlays), and the CDS hub allows versatile information retrieval, e.g. looking for known information in a given region of the sky, including observations from ground- and space-based instruments, or searching by criteria in large data sets. Links among the CDS services, and with other reference on-line information systems, such as observatory and survey archives or publications, permit comprehensive searches in a wide variety of resources. Shared exchange standards and generic tools such as the GLU are essential for the building of links. XML is a key tool for further information integration, and Aladin is a precursor of an integration tool, relying on FITS and XML. New functionalities will be developed at CDS in the context of the Virtual Observatory, e.g. for data mining and management of very large catalogues.
The REMOT (Remote Experiment Monitoring and conTrol) project was financed by 1996 by the European Community in order to investigate the possibility of generalizing the remote access to scientific instruments. After the feasibility of this idea was demonstrated, the DYNACORE (DYNAmically, COnfigurable Remote Experiment monitoring and control) project was initiated as a REMOT follow-up. Its purpose is to develop software technology to support scientists in two different domains, astronomy and plasma physics. The resulting system allows (1) simultaneous multiple user access to different experimental facilities, (2) dynamic adaptability to different kinds of real instruments, (3) exploitation of the communication infrastructures features, (4) ease of use through intuitive graphical interfaces, and (5) additional inter-user communication using off-the-shelf projects such as video-conference tools, chat programs and shared blackboards.