DMTN-302

IVOA Identifier Usage at the Rubin Observatory

This is a draft.

By:

• Tim Jenness

Abstract

The IVOA define a standard URI scheme to reference individual datasets. In this document we will define how these IVOA Identifiers will be formed for Butler datasets and possibly object catalog IDs.

Introduction

The IVOA Identifier (IVOID) standard [Demleitner et al., 2016] provides a mechanism for publishers to provide unique identifiers to individual datasets using an ivo URI scheme. The IVOID consists of a registry part that must be registered in VO Registry, and a local part that defines the specific resource. The registry part consists of a naming authority (effectively an internet location corresponding to the netloc field) and a resource key (corresponding to the path). The local part corresponds to the query component of a URI and can additional be fine-tuned by the use of a fragment. This document will address the naming authority, resource key, and query parts of the URI.

Naming Authority

There is no requirement that the naming authority component correspond to a public web site since the value is looked up in the VO Registry. Indeed, IVOA recommendation is to deliberately avoid using a website with examples given such as ivo://org.gavo.dc/ (reversing the internet address) and ivo://adil.ncsa (publishing organization and archive).

This suggests Rubin should consider:

• lsst.rubin

• rubin.lsst

• org.lsst

• org.rubinobservatory

• org.rubinobs

If lsst is in the authority name that implies we would change the authority name in the future for some potential non-LSST survey in the late 2030s.

Resource Key

The resource key allows us to segregate our registry entries. For example we could do what GAVO does and use ~ to indicate that all our resources are using a single registry entry. Alternatively we could segregate by butler datasets vs catalog content or have a resource per data release.

• ~

• butler

• datasets

• lsst

• lsst-dr1

• catalog

Query

The query part of the IVOID indicates how a specific dataset should be referenced. In theory this could be the Butler dataset UUID or the source/object catalog ID without any other information. In practice we would not want to look in all possible butler repositories for a matching dataset ID and so the Butler label should be included (assuming we aren’t encoding the butler repository in the resource key section).

• ?dr1/UUID

• ?/repo/main/UUID

• ?butler/dp1/UUID

As can be seen from the previous section it is still unclear whether butler?dr1/UUID, butler/dr1?UUID or lsst?butler/dr1/UUID are preferred.

All our catalog IDs encode the data release and the catalog entry type (source vs object vs DIA variants) within them so there is no requirement for a data release to be explicitly included or to note whether it is a source or not. From a readability perspective it would help if that information was included.

• ?object/dr1/1234567890

• ?source/dr1/1234567890

An alternative is to explicitly use keyword/value form:

• ?repo=/repo/main&id=UUID

• ?type=object&release=dr1&id=OBJECT_ID

Putting it All Together

The previous sections would suggest that a butler IVOID could look like:

• ivo://rubin.lsst/datasets?dr1/UUID

• ivo://rubin.lsst/catalog?source/dr1/SOURCE_ID

References

[1]

Markus Demleitner, Raymond Plante, Tony Linde, Roy Williams, and Keith Noddle. IVOA Identifiers Version 2.0. IVOA Recommendation 23 May 2016, May 2016. arXiv:1605.07501, doi:10.5479/ADS/bib/2016ivoa.spec.0523D.