Technical Terms & Acronyms

This is a document intended for deployers of VO services. This is also a document in progress. IVOA members help to keep this glossary of technical terms used in the VO current and correct. We thank you for your contribution!

Term	Description
Capability	What a service can do - i.e. whether it offers a cone search service, or a TAP service, or a plain web interface, etc. A service can offer more than one capability.
SkyView	Web site and VO-enabled distributable tool that generates images from survey data.
SkyServer	Web service that presents data from the Sloan Digital Sky Survey.
VODataService	VODataService refers to an XML encoding standard for a specialized extension of the IVOA Resource Metadata that is useful for describing data collections and the services that access them.
Mirage	VO-enabled tool for exploratory analysis and visualization of images and multi-dimensional numerical data.
VOResource	VO Rsource describes an XML encoding standard for IVOA Resource Metadata.
UCD	Unified Content Descriptor. A standard vocabulary for describing astronomical data quantities. It does not specify the name of a quantity, or its units, but rather what type of quantity it is. For example, a column in table might have the name "T-kin" and the UCD "phys.temperature" which states that it represents a temperature, but does not imply a specific unit.
Parse	To separate into more easily understood parts.
Query	To interrogate a collection of data such as records in a database.
TDIG	Time Domain Interest Group
Theory IG	Theory Interest Group
Registry	The “yellow pages” for the VO. Collects and stores basic information about archives, data collections, databases, and other resources.
VOSI	The VO Support Interface describes the minimum interface that a web service requires to participate in the IVOA.
Source code	The version of a program normally written or edited by a programmer and either compiled into an executable program, or run directly using an interpreter (see interpreted languag).
UWS	The Universal Worker Service (UWS) pattern defines how to manage asynchronous execution of jobs on a service.
SODA	The SODA web service interface defines a RESTful web service for performing server-side operations and processing on data before transfer.
SLAP	The Simple Line Access Protocol (SLAP) is an IVOA Data Access protocol which defines a protocol for retrieving spectral lines coming from various SpectralLine Data Collections through a uniform interface within the VO.
Footprint	The region of the sky that has been observed by one or more telescopes.
ProvenanceDM	The Provenance Data Model describes how provenance information can be modeled, stored and exchanged within the astronomical community in a standardized way.
Operating system	The program framework in which all other programs run on a computer, e.g. Windows XP, MacOS? X, Linux, etc.
Serialization	The process of converting an object into a format that can be stored or transmitted across a network.
PhotDM	The Photometry Data Model (PhotDM) standard describes photometry filters, photometric systems, magnitude systems, zero points and its interrelation with the other IVOA data models through a simple data model.
Architecture	The overarching design of a computer, network, or software system.
ObsLocTAP	The Observation Locator Table Access Protocol (ObsLocTAP) defines a data model for scheduled observations and a method to run queries over compliant data, using several Virtual Observatory technologies.
ObsCoreDM	The Observation Core components Data Model describes the core metadata common to most data products distributed for astronomical observations. It is the common basis that helps to search and discover datasets across various VO compatible archives via a customized TAP protocol: ObsTAP
MOC	The Multi-Order Coverage map is an IVOA standard to manipulate coverages in order to provide very fast union, intersection and equality operations between them. It is based on the healpix tesselation.
Resource metadata	The metadata that describes services and data resources available in the VO.
Socket	The low-level software element that makes a connection to the network. Normally a client connects to a socket on a server.
RegTAP	The IVOA Registry Relational Schema defines an interface for searching this resource metadata based on the IVOA's TAP protocol.
HiPS	The Hierarchical Progressive Survey aims to enable dedicated client/browser tools to access and display an astronomical survey progressively, based on the principle that “the more you zoom in on a particular area the more details show up”. It is based on the healpix tessellation.
Semantics	The expression of the meaning of symbols or names. In the VO, the actual scientific meaning of data and services.
Federation	The dynamic combination of information from separate sources of information.
DALI	The Data Access Layer Interface (DALI) defines resources, parameters, and responses common to all DAL services so that concrete DAL service specifications need not repeat these common elements.
Platform	The combination of a computer’s operating system software and hardware.
Interoperability	The ability of software and/or hardware on different machines from different vendors or sources to share data or collaborate without special effort on the part of the user.
ObsTAP	TAP interface to ObsCoreDM
TAP	Table Access Protocol. TAP services provide query-driven access to astronomical tables and databases. For example, whereas a simple cone-search allows you to search only by sky position, and returns a fixed set of columns, a TAP service allows to make searches along the lines of "give me all the records with B-V>2.0 and give me just columns B, D, F, and G". Queries need to be formulated in the standard ADQL, but often the tool you are using will construct this for you.
SCSP	Standing Committee on Standards and Processes
Distributed computing	Spreading the workload for processing tasks over multiple machines.
Service	Something on the internet which will actively do somethin, as opposed to being a passive repository of information. For example, an image service may have a large atlas of images, but also offers a way of submitting a query to get back a cut-out image from a particular piece of sky.
Solar IG	Solar Systems Interest Group
Open source	Software, usually free, created by a development community where the source code is distributed as well as compiled code.
Agent	Software that acts or works on behalf of a user.
Web service	Software available over the web using a standardized XML messaging system.
Semantics WG	Semantics Working Group
WS	see web service
Asynchronous services	See Synchronous/Asynchronous services
Simple Spectral Access	See SSAP.
Cone search	See SCS.
XMatch	see crossmatch
Callbacks	Routines that are automatically invoked when some event occurs or situation is encountered.
Registry WG	Resource Registry Working Group
Radio IG	Radio Interest Group
Object-oriented	Programming based on the concept of an “object”, a data structure associated with specific routines that define the behavior of the object.
Operations IG	Operations Interest Group
Carnivore	Open source registry developed at Caltech, supporting publishing, searching, and harvesting. Primarily intended for use by data providers who want to set up their own registry.
Sexagesimal	Numeral system with number 60 as the base.
SQL Server	Microsoft’s RDBMS software.
SAMP	Messaging protocol that allows applications to exchange messages and data between each other through a central hub, which is a tiny application that runs on the user's desktop. For example, you might have retrieved a catalogue from a cone search service using Topcat, but also have an image tool such as Aladin or DS9 running, looking at an image of the same piece of sky. Topcat can then send the table to the image tool, which can overplot the objects on the image.
Grid	Massive distributed computing capabilities currently available on the Internet.
Single Sign On	Many datasets in the VO are public, but many have some proprietary restrictions, that need a user to specify who they are, and for the service to work out if they are allowed access. The idea behind single sign-on is that you should only have to sign-on once per session, and have your credentials passed around as necessary. The technical infrastructure for this is agreed but not yet fully implemented.
KDDIG	Knowledge Discovery Interest Group
TCG	IVOA Technical Coordination Group
CSP	IVOA Standing Committee on Science Priorities
Units	IVOA standardised strings to specify the units of a quantity. At the time of writing this is in the final stages of agreement by the IVOA.
Exec	IVOA Executive Committee
Parameters	Inputs to or elements in a system which can be varied.
Metadata	Information or labels that describe data.
Authentication	In computer security, verification of the identity of a user and/or the user's eligibility to access a service.
GWSWG	Grid and Web Services Working Group
Wget	Free software package for retrieving files using HTTP, HTTPS and FTP.
Crossmatch	Find objects from two or more datasets that are near each other in the sky.
EduIG	Education Interest Group
Datalink	DataLink is a data access protocol with the purpose to provide a mechanism to link resources found via one service to resources provided by other services.
Virtual data	Data product that is dynamically generated when needed.
DMWG	Data Modelin Working Group
DCPIG	Data Curation and Preservation Interest Group
DALWG	Data Access Layer Working Group
HTTP	Communications protocol used to access most web pages.
Peer-to-peer	Communication between two or more computers where the protocol is symmetric between the participants so that each participant can make the same requests or give the same responses. This contrasts with client-server protocols
Code stubs	Code, usually generated by software tools, which defines the interfaces to some component but typically does not include any implementation of its functionality.
PyVO	Astropy affiliated package providing access to remote data and VO services using Python.
Bindings	Associations between defined web interfaces and the services that provide them.
ASDM	Archive Science data model : a data format for ALMA , EVLA data
Grid computing	Applying the resources of many computers in a network to a single problem at the same time.
AppsWG	Applications Working Group
Instance document	An XML document that conforms to a schema.
VOTable	An XML -based encoding scheme for astronomical tables and catalogs, established by the IVOA in order to provide an unambiguous way to transmit tables between computer programs
MySQL	An open source SQL relational database management system (RDBMS).
Java	An object-oriented, platform-independent programming language, developed by Sun, and modeled after C++.
C++	An object-oriented version of the C programming language.
Ruby	An object-oriented programming language.
IVOA identifiers	An IVOA Identifier is a globally unique name for a resource within the Virtual Observatory.
Token	An item in a string of text that can be separated out by a parser, such as a single word in a sentence or a number in a comma-delimited list.
Middleware	An intermediate level of computer software typically used to provide a common interface to heterogeneous lower level components.
Aladin	An interactive tool that allows the user to visualize digitized images and catalogs from many sources.
TOMCAT	An HTTP server that can run Java servlets.
HTTP POST	An HTTP request where data is sent to the server.
HTTP GET	An HTTP request where any parameters of the request are included in the URL itself.
Container	An element that acts as a parent and contains child elements.
Certificate	An electronic document that verifies the owner of a public key, issued by a certificate authority.
DataScope	A web-based VO tool that finds information from many VO sources near a specified point in the sky.
SkyPortal	A web site that supports translation of a user ADQL query into queries of one or more SkyNodes.
Portal	A web site that serves as a starting point to other destinations or services on the web.
SESAME	A web service interface to the SIMBAD name resolver.
Treeview	A VO-enabled viewer for hierarchical file structures.
WESIX	A VO web service to the standard astronomical image analysis package SExtractor together with a crossmatching service.
WCS Fixer	A VO web service that corrects the WCS information in a given FITS image.
VOPlot	A VO Tool for visualizing astronomical data from VOTable sources.
VOEvent	A VO standard for representing, transmitting, publishing and archiving the discovery of a transient celestial event.
OpenSkyQuery	A VO Service that enables crossmatching of astronomical catalogs and selection of catalog subsets.
SCS	A VO protocol that requests information near a specified location in the sky.
SkyNode	A VO protocol (and the services that implement it) that provides an ADQL interface to astronomical databases.
VOStat	A VO and web-enabled statistics package.
Mosaic, mosaicking	A virtual observation made by combining multiple observations at different positions resulting in a combination of images that abut and/or overlap into a single larger image.
Vizier	A very large collection of astronomical catalogues and tables stored at CDS, Strasbourg. As well as well known catalogues, it includes many tables published as part of astronomical papers. Vizier catalogues and tables can be accessed through the CDS web pages, or through several different VO tools.
Validator	A tool that checks some element of a system for conformance to a standard.
Synchronous/Asynchronous services	A synchronous service is one where the user needs to stay connected to a remote service and interact with it in real time, whereas with an asynchronous service the user specifies a job to be done, disconnects and collects the result later. For this to work, the IVOA has agreed a standardised way of describing a job, and the current state of a job.
Interface	A structured interaction between two entities, often a client and a server.
IVORN, IVOA identifier	A standardized, unique ID used in a number of contexts within the VO.
XQuery	A standard language for querying XML data.
VOClient	A software suite callable from many languages which implements data access in the VO.
Applet	A small program that runs in a larger client context, often Java programs embedded in Web pages.
Script	A simple program usually written in an interpreted language.
Protocol	A set of rules that define the interactions between two or more components.
Name resolver	A service that translates object names into astronomical coordinates.
Workflow	A sequence or network of tasks and associated information needed to pass from one task to another to accomplish some goal.
HTTPS	A secure version of the HTTP protocol.
Cyberinfrastructure	A research environment in which advanced computational services are available to researchers through high-performance networks.
Interpreted language	A programming language that is parsed and executed without needing any explicit compilation.
Perl	A programming language frequently used for web scripts and to process data passed via HTML forms.
Servlet	A program, typically Java, that runs on a web server in response to a web request.
Daemon	A program or process that runs in the background unattended and may be invoked by another process to perform its function.
Proxy	A piece of software that acts on behalf of a user or another piece of software. An agent is a client proxy.
VOEventNet	A peer-to-peer cyberinfrastructure to enable rapid and federated observations of the dynamic night sky.
Markup language	A language for annotating a document to enable each component to be appropriately formatted, displayed, or used.
Ant	A Java -based software build tool, similar to Unix ""make"".
Ontology	A formal description of the vocabulary used in a field, especially describing the relationships between various concepts within that subject.
Data model	A formal description of how data may be structured and used.
VOSpace	A distributed storage concept for the VO.
Distributed database	A database where the underlying data is stored on multiple servers.
Relational database	A database that stores data in a structure consisting of one or more tables (aka relations) of rows and columns, which may be interconnected.
Array	A data structure for software elements where each element has a unique identifying index number.
Server	A computer system in a network whose services may be invoked by one or more clients.
Client	A computer program or terminal that requests information or services from another computer (a server) on the network.
Standalone application	A computer program capable of operating without external resources.
Astropy	A community Python Library for Astronomy. Astropy aims to enable the community to develop a robust ecosystem of affiliated packages covering a broad range of needs for astronomical research, data processing, and data analysis. See also PyVO
Database management system	A collection of programs that enables storage, modification, and information extraction from a database. Also see RDBMS.
Proxy certificate	A certificate that is used in the place of another, typically with a limited lifetime.
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Namespace	1. The set of names in a naming system. 2. In XML, a collection of names, identified by a URI reference, that are used in XML documents as element types and attribute names.
Attributes	1. In XML, characteristics of an element that are specified within the
Element	1. A single item in an array. 2. In XML, a node in document. Each element starts with a and ends with.
Schema	1. A description of the structure and rules an XML document must satisfy. 2. In SQL, a description of the tables and columns in the database.
YAML	(YAML Ain’t Markup Language) A data serialization language based on XML and other languages.
XML-RPC	(XML-Remote Procedure Call) A web service protocol that utilizes XML technology to implement an RPC protocol.
XPath	(XML Path Language) a language that describes how to locate specific content within an XML document.
XOP	(XML Binary Optimized Packaging) A standard specifying how binary data should be represented in XML.
W3C	(World Wide Web Consortium) An international consortium where member organizations, a full-time staff, and the public work together to develop web standards.
WCS	(World Coordinate System) A detailed specification of the conversion between coordinates within a file and physical coordinates, especially between pixel and celestial coordinates in an image.
WSDL	(Web Services Description Language) An XML document that describes and locates a web service.
URL	(Uniform Resource Locator) The global address of documents and other resources on the World Wide Web. The first part of the address specifies the protocol to be used when accessing the resource, the remainder describes its network location.
URI	(Uniform Resource Identifier) An address standard for a resource available on the Internet.
UCD	(Unified Content Descriptors) A formal vocabulary for astronomical data that is controlled by the IVOA.
TOPCAT	(Tool for OPerations on Catalogs And Tables) An interactive graphical viewer and editor for tabular data, designed for but not limited to astronomical tables.
TLA	(Three Letter Acronym) A tribute to the use of acronyms in the computer field.
SQL	(Structured Query Language) The standard language used to communicate with RDBMS s
SRB	(Storage Resource Broker) Middleware developed at the San Diego Supercomputing Center that provides standardized access to a number of very large data resources.
STILTS	(STIL Tool Set) A set of VO tools for processing of tabular data based on the UK Starlink Tables Infrastructure.
STC	(Space-Time Coordinates) An IVOA standard for describing a region or position in both space and time.
SExtractor	(Source Extractor) A tool that detects sources in astronomical images.
SSDL	(SOAP Service Description Language) SSDL is a SOAP -centric description language for web services that enables protocol -based integration.
SimDM	(Simulation Data Model) describes numerical computer simulations of astrophysical systems.
SSAP	(Simple Spectral Access Protocol) A protocol that returns a set of spectra in a specified region of the sky. Similar to SIA but has many more options.
SOAP	(Simple Object Access Protocol) A protocol for invoking remote services by exchanging XML -based messages.
SMTP	(Simple Mail Transfer Protocol) A protocol used to send and receive email.
SIA, SIAP	(Simple Image Access Protocol) A VO protocol that supports queries for images available in a given data collection near a given position on the sky.
SAX	(Simple API for XML) A standardized interface for parsing XML documents using callbacks.
SIMBAD	(Set of Identifications, Measurements and Bibliography for Astronomical Data) An astronomical database provides extensive information on both galactic and extragalactic objects. SIMBAD also provides a name resolver.
SOA	(Service Oriented Architecture) An approach to distributed computing that focuses on services that communicate with each other.
SSL	(Secure Sockets Layer) A protocol for managing the security of a message transmission over the Internet.
RSS	(Rich Site Summary). An XML format for sharing content among different Web sites such as news items.
RDF	(Resource Description Framework) A recommendation from the W3C for creating metadata structures that define data on the web.
ROME	(Request-Object Management Environment) A VO tool to manage the execution of a task that requires many subtasks.
REST	(Representational State Transfer) An approach to web services that uses the standard HTTP GET and POST protocols.
RPC	(Remote Procedure Call) Protocols for distributed computing where the interaction is represented as the client computer invoking discrete services/calls on the server.
RMI	(Remote Method Invocation) A Java protocol for distributed computing.
RDBMS	(Relational DataBase? Management System) A DBMS that uses represents data using a relational database.
PLASTIC	(PLatform for AStronomical Tool InterConnection? ) A protocol that allows collaboration between multiple processes running on the user’s desktop.
PHP	(PHP
OAI	(Open Archive Initiative) A protocol that defines an interface for the sharing of metadata.
OASIS	(On-line Archive Science Information Services) A VO Tool to access and display astronomical image and catalog data.
NESSSI	(NVO Extensible Scalable Secure Service Infrastructure) A VO web service that runs secure, asynchronous services on the Grid.
NED	(NASA Extragalactic Database) An astronomical resource containing extensive information on extragalactic objects. NED also provides a name resolver.
MIME	(Multipurpose Internet Mail Extensions) The most common protocol for encoding, transmitting, and decoding non-text files via e-mail.
JDBC	(Java Database Connectivity) The standard Java interface for access to SQL -based DBMS ’s.
IVOA	(International Virtual Observatory Alliance) An international collaboration formed in June 2002 to coordinate Virtual Observatory activities worldwide.
IDL	(Interactive Data Language) A popular data analysis programming language used by scientists.
IRAF	(Image Reduction and Analysis Facility) A software system for astronomical data analysis including both tools, libraries and languages developed primarily at the National Optica Astronomy Observatories (NOAO).
HTML	(Hypertext Markup Language) A standard document format used on most web pages which makes it easy for one document to refer to another.
HPC	(High Performance Computing) Typically refers to supercomputers used in scientific research.
GUI	(Graphical User Interface) A graphics-based user interface that incorporates movable windows, icons and a mouse.
GPL	(GNU Public License) A software license which allows for redistribution but requires both original and modified source code to be made available.
FITS	(Flexible Image Transport System) The IAU-approved standard format for astronomical data.
FTP	(File Transfer Protocol) A protocol used to exchange files over the internet.
XSL	(eXtensible Stylesheet Language) A standard for describing how to transform XML documents into other documents in either XML or other formats.
XSLT	(eXtensible Stylesheet Language Transformations) A conversion tool that implements XSL.
XML	(eXtensible Markup Language) A markup language that provides a file format for representing data.
DHCP	(Dynamic Host Configuration Protocol) A protocol that automatically manages IP addresses for a set of nodes in a network.
DOM	(Document Object Model) A W3C standard in which a structured document such as an XML file is viewed as a tree of elements.
DCOM	(Distributed Common Object Model) A protocol that allows communication and manipulation of objects over a network connection.
DAL	(Data Access Layer) The VO protocols that define how VO applications access data resources. Data Access Layer Working Group
CORBA	(Common Object Request Broker Architecture) An open, vendor-independent architecture and infrastructure that computer applications use to work together over networks.
CGI	(Common Gateway Interface) A protocol that defines how data is passed to server applications using HTTP.
AJAX	(Asynchronous Javascript + XML) A framework for adding dynamic interactions within web pages.
ADQL	(Astronomical Data Query Language) is the language used by the International Virtual Observatory Alliance (IVOA) to represent astronomy queries posted to VO services. ADQL is based on the Structured Query Language (SQL), especially on SQL 92. The VO has a number of tabular data sets and many of them are stored in relational databases, making SQL a convenient access means. A subset of the SQL grammar has been extended to support queries that are specific to astronomy.
API	(Application Programming Interface) The documentation of the interface to a software library or tool.
ASCII	(American Standard Code for Information Interchange) Formally, an encoding of common alphanumeric symbols. Often used to mean a human readable representation with no ‘special’ characters or formatting.
ASP	(Active Server Pages) A technology that enables dynamic web pages using server -side scripting.