I am part of a committee tasked to create a policy on creating incentives for publications of university employees. Right now, the highest incentive award is given to publications in journals "indexed in Web of Science or Scopus." I would like to rewrite the policy so that it is more general, that is, open to the possibility that there are other highly regarded bibliographic database and index services. I am aware that there are many predatory journal indexing services, and I want to exclude these.
How do I define a reputable journal indexing service?