Registry-Related Namespaces

While XML namespace prefixes are by design flexible, there are several namespaces used in registry resource documents that are generally agreed upon within the IVOA. These are each described in the registry extensions section of each descriptive documents in the IVOA Document Repository. For convenience, a short summary is provided here. The list is primarily populated from the Registry Table Access Protocol standard document, but also contains retired/deprecated types that may be seen in active registry resources. This list is maintained by the Registry Working Group; please contact the chair or vice-chair if it appears out of date.

Note that documents may or may not reference minor version numbers ahead of a .0 document version. Minor versions of IVOA documents are designed to be backward-compatible in schema within their major version number. Therefore to avoid additional operations/curation effort with each minor document, we do not require registry resources to reference the newest document unless updating to a major version number.

Namespace	Resource Type Described, if any	Current canonical, resolvable location	Prior versions that may still exist and appear in registries
vr	Resource	http://www.ivoa.net/xml/VOResource/v1.0
ri	Resource	http://www.ivoa.net/xml/RegistryInterface/v1.0
vs	DataService	http://www.ivoa.net/xml/VODataService/v1.1	http://www.ivoa.net/xml/VODataService/v1.0
uws	(not a resource type: Universal Worker Service)	http://www.ivoa.net/xml/UWS/v1.0
cap	(not a resource type: VOSI capability)	http://www.ivoa.net/xml/VOSICapabilities/v1.0
stc	(not a resource type)	http://www.ivoa.net/xml/STC/stc-v1.30.xsd
oai	(not a resource type)	http://www.openarchives.org/OAI/2.0/
oai_dc	(not a resource type)	http://www.openarchives.org/OAI/2.0/oai_dc/
dc	(not a resource type)	http://purl.org/dc/elements/1.1/
vg	Registry	http://www.ivoa.net/xml/VORegistry/v1.0
cs	ConeSearch	http://www.ivoa.net/xml/ConeSearch/1.0
sia	SimpleImageAccess	http://www.ivoa.net/xml/SIA/v1.1	http://www.ivoa.net/xml/SIA/v1.0
ssap*	SimpleSpectralAccess	http://www.ivoa.net/xml/SSA/v1.1	http://www.ivoa.net/xml/SSA/v1.0 or http://www.ivoa.net/xml/SSA/v0.4
sn or osn	OpenSkyNode (deprecated)	(deprecated)	http://www.ivoa.net/xml/OpenSkyNode/v0.2
tr	TAP	http://www.ivoa.net/xml/TAPRegExt/v1.0
slap	SimpleLineAccess	http://www.ivoa.net/xml/SLAP/v1.0
vstd	VOStandard	http://www.ivoa.net/xml/StandardsRegExt/v1.0
xsi	(not a resource type)	http://www.w3.org/2001/XMLSchema-instance
xsd	(not a resource type)	http://www.w3.org/2001/XMLSchema
xlink	(not a resource type)	http://www.w3.org/1999/xlink

* ssap is the canonical namespace moving forward, not ssa, although ssa is commonly used in registries. "ssa" is used elsewhere regarding utypes.