Other databases say they curate their indexing list to avoid predatory publishers and they probably do a good job at that, but at the consequence of systematically avoiding fields where the peer-review standards differ from STEM fields (e.g., social sciences, business, law, humanities, arts, etc). These same criteria also exclude quality research in non-English languages and of regional focus. Our approach is to be inclusive and allow users to filter out undesirable sources.
Predatory journals and deceptive conferences are especially thorny issues because folks do not agree on an authoritative list; they change over time; and there is a massive range of predatory behaviours that some include in their definition and others do not. Faked peer review is obviously problematic. But others define predatory journals as any journal whose publisher trades quality of publication in peer review for business purposes. That behaviour includes journals from for-profit publishers where companies tell editorial boards to arbitrarily increase the volume of accepted works for fiscal goals (common practice in 'reputable sources').
On the other hand, we have a couple of universities who have identified their own lists of deceptive publishers and are using OpenAlex data to understand trends in those publishers in order to plan, implement, and evaluate their strategy to support researchers against deceptive publishers. Without the ability to analyze these publishers, counter-measures to protect researchers and the integrity of science are difficult.
While we aim to be as inclusive as possible and let folks choose what to exclude from their analyses, we also know it is more complicated than most users will want to learn and that we need to support them as well. Likewise, we have implemented filters that help users narrow the results they might find relating to source 'trustworthiness': indexed in DOAJ and included in CWTS Core sources list.
Because of the open nature of our database, a list of journals to exclude can easily be developed by one user and shared with others at their institution. So if you have questions about which sources you might want to exclude from an analysis, check with your local librarian to see if they've curated such a list. As the community continues to build broader consensus on trusted publishing sources, we'll continue to add more filters like the two above directly into the OpenAlex API and user interface.