While it is true that the adoption of SKOS will make it easy to publish and access different astronomical vocabularies, the fact is that there is no vocabulary which makes it easy to jump-start the use of vocabularies in generic astrophysical VO applications: each of the previously developed vocabularies has their own limits and biases. For example, the IAU Thesaurus provides a large number of entries, copious relationships, and translations to four other languages, but there are no definitions, many concepts are now only useful for historical purposes (for example many photographic or historical instrument entries), some of the relationships are false or outdated, and many important or newer concepts and their common abbreviations are missing.
Despite its faults, the IAU Thesaurus constitutes a very extensive vocabulary which could easily serve as the basis vocabulary once we have removed its most egregious faults and extended it to cover the most obvious semantic holes. To this end, a heavily revised IAU thesaurus is in preparation for use within the IVOA and other astronomical contexts.