Although Diamond Open Access is gaining momentum as a more equitable, fair, inclusive publishing model, there is no universal definition yet of Diamond OA journals. Most prevalent is defining them by zero APC (article processing charges). There’s widespread understanding that absence of APC’s is not enough and that Diamond OA journals should be owned by scientists, academic institutions or research infrastructures and be operated professionally, based on values of research integrity. Thus, Diamond OA is considered to be a positive alternative to economic distortions parts of the open access publishing market display. The DIAMAS and CRAFT-OA projects introduced operational criteria to identify Diamond OA journals. They are required to enable binary decisions of journals classifying as Diamond OA or not within the Diamond Discovery Hub (DDH), a registry for such journals launching by the end of 2025. DDH will be a responsive, scalable platform with SEO-friendly UI, based on an editorial model including trusted data sources of Diamond OA journals on one side and a DDH editorial team on the other. The editorial team will be volunteers, organised along the emerging system of Diamond Capacity Centres and a central Diamond Capacity Hub. Trusted sources will mostly be European institutional publishing service providers (IPSPs). The DDH will support decision making of authors, funders or institutions and bring more visibility and recognition to Diamond OA journals and the Diamond OA model in general. Therefore, inclusion criteria have to be based on observable data points and be as unambiguous and transparent as possible. They are:1. use of persistent identifier2. being a scientific journal3. immediate Open Access with open licences4. no fees5. open to all authors within a journal’s scope6. community-ownedWhile criteria 1 and 3 are machine-observable data points and for 2, 4, and 5 approved practices exist, criteria 6 on (scientific) community ownership is challenging to base binary decisions on. If parameters of judging “community owned” are set too wide, the rigorousness of such a collection is watered down with too many questionable entries. If set too narrow, the DDH would risk excluding scientific journals identifying with the overall goals of Diamond OA but failing to meet minor aspects of “community owned”. We’d like to facilitate a community effort in developing flexible, transparent parameters for criteria 6. These parameters will help in two ways: journals identifying with values and ethics of Diamond OA find guidance in how to express this in an observable manner while clear parameters enable the volunteers’ work within the DDH editorial team. We propose a 90-minute workshop to jointly work on the mentioned parameters of criteria 6 around community-ownership. To give participants a hands-on experience we’ll introduce the DDH’s current alpha-version system and our planned editorial model.