A widely used metric for assessing the quality of a workshop/conference is the acceptance rate. The lower the acceptance rate, the higher the presumable quality, since it indicates a rigorous peer review.
Many editors of volume at CEUR-WS.org include such data (number of submissions, number of accepted papers) in their preface.
So, why not include it as semantic annotation into the main index file of a published volume. This would allow to query a volume on basis of such metrics, e.g. “give me all volumes with an acceptance rate lower than 25% for full papers”.
Are there standards available to represent such data, e.g. in RDF?