Technical specifications

APIs, Standards and Services for data publishing used

Data publishing requires as well community specific standards, which in astronomy are covered by the International Virtual Observatory Alliance (IVOA)

Additionally, there are is the Open Archive Initiative - Protocol for Metadata Harvesting (OAI-PMH), which some of the VO specifications employ. And OAI-PMH is a basis for exchanging metadata with other domains.

Virtual Observatory Specifications

The VO specifications comprise more than 50 different specifications, with additional notes adressing topics crossing various of the specifications or adressing a special realm. We mention here only those which are implemented in the Daiquiri framework and relevant for Gaia @ AIP.

Cone search API:

Very standard question: What information in a catalog is available, given a point in the sky, and in a circle surroundig this point? The Cone Search API specifies a VO service for this.

VO Table

The VO Table specifies a metadata rich table format using XML. It is the reference return format for all VO services providing tabular data. Metadata, used coordinate systems, time information, and data descriptors of a VO Table are expected to conform to other VO specifications. _This is makes VOTable data machine readable and interoperable (within the astronomy domain). _


The Astronomical Data Query Language specifies a subset of the SQL language, adding features, which provide easy queries for standard astronomical problems (implementing geometrical forms in spherical coordinates).

Table Access Protocol (TAP)

A very substantial part of astronomical data is tabular data. TAP is the main API for scripted access to published tabular data, and the standard TAP query language is ADQL. The most versatile implementation of TAP is PyVO, providing access to remote data and services of the Virtual Observatory (VO) using Python. PyVO is part of astropy .

Data Link

The Data Link service enables to not only return e.g. the table data of a query, but also available additional data from directly connected other data available at a site (here Gaia @ AIP).

VO Registry Interface

The VO Registry Interface specifies requirements for a site (here Gaia @AIP) to provide information to the distributed "Registries of Registries", which enable VO capable applications to operate across many data publishers in astronomy.

Other services


Based on the Open Archive Initiative - Protocol for Metadata Harvesting (OAI-PMH) specification, the framework delivers an interface to query available metadata for a dataset, either for the VO registry, or for other cross community data archives (e.g. Europeana) and document services, and also for DataCite.


For published data we provide Digital Object Identifiers (DOI). These DOI make the data 'citable', avoid the 'stale links' problem, and cross community useable metadata. The DOI information is delivered via the OAI-PMH protocol. Meanwhile, VO tables can carry DOI as part of their metadata. It's very useful support for making the data FAIR.