TAP (Table Access Protocol)
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| TAP (Table Access Protocol) | |
|---|---|
| Name | Table Access Protocol |
| Abbreviation | TAP |
| Developer | International Virtual Observatory Alliance |
| Introduced | 2009 |
| Latest release | 1.1 |
| License | Open standard |
| Website | International Virtual Observatory Alliance |
TAP (Table Access Protocol) is a network protocol standard for querying and retrieving tabular astronomical data from remote services. It was developed to enable uniform access to catalogs, survey tables, and mission archives across distributed archives and observatories. TAP defines how clients and servers exchange queries, results, metadata, and capabilities to support interoperable data discovery and analysis.
Overview
TAP originated within the International Virtual Observatory Alliance effort alongside initiatives such as the Virtual Observatory projects, European Space Agency archives, NASA mission archives, Sloan Digital Sky Survey, Two Micron All-Sky Survey, and other observatory data centers. The protocol standard aligns with services provided by institutions like the Centre de Données astronomiques de Strasbourg, Space Telescope Science Institute, European Southern Observatory, National Radio Astronomy Observatory, and Japan Aerospace Exploration Agency data centers. TAP complements related standards including VOTable, ADQL, SAMP, and VOResource, and interacts with registries such as the Virtual Observatory Registry and catalogs from missions like Gaia, Hubble Space Telescope, Chandra X-ray Observatory, Spitzer Space Telescope, and Kepler.
Protocol Specification and Architecture
TAP specifies an HTTP-based service interface influenced by web standards used by organizations such as the World Wide Web Consortium, Internet Engineering Task Force, European Organization for Nuclear Research, and archives like HEASARC. Its architecture defines endpoints for synchronous and asynchronous queries, leveraging job control patterns similar to Universal Worker Service and employing formats like VOTable for results. TAP servers publish capabilities and metadata through registry records used by clients developed at places like AstroGrid, Aladin, TOPCAT, IRAF, CASA, and STILTS. TAP services are frequently deployed on platforms maintained by institutions such as NASA Ames Research Center, Max Planck Institute for Astronomy, Johns Hopkins University, Harvard–Smithsonian Center for Astrophysics, and Leiden Observatory.
Query Languages and Data Models
TAP supports multiple query languages and data models centered on Astronomical Data Query Language (ADQL), which combines elements of SQL dialects used by database systems like PostgreSQL, MySQL, Oracle Database, Microsoft SQL Server, and SQLite. ADQL includes astronomy-specific constructs such as cone searches and geometric functions that reference coordinate frames used by missions like Gaia and surveys like Pan-STARRS. TAP also supports plain SQL, parameterized queries, and table upload mechanisms compatible with formats from tools like TOPCAT, Astropy, Pandas (software), NumPy, MATLAB, and R (programming language). Data models referenced in TAP implementations draw on schemas from IVOA Observation Data Model, IVOA Characterisation Data Model, and archive-specific conventions used by Sloan Digital Sky Survey and Galex.
Implementations and Client Software
Major server implementations of TAP are provided by projects and institutions including DaCHS, TAPlib, GAVO, AstroGrid, CDS services, VO-Paris, and research groups at European Southern Observatory, National Centre for Supercomputing Applications, Leiden University, and INAF. Client software supporting TAP queries includes TOPCAT, Aladin, STILTS, AstroPy, VOClient, SPLAT-VO, PyVO, VOSpec, and analysis environments at NASA Goddard Space Flight Center, CERN collaborations, and university data centers. Workflow systems and science platforms like Jupyter, CASA, IRAF, and grid middleware projects integrate TAP access for cross-mission analysis.
Use Cases and Applications
TAP is used for cross-matching catalogs from projects such as Gaia, Sloan Digital Sky Survey, 2MASS, WISE, Pan-STARRS, LSST, UKIDSS, FIRST, and NVSS; for retrieving time-series and light-curve tables from missions like Kepler and TESS; and for accessing spectral tables from observatories including Chandra, XMM-Newton, Spitzer, and Herschel. Scientific applications span studies by groups associated with European Space Agency programmes, NASA science teams, university consortia, and projects funded by agencies such as the National Science Foundation, European Commission, JAXA, and CNES. TAP supports services for multi-wavelength data fusion, transient-event follow-up used by collaborations like Zwicky Transient Facility and LSST Science Collaboration, and archival research for missions such as Herschel and Planck.
Security, Authentication, and Access Control
TAP deployments implement authentication and authorization mechanisms aligned with infrastructure from Internet2, EduGAIN, OAuth 2.0, OpenID Connect, and certificate frameworks like those used by European Grid Infrastructure and XSEDE. Service providers often integrate with institutional identity providers at organizations such as ESA, NASA, CNRS, Max Planck Society, and university federations to control access to proprietary tables, embargoed datasets, and proprietary mission products. TAP defines mechanisms for secure token exchange, role-based access control as practiced at archive centers like STScI and ESO, and supports transport security via TLS.
Interoperability and Extensions
TAP is part of the IVOA ecosystem alongside standards like VOTable, UWS, SAMP, VOEvent, VOResource, ObsCore, and SIAP. Extensions and profiles have been developed in collaboration with projects such as AstroGrid, GAVO, Europlanet, ALMA, and archives including Herschel Science Centre and XMM Science Archive to support features like asynchronous processing, table uploads, region queries, and provenance integration with models from W3C and PROV. Continued interoperability work involves collaborations with initiatives at CERN, CODATA, RDA, and major observatory consortia to harmonize TAP with evolving data platforms and cloud-native archives.