The International Virtual Observatory Alliance (IVOA)[1] is a worldwide scientific organisation formed in June 2002. Its mission is to facilitate international coordination and collaboration necessary for enabling global and integrated access to data gathered by astronomical observatories. An information system allowing such an access is called a virtual observatory. The main task of the organisation so far has focused on defining standards to ensure interoperability of the different virtual observatory projects already existing or in development.
The IVOA now comprises 19 VO projects from Argentina, Armenia, Australia, Brazil, Canada, China,Europe, France, Germany, Hungary, India, Italy, Japan, Korea, Russia, Spain, Ukraine, theUnited Kingdom, and the United States. Membership is open to other national andinternational projects according to the IVOA Guidelines for Participation.
Senior representatives from each national VObs project form the IVOA ExecutiveCommittee. A chair is chosen from among the representatives and serves a 1.5year term, preceded by a 1.5 year term as deputy chair. The ExecutiveCommittee meets 3-4 times a year to discuss goals, priorities, and strategies.
IVOA currently brings together nineteen member organisations, both national and international :
The tasks of the IVOA are distributed over different working groups:
The IVOA Applications Working Group is concerned primarily with the software tools that Astronomers use to access VO data and services for doing Astronomy.The role of the Applications Working Group is to:
The task of the Data Access Layer (DAL) working group is to define and formulate VO standards forremote data access. Client data analysis software will use these services toaccess data via the VO framework; data providers will implement these servicesto publish data to the VO.
The DAL working groups has defined various standards for accessing data sets, inparticular images (Simple Image Access Protocol, SIAP6), spectra (Simple SpectraAccess Protocol, SSAP7) and source catalogues (Simple Cone Search, SCS8).
The role of the Data Modelling Working Group is to provide a framework for the descriptionof metadata attached to observed or simulated data.The activity of the Data Model WG activity focuses on logical relationshipsbetween these metadata, examines how an astronomer wants to retrieve,process and interpret astronomical data, and provides an architecture to handlethem. What is defined in this WG can then be re-used in the protocols defined bythe DAL WG or in VO aware applications.
The aim of the Grid and Web Services(GWS) Working Group is to define the use of Grid technologies and webservices within the VO context and to investigate, specify, and implementrequired standards in this area. This group was formed from a merger of the WebServices group and the Grid group, ordered at the IVOA Executive meeting heldduring the IAU General Assembly in 2003.
The Resource Registry Working Group defines the structure and interface to an IVOA Registry. Sucha registry “ … will allow an astronomer to be able to locate, get details of, andmake use of, any resource located anywhere in the IVO space, i.e. in any VirtualObservatory. The IVOA will define the protocols and standards whereby differentregistry services are able to interoperate and thereby realise this goal.”
The Semantics Working Group will explore technology in the area ofsemantics with the aim of producing new standards that aid the interoperability ofVO systems. The Semantics Working Group is concerned with the meaning or theinterpretation of words, sentences, or other language forms in the context ofastronomy. This includes standard descriptions of astrophysical objects, datatypes, concepts, events, or of any other phenomena in astronomy. The WGcovers the study of relationships between words, symbols and concepts, as wellas the meaning of such representations (ontology). The WG covers use of naturallanguage in astronomy, including queries, translations, and internationalization ofinterfaces.
The VO Query Language (VOQL) Working Group will be in charge of defining a universal QueryLanguage to be used by applications accessing distributed data within the VirtualObservatory framework.
The VOTable Working Group is in charge of the VOTable format, whichis an XML standard for the interchange of data representedas a set of tables.[2] In this context, a table is an unordered set of rows, each of auniform format, as specified in the table metadata. Each row in a table is asequence of table cells, and each of these contains either a primitive data type, oran array of such primitives. VOTable is derived from the Astrores format,itself modelled on the FITS Table format; VOTable was designed to be closerto the FITS Binary Table format.
During the IVOA executive meeting of January 2004 in Garching, Germany, theIVOA Theory Interest Group (TIG) was formed with the goal of ensuring that theoreticaldata and services are taken into account in the IVOA standards process.By its charter, the IVOA Theory Interest Group intends to: