IVOA Recommendation: An IVOA Standard for Unified Content Descriptors Version 1.1

TL;DR

This paper introduces UCD1+, a new standard for describing astronomical data quantities using a controlled vocabulary, improving upon the previous UCD1 standard with a new syntax and easier software adaptation.

Contribution

It defines the UCD1+ standard, enhancing the syntax and vocabulary for astronomical data description, and provides guidelines for maintenance and evolution.

Findings

UCD1+ standard improves data description consistency.

Tools and use cases for UCD1+ are provided.

UCD1+ facilitates software adaptation with minimal effort.

Abstract

This document describes the current understanding of the IVOA controlled vocabulary for describing astronomical data quantities, called Unified Content Descriptors (UCDs). The present document defines a new standard (named UCD1+) improving the first generation of UCDs (hereafter UCD1). The basic idea is to adopt a new syntax and vocabulary requiring little effort for people to adapt softwares already using UCD1. This document also addresses the questions of maintenance and evolution of the UCD1+. Examples of use cases within the VO, and tools for using UCD1+ are also described.